diff --git a/benchmark/src/androidTest/java/com/vitorpamplona/quartz/benchmark/ChaCha20Benchmark.kt b/benchmark/src/androidTest/java/com/vitorpamplona/quartz/benchmark/ChaCha20Benchmark.kt
index 296a8927f..2f39dcc55 100644
--- a/benchmark/src/androidTest/java/com/vitorpamplona/quartz/benchmark/ChaCha20Benchmark.kt
+++ b/benchmark/src/androidTest/java/com/vitorpamplona/quartz/benchmark/ChaCha20Benchmark.kt
@@ -52,36 +52,16 @@ class ChaCha20Benchmark {
     }
 
     @Test
-    fun encryptLibSodium() {
+    fun encrypt() {
         benchmarkRule.measureRepeated {
-            chaCha.encryptLibSodium(padded, messageKeys.chachaNonce, messageKeys.chachaKey)
+            chaCha.encrypt(padded, messageKeys.chachaNonce, messageKeys.chachaKey)
         }
     }
 
-    /*
-        Removed in the conversion to KMP
     @Test
-    fun encryptNative() {
+    fun decrypt() {
         benchmarkRule.measureRepeated {
-            chaCha.encryptNative(padded, messageKeys.chachaNonce, messageKeys.chachaKey)
+            chaCha.decrypt(padded, messageKeys.chachaNonce, messageKeys.chachaKey)
         }
     }
-     */
-
-    @Test
-    fun decryptLibSodium() {
-        benchmarkRule.measureRepeated {
-            chaCha.decryptLibSodium(padded, messageKeys.chachaNonce, messageKeys.chachaKey)
-        }
-    }
-
-    /*
-    Removed in the conversion to KMP
-    @Test
-    fun decryptNative() {
-        benchmarkRule.measureRepeated {
-            chaCha.decryptNative(padded, messageKeys.chachaNonce, messageKeys.chachaKey)
-        }
-    }
-     */
 }
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 0323197d2..eeba3e5e5 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -25,7 +25,6 @@ fragmentKtx = "1.8.9"
 gms = "4.4.4"
 jacksonModuleKotlin = "2.21.1"
 javaKeyring = "1.0.4"
-jna = "5.18.1"
 jtorctl = "0.4.5.7"
 junit = "4.13.2"
 kchesslib = "1.0.5"
@@ -34,8 +33,6 @@ kotlinxCollectionsImmutable = "0.4.0"
 kotlinxCoroutinesCore = "1.10.2"
 kotlinxSerialization = "1.10.0"
 languageId = "17.0.6"
-lazysodiumAndroid = "5.2.0"
-lazysodiumJava = "5.2.0"
 lifecycleRuntimeKtx = "2.10.0"
 lightcompressor-enhanced = "1.6.0"
 markdown = "f92ef49c9d"
@@ -144,7 +141,6 @@ google-mlkit-language-id = { group = "com.google.mlkit", name = "language-id", v
 google-mlkit-translate = { group = "com.google.mlkit", name = "translate", version.ref = "translate" }
 jackson-module-kotlin = { group = "com.fasterxml.jackson.module", name = "jackson-module-kotlin", version.ref = "jacksonModuleKotlin" }
 java-keyring = { group = "com.github.javakeyring", name = "java-keyring", version.ref = "javaKeyring" }
-jna = { group = "net.java.dev.jna", name = "jna", version.ref = "jna" }
 jtorctl = { module = "info.guardianproject:jtorctl", version.ref = "jtorctl" }
 junit = { group = "junit", name = "junit", version.ref = "junit" }
 kchesslib = { module = "io.github.cvb941:kchesslib", version.ref = "kchesslib" }
@@ -153,8 +149,6 @@ kotlinx-coroutines-core = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-c
 kotlinx-coroutines-swing = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-swing", version.ref = "kotlinxCoroutinesCore" }
 kotlinx-serialization-json = { module = "org.jetbrains.kotlinx:kotlinx-serialization-json", version.ref = "kotlinxSerialization" }
 kotlinx-serialization-cbor = { module = "org.jetbrains.kotlinx:kotlinx-serialization-cbor", version.ref = "kotlinxSerialization" }
-lazysodium-java = { group = "com.goterl", name = "lazysodium-java", version.ref = "lazysodiumJava" }
-lazysodium-android = { group = "com.goterl", name = "lazysodium-android", version.ref = "lazysodiumAndroid" }
 markdown-commonmark = { group = "com.github.vitorpamplona.compose-richtext", name = "richtext-commonmark", version.ref = "markdown" }
 markdown-ui = { group = "com.github.vitorpamplona.compose-richtext", name = "richtext-ui", version.ref = "markdown" }
 markdown-ui-material3 = { group = "com.github.vitorpamplona.compose-richtext", name = "richtext-ui-material3", version.ref = "markdown" }
diff --git a/quartz/build.gradle.kts b/quartz/build.gradle.kts
index da7c363a9..1ed25d82e 100644
--- a/quartz/build.gradle.kts
+++ b/quartz/build.gradle.kts
@@ -63,65 +63,11 @@ kotlin {
     // project can be found here:
     // https://developer.android.com/kotlin/multiplatform/migrate
     val xcfName = "quartz-kmpKit"
-    val libsodiumPath = project.file("src/nativeInterop/libsodium")
-    val libsodiumHeaderFilesPath = project.file("$libsodiumPath/include/sodium")
-
-    // Generate target-specific Libsodium definition files for creating native bindings.
-    // Device (iosArm64) uses libsodium.a, simulator targets use libsodium-simulator.a.
-    val libsodiumDeviceDefFile =
-        project.layout.buildDirectory
-            .file("cinterop/Clibsodium-device.def")
-            .get()
-            .asFile
-    val libsodiumSimulatorDefFile =
-        project.layout.buildDirectory
-            .file("cinterop/Clibsodium-simulator.def")
-            .get()
-            .asFile
-
-    // This generates the Libsodium definition file, necessary for creating native bindings(a Kotlin API) for libsodium(for iOS).
-    val libsodiumDefFileGeneration =
-        tasks.register("GenerateSodiumCinteropFile") {
-            outputs.files(libsodiumDeviceDefFile, libsodiumSimulatorDefFile)
-            doLast {
-                libsodiumDeviceDefFile.parentFile.mkdirs()
-                libsodiumDeviceDefFile.writeText(
-                    "package = Clibsodium\n" +
-                        "staticLibraries = libsodium.a\n" +
-                        "libraryPaths = ${libsodiumPath.absolutePath}/ios/lib\n",
-                )
-                libsodiumSimulatorDefFile.writeText(
-                    "package = Clibsodium\n" +
-                        "staticLibraries = libsodium-simulator.a\n" +
-                        "libraryPaths = ${libsodiumPath.absolutePath}/ios-simulators/lib\n",
-                )
-            }
-        }
 
     listOf(
         iosArm64(),
         iosSimulatorArm64(),
     ).forEach { target ->
-        val isSimulator = target.name != "iosArm64"
-        val defFile = if (isSimulator) libsodiumSimulatorDefFile else libsodiumDeviceDefFile
-
-        target.compilations.getByName("main") {
-            val clibsodium by cinterops.creating {
-                definitionFile = defFile
-                packageName = "Clibsodium"
-
-                headers(
-                    "$libsodiumHeaderFilesPath/crypto_aead_xchacha20poly1305.h",
-                    "$libsodiumHeaderFilesPath/crypto_core_hchacha20.h",
-                    "$libsodiumHeaderFilesPath/crypto_stream_chacha20.h",
-                )
-            }
-
-            tasks.named(cinterops.getByName("clibsodium").interopProcessingTaskName).configure {
-                dependsOn(libsodiumDefFileGeneration)
-            }
-        }
-
         target.swiftPackageConfig(cinteropName = "swiftbridge") {
             minIos = "17"
             minMacos = "14"
@@ -139,9 +85,6 @@ kotlin {
     }
 
     iosArm64 {
-        binaries.all {
-            linkerOpts("-L${libsodiumPath.absolutePath}/ios/lib", "-lsodium")
-        }
         binaries.framework {
             baseName = xcfName
             binaryOption("bundleId", "com.vitorpamplona.quartz")
@@ -149,9 +92,6 @@ kotlin {
     }
 
     iosSimulatorArm64 {
-        binaries.all {
-            linkerOpts("-L${libsodiumPath.absolutePath}/ios-simulators/lib", "-lsodium-simulator")
-        }
         binaries.framework {
             baseName = xcfName
             binaryOption("bundleId", "com.vitorpamplona.quartz")
@@ -254,9 +194,6 @@ kotlin {
                 // Bitcoin secp256k1 bindings
                 implementation(libs.secp256k1.kmp.jni.jvm)
 
-                // LibSodium for ChaCha encryption (NIP-44)
-                implementation(libs.lazysodium.java)
-                implementation(libs.jna)
             }
         }
 
@@ -279,9 +216,6 @@ kotlin {
                 // Bitcoin secp256k1 bindings to Android
                 api(libs.secp256k1.kmp.jni.android)
 
-                // LibSodium for ChaCha encryption (NIP-44)
-                implementation("com.goterl:lazysodium-android:5.2.0@aar")
-                implementation("net.java.dev.jna:jna:5.18.1@aar")
             }
         }
 
@@ -293,9 +227,6 @@ kotlin {
                 // Bitcoin secp256k1 bindings
                 implementation(libs.secp256k1.kmp.jni.jvm)
 
-                // LibSodium for ChaCha encryption (NIP-44) - Needed for host tests
-                implementation(libs.lazysodium.java)
-                implementation(libs.jna)
 
                 // SQLite bundled driver for Host tests
                 implementation(libs.androidx.sqlite.bundled.jvm)
@@ -315,9 +246,6 @@ kotlin {
                 // Bitcoin secp256k1 bindings to Android
                 api(libs.secp256k1.kmp.jni.android)
 
-                // LibSodium for ChaCha encryption (NIP-44)
-                implementation("com.goterl:lazysodium-android:5.2.0@aar")
-                implementation("net.java.dev.jna:jna:5.18.1@aar")
             }
         }
 
diff --git a/quartz/consumer-rules.pro b/quartz/consumer-rules.pro
index 4985bd413..04373ed53 100644
--- a/quartz/consumer-rules.pro
+++ b/quartz/consumer-rules.pro
@@ -16,32 +16,10 @@
 # preserve access to native classses
 -keep class fr.acinq.secp256k1.** { *; }
 
-# JNA For Libsodium
--keep class com.goterl.lazysodium.** { *; }
-
 # libscrypt
 -keep class com.lambdaworks.codec.** { *; }
 -keep class com.lambdaworks.crypto.** { *; }
 -keep class com.lambdaworks.jni.** { *; }
 
-# JNA also requires AWT, which Android does not have. So the classes are broken down to filter AWT out
--keep class com.sun.jna.ToNativeConverter { *; }
--keep class com.sun.jna.NativeMapped { *; }
--keep class com.sun.jna.CallbackReference { *; }
--keep class com.sun.jna.ptr.IntByReference { *; }
--keep class com.sun.jna.NativeLong { *; }
--keep class com.sun.jna.Structure { *; }
--keep class com.sun.jna.Structure$* { *; }
--keep class com.sun.jna.Native$ffi_callback { *; }
--keep class * implements com.sun.jna.Structure$* { *; }
--keep class * implements com.sun.jna.Native$* { *; }
--keep class com.sun.jna.Native {
-    private static com.sun.jna.NativeMapped fromNative(java.lang.Class, java.lang.Object);
-    private static com.sun.jna.NativeMapped fromNative(java.lang.reflect.Method, java.lang.Object);
-    private static java.lang.Class nativeType(java.lang.Class);
-    private static java.lang.Object toNative(com.sun.jna.ToNativeConverter, java.lang.Object);
-    private static java.lang.Object fromNative(com.sun.jna.FromNativeConverter, java.lang.Object, java.lang.reflect.Method);
-}
-
 # JSON parsing
 -keep class com.vitorpamplona.quartz.** { *; }
\ No newline at end of file
diff --git a/quartz/proguard-rules.pro b/quartz/proguard-rules.pro
index 4d9f471e2..e1f545f4d 100644
--- a/quartz/proguard-rules.pro
+++ b/quartz/proguard-rules.pro
@@ -30,33 +30,11 @@
 # preserve access to native classses
 -keep class fr.acinq.secp256k1.** { *; }
 
-# JNA For Libsodium
--keep class com.goterl.lazysodium.** { *; }
-
 # libscrypt
 -keep class com.lambdaworks.codec.** { *; }
 -keep class com.lambdaworks.crypto.** { *; }
 -keep class com.lambdaworks.jni.** { *; }
 
-# JNA also requires AWT, which Android does not have. So the classes are broken down to filter AWT out
--keep class com.sun.jna.ToNativeConverter { *; }
--keep class com.sun.jna.NativeMapped { *; }
--keep class com.sun.jna.CallbackReference { *; }
--keep class com.sun.jna.ptr.IntByReference { *; }
--keep class com.sun.jna.NativeLong { *; }
--keep class com.sun.jna.Structure { *; }
--keep class com.sun.jna.Structure$* { *; }
--keep class com.sun.jna.Native$ffi_callback { *; }
--keep class * implements com.sun.jna.Structure$* { *; }
--keep class * implements com.sun.jna.Native$* { *; }
--keep class com.sun.jna.Native {
-    private static com.sun.jna.NativeMapped fromNative(java.lang.Class, java.lang.Object);
-    private static com.sun.jna.NativeMapped fromNative(java.lang.reflect.Method, java.lang.Object);
-    private static java.lang.Class nativeType(java.lang.Class);
-    private static java.lang.Object toNative(com.sun.jna.ToNativeConverter, java.lang.Object);
-    private static java.lang.Object fromNative(com.sun.jna.FromNativeConverter, java.lang.Object, java.lang.reflect.Method);
-}
-
 # JSON parsing
 -keep class com.vitorpamplona.quartz.** { *; }
 
diff --git a/quartz/src/androidMain/kotlin/com/vitorpamplona/quartz/utils/LibSodiumInstance.android.kt b/quartz/src/androidMain/kotlin/com/vitorpamplona/quartz/utils/LibSodiumInstance.android.kt
deleted file mode 100644
index 7bfa83a2f..000000000
--- a/quartz/src/androidMain/kotlin/com/vitorpamplona/quartz/utils/LibSodiumInstance.android.kt
+++ /dev/null
@@ -1,131 +0,0 @@
-/*
- * Copyright (c) 2025 Vitor Pamplona
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy of
- * this software and associated documentation files (the "Software"), to deal in
- * the Software without restriction, including without limitation the rights to use,
- * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
- * Software, and to permit persons to whom the Software is furnished to do so,
- * subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in all
- * copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
- * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
- * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
- * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
- * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
- */
-package com.vitorpamplona.quartz.utils
-
-import com.goterl.lazysodium.LazySodium
-import com.goterl.lazysodium.LazySodiumAndroid
-import com.goterl.lazysodium.Sodium
-import com.goterl.lazysodium.SodiumAndroid
-
-actual object LibSodiumInstance {
-    private val libSodium: Sodium =
-        try {
-            // If we are running in a host test, SodiumJava might be available.
-            // SodiumJava uses a ResourceLoader to find the dylib/so/dll in the jar.
-            Class
-                .forName("com.goterl.lazysodium.SodiumJava")
-                .getConstructor()
-                .newInstance() as Sodium
-        } catch (_: Exception) {
-            SodiumAndroid()
-        }
-
-    private val lazySodium: LazySodium =
-        if (libSodium is SodiumAndroid) {
-            LazySodiumAndroid(libSodium)
-        } else {
-            // this should only happen on test cases
-            val sodiumJava =
-                Class
-                    .forName("com.goterl.lazysodium.SodiumJava")
-
-            Class
-                .forName("com.goterl.lazysodium.LazySodiumJava")
-                .getConstructor(sodiumJava)
-                .newInstance(libSodium) as LazySodium
-        }
-
-    actual fun cryptoAeadXChaCha20Poly1305IetfDecrypt(
-        message: ByteArray,
-        nSec: ByteArray,
-        ciphertext: ByteArray,
-        ad: ByteArray,
-        nPub: ByteArray,
-        k: ByteArray,
-    ): Boolean =
-        lazySodium.cryptoAeadXChaCha20Poly1305IetfDecrypt(
-            message,
-            longArrayOf(message.size.toLong()),
-            nSec,
-            ciphertext,
-            ciphertext.size.toLong(),
-            ad,
-            ad.size.toLong(),
-            nPub,
-            k,
-        )
-
-    actual fun cryptoAeadXChaCha20Poly1305IetfEncrypt(
-        ciphertext: ByteArray,
-        message: ByteArray,
-        ad: ByteArray,
-        nSec: ByteArray,
-        nPub: ByteArray,
-        k: ByteArray,
-    ): Boolean =
-        lazySodium.cryptoAeadXChaCha20Poly1305IetfEncrypt(
-            ciphertext,
-            longArrayOf(ciphertext.size.toLong()),
-            message,
-            message.size.toLong(),
-            ad,
-            ad.size.toLong(),
-            nSec,
-            nPub,
-            k,
-        )
-
-    actual fun cryptoStreamChaCha20IetfXor(
-        message: ByteArray,
-        nonce: ByteArray?,
-        key: ByteArray?,
-    ): ByteArray {
-        val ciphertext = ByteArray(message.size)
-        lazySodium.cryptoStreamChaCha20IetfXor(ciphertext, message, message.size.toLong(), nonce, key)
-        return ciphertext
-    }
-
-    // This function wasn't available in the bindings library. I had to move them here from C
-    actual fun cryptoStreamXChaCha20Xor(
-        messageBytes: ByteArray,
-        nonce: ByteArray,
-        key: ByteArray,
-    ): ByteArray {
-        val cipher = ByteArray(messageBytes.size)
-        val k2 = ByteArray(32)
-
-        val nonceChaCha = nonce.drop(16).toByteArray()
-        assert(nonceChaCha.size == 8)
-
-        libSodium.crypto_core_hchacha20(k2, nonce, key, null)
-        val resultCode =
-            libSodium.crypto_stream_chacha20_xor_ic(
-                cipher,
-                messageBytes,
-                messageBytes.size.toLong(),
-                nonceChaCha,
-                0,
-                k2,
-            )
-
-        return if (resultCode == 0) cipher else throw IllegalStateException("Could not decrypt message")
-    }
-}
diff --git a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/ChaCha20.kt b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/ChaCha20.kt
index 3fe570a86..1cbf72a8a 100644
--- a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/ChaCha20.kt
+++ b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/ChaCha20.kt
@@ -20,55 +20,16 @@
  */
 package com.vitorpamplona.quartz.nip44Encryption.crypto
 
-import com.vitorpamplona.quartz.utils.LibSodiumInstance
-
-/**
- * Encapsulates the ChaCha20 options. LibSodium is faster on real hardware: 851ns vs 2,535ns encrypt/decrypt times
- */
 class ChaCha20 {
     fun encrypt(
         message: ByteArray,
         nonce: ByteArray,
         key: ByteArray,
-    ) = encryptLibSodium(message, nonce, key)
+    ) = ChaCha20Core.chaCha20Xor(message, key, nonce, counter = 0)
 
     fun decrypt(
         message: ByteArray,
         nonce: ByteArray,
         key: ByteArray,
-    ) = decryptLibSodium(message, nonce, key)
-
-    /*
-    fun encryptNative(
-        message: ByteArray,
-        nonce: ByteArray,
-        key: ByteArray,
-    ): ByteArray {
-        val cipher = Cipher.getInstance("ChaCha20")
-        cipher.init(Cipher.ENCRYPT_MODE, FixedKey(key, "ChaCha20"), IvParameterSpec(nonce))
-        return cipher.doFinal(message)
-    }
-
-    fun decryptNative(
-        message: ByteArray,
-        nonce: ByteArray,
-        key: ByteArray,
-    ): ByteArray {
-        val cipher = Cipher.getInstance("ChaCha20")
-        cipher.init(Cipher.DECRYPT_MODE, FixedKey(key, "ChaCha20"), IvParameterSpec(nonce))
-        return cipher.doFinal(message)
-    }
-     */
-
-    fun encryptLibSodium(
-        message: ByteArray,
-        nonce: ByteArray,
-        key: ByteArray,
-    ) = LibSodiumInstance.cryptoStreamChaCha20IetfXor(message, nonce, key)
-
-    fun decryptLibSodium(
-        message: ByteArray,
-        nonce: ByteArray,
-        key: ByteArray,
-    ) = LibSodiumInstance.cryptoStreamChaCha20IetfXor(message, nonce, key)
+    ) = ChaCha20Core.chaCha20Xor(message, key, nonce, counter = 0)
 }
diff --git a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/ChaCha20Core.kt b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/ChaCha20Core.kt
new file mode 100644
index 000000000..2d9abce80
--- /dev/null
+++ b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/ChaCha20Core.kt
@@ -0,0 +1,266 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.quartz.nip44Encryption.crypto
+
+/**
+ * Pure Kotlin implementation of ChaCha20, HChaCha20, and XChaCha20.
+ *
+ * All functions are stateless and thread-safe — they use only local variables
+ * and produce no side effects beyond their return values.
+ *
+ * References:
+ * - RFC 8439: ChaCha20 and Poly1305
+ * - draft-irtf-cfrg-xchacha: XChaCha20 (HChaCha20 + ChaCha20)
+ */
+object ChaCha20Core {
+    // "expand 32-byte k" as little-endian integers
+    private const val SIGMA0 = 0x61707865.toInt()
+    private const val SIGMA1 = 0x3320646e.toInt()
+    private const val SIGMA2 = 0x79622d32.toInt()
+    private const val SIGMA3 = 0x6b206574.toInt()
+
+    /**
+     * ChaCha20 quarter round (RFC 8439 §2.1).
+     * Operates in-place on the 16-word state.
+     */
+    private fun quarterRound(
+        state: IntArray,
+        a: Int,
+        b: Int,
+        c: Int,
+        d: Int,
+    ) {
+        state[a] += state[b]; state[d] = (state[d] xor state[a]).rotateLeft(16)
+        state[c] += state[d]; state[b] = (state[b] xor state[c]).rotateLeft(12)
+        state[a] += state[b]; state[d] = (state[d] xor state[a]).rotateLeft(8)
+        state[c] += state[d]; state[b] = (state[b] xor state[c]).rotateLeft(7)
+    }
+
+    /**
+     * Perform 20 rounds (10 double-rounds) of ChaCha on the state.
+     */
+    private fun chaCha20Rounds(state: IntArray) {
+        repeat(10) {
+            // Column rounds
+            quarterRound(state, 0, 4, 8, 12)
+            quarterRound(state, 1, 5, 9, 13)
+            quarterRound(state, 2, 6, 10, 14)
+            quarterRound(state, 3, 7, 11, 15)
+            // Diagonal rounds
+            quarterRound(state, 0, 5, 10, 15)
+            quarterRound(state, 1, 6, 11, 12)
+            quarterRound(state, 2, 7, 8, 13)
+            quarterRound(state, 3, 4, 9, 14)
+        }
+    }
+
+    /**
+     * Initialize the ChaCha20 state matrix from key, counter, and nonce.
+     * Layout (RFC 8439 §2.3):
+     *   cccccccc  cccccccc  cccccccc  cccccccc
+     *   kkkkkkkk  kkkkkkkk  kkkkkkkk  kkkkkkkk
+     *   kkkkkkkk  kkkkkkkk  kkkkkkkk  kkkkkkkk
+     *   bbbbbbbb  nnnnnnnn  nnnnnnnn  nnnnnnnn
+     */
+    private fun initState(
+        key: ByteArray,
+        counter: Int,
+        nonce: ByteArray,
+    ): IntArray {
+        val state = IntArray(16)
+        state[0] = SIGMA0
+        state[1] = SIGMA1
+        state[2] = SIGMA2
+        state[3] = SIGMA3
+        state[4] = key.littleEndianToInt(0)
+        state[5] = key.littleEndianToInt(4)
+        state[6] = key.littleEndianToInt(8)
+        state[7] = key.littleEndianToInt(12)
+        state[8] = key.littleEndianToInt(16)
+        state[9] = key.littleEndianToInt(20)
+        state[10] = key.littleEndianToInt(24)
+        state[11] = key.littleEndianToInt(28)
+        state[12] = counter
+        state[13] = nonce.littleEndianToInt(0)
+        state[14] = nonce.littleEndianToInt(4)
+        state[15] = nonce.littleEndianToInt(8)
+        return state
+    }
+
+    /**
+     * ChaCha20 block function (RFC 8439 §2.3).
+     * Produces a 64-byte keystream block.
+     *
+     * @param key 32-byte key
+     * @param counter block counter
+     * @param nonce 12-byte nonce (IETF variant)
+     * @return 64-byte keystream block
+     */
+    fun chaCha20Block(
+        key: ByteArray,
+        counter: Int,
+        nonce: ByteArray,
+    ): ByteArray {
+        val initial = initState(key, counter, nonce)
+        val working = initial.copyOf()
+        chaCha20Rounds(working)
+
+        // Add initial state to working state
+        for (i in 0..15) {
+            working[i] += initial[i]
+        }
+
+        // Serialize to little-endian bytes
+        val output = ByteArray(64)
+        for (i in 0..15) {
+            working[i].intToLittleEndian(output, i * 4)
+        }
+        return output
+    }
+
+    /**
+     * ChaCha20 IETF stream cipher XOR (RFC 8439 §2.4).
+     * XORs the message with the ChaCha20 keystream.
+     *
+     * @param message plaintext or ciphertext
+     * @param key 32-byte key
+     * @param nonce 12-byte nonce
+     * @param counter initial block counter (0 for stream cipher, 1 for AEAD)
+     * @return XOR'd output (same length as message)
+     */
+    fun chaCha20Xor(
+        message: ByteArray,
+        key: ByteArray,
+        nonce: ByteArray,
+        counter: Int = 0,
+    ): ByteArray {
+        val output = ByteArray(message.size)
+        val fullBlocks = message.size / 64
+        val remainder = message.size % 64
+
+        for (i in 0 until fullBlocks) {
+            val block = chaCha20Block(key, counter + i, nonce)
+            val offset = i * 64
+            for (j in 0..63) {
+                output[offset + j] = (message[offset + j].toInt() xor block[j].toInt()).toByte()
+            }
+        }
+
+        if (remainder > 0) {
+            val block = chaCha20Block(key, counter + fullBlocks, nonce)
+            val offset = fullBlocks * 64
+            for (j in 0 until remainder) {
+                output[offset + j] = (message[offset + j].toInt() xor block[j].toInt()).toByte()
+            }
+        }
+
+        return output
+    }
+
+    /**
+     * HChaCha20 (draft-irtf-cfrg-xchacha §2.2).
+     * Derives a 32-byte subkey from a 32-byte key and 16-byte input.
+     * Used as the first step of XChaCha20.
+     *
+     * @param key 32-byte key
+     * @param input 16-byte input (first 16 bytes of the 24-byte XChaCha20 nonce)
+     * @return 32-byte subkey
+     */
+    fun hChaCha20(
+        key: ByteArray,
+        input: ByteArray,
+    ): ByteArray {
+        val state = IntArray(16)
+        state[0] = SIGMA0
+        state[1] = SIGMA1
+        state[2] = SIGMA2
+        state[3] = SIGMA3
+        state[4] = key.littleEndianToInt(0)
+        state[5] = key.littleEndianToInt(4)
+        state[6] = key.littleEndianToInt(8)
+        state[7] = key.littleEndianToInt(12)
+        state[8] = key.littleEndianToInt(16)
+        state[9] = key.littleEndianToInt(20)
+        state[10] = key.littleEndianToInt(24)
+        state[11] = key.littleEndianToInt(28)
+        state[12] = input.littleEndianToInt(0)
+        state[13] = input.littleEndianToInt(4)
+        state[14] = input.littleEndianToInt(8)
+        state[15] = input.littleEndianToInt(12)
+
+        chaCha20Rounds(state)
+
+        // Output words 0-3 and 12-15 (skip the key material in 4-11)
+        val output = ByteArray(32)
+        state[0].intToLittleEndian(output, 0)
+        state[1].intToLittleEndian(output, 4)
+        state[2].intToLittleEndian(output, 8)
+        state[3].intToLittleEndian(output, 12)
+        state[12].intToLittleEndian(output, 16)
+        state[13].intToLittleEndian(output, 20)
+        state[14].intToLittleEndian(output, 24)
+        state[15].intToLittleEndian(output, 28)
+        return output
+    }
+
+    /**
+     * XChaCha20 stream cipher XOR (draft-irtf-cfrg-xchacha §2.3).
+     * Uses HChaCha20 to derive a subkey, then applies ChaCha20 with the remaining nonce bytes.
+     *
+     * @param message plaintext or ciphertext
+     * @param nonce 24-byte nonce
+     * @param key 32-byte key
+     * @return XOR'd output (same length as message)
+     */
+    fun xChaCha20Xor(
+        message: ByteArray,
+        nonce: ByteArray,
+        key: ByteArray,
+    ): ByteArray {
+        // Step 1: Derive subkey using first 16 bytes of nonce
+        val subKey = hChaCha20(key, nonce.copyOfRange(0, 16))
+
+        // Step 2: Build 12-byte subnonce: 4 zero bytes + last 8 bytes of nonce
+        val subNonce = ByteArray(12)
+        nonce.copyInto(subNonce, destinationOffset = 4, startIndex = 16, endIndex = 24)
+
+        // Step 3: Encrypt with ChaCha20 using subkey, counter=0
+        return chaCha20Xor(message, subKey, subNonce, counter = 0)
+    }
+}
+
+// --- Little-endian conversion helpers ---
+
+private fun ByteArray.littleEndianToInt(offset: Int): Int =
+    (this[offset].toInt() and 0xFF) or
+        ((this[offset + 1].toInt() and 0xFF) shl 8) or
+        ((this[offset + 2].toInt() and 0xFF) shl 16) or
+        ((this[offset + 3].toInt() and 0xFF) shl 24)
+
+private fun Int.intToLittleEndian(
+    output: ByteArray,
+    offset: Int,
+) {
+    output[offset] = (this and 0xFF).toByte()
+    output[offset + 1] = (this ushr 8 and 0xFF).toByte()
+    output[offset + 2] = (this ushr 16 and 0xFF).toByte()
+    output[offset + 3] = (this ushr 24 and 0xFF).toByte()
+}
diff --git a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/Poly1305.kt b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/Poly1305.kt
new file mode 100644
index 000000000..f5ff591be
--- /dev/null
+++ b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/Poly1305.kt
@@ -0,0 +1,202 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.quartz.nip44Encryption.crypto
+
+/**
+ * Pure Kotlin implementation of Poly1305 one-time authenticator (RFC 8439 §2.5).
+ *
+ * Uses 130-bit arithmetic with 5 limbs of 26 bits each, following the approach
+ * from D.J. Bernstein's reference implementation. All functions are stateless
+ * and thread-safe.
+ *
+ * The 32-byte key is split into:
+ * - r (first 16 bytes): clamped per spec, used as the multiplier
+ * - s (last 16 bytes): added at the end
+ */
+object Poly1305 {
+    /**
+     * Compute a 16-byte Poly1305 MAC.
+     *
+     * @param message the data to authenticate
+     * @param key 32-byte one-time key (r || s)
+     * @return 16-byte authentication tag
+     */
+    fun mac(
+        message: ByteArray,
+        key: ByteArray,
+    ): ByteArray {
+        // Parse and clamp r from first 16 bytes of key
+        val r0 = (key.leToLong(0)) and 0x3ffffff
+        val r1 = (key.leToLong(3) ushr 2) and 0x3ffff03
+        val r2 = (key.leToLong(6) ushr 4) and 0x3ffc0ff
+        val r3 = (key.leToLong(9) ushr 6) and 0x3f03fff
+        val r4 = (key.leToLong(12) ushr 8) and 0x00fffff
+
+        // Precompute 5*r for the reduction step
+        val s1 = r1 * 5
+        val s2 = r2 * 5
+        val s3 = r3 * 5
+        val s4 = r4 * 5
+
+        // Accumulator: 5 limbs of 26 bits
+        var h0 = 0L
+        var h1 = 0L
+        var h2 = 0L
+        var h3 = 0L
+        var h4 = 0L
+
+        val fullBlocks = message.size / 16
+        val remainder = message.size % 16
+
+        // Process full 16-byte blocks
+        for (i in 0 until fullBlocks) {
+            val offset = i * 16
+            h0 += (message.leToLong(offset)) and 0x3ffffff
+            h1 += (message.leToLong(offset + 3) ushr 2) and 0x3ffffff
+            h2 += (message.leToLong(offset + 6) ushr 4) and 0x3ffffff
+            h3 += (message.leToLong(offset + 9) ushr 6) and 0x3ffffff
+            h4 += (message.leToLong(offset + 12) ushr 8) or (1L shl 24) // hibit = 1
+
+            // Multiply and reduce
+            val d0 = h0 * r0 + h1 * s4 + h2 * s3 + h3 * s2 + h4 * s1
+            val d1 = h0 * r1 + h1 * r0 + h2 * s4 + h3 * s3 + h4 * s2
+            val d2 = h0 * r2 + h1 * r1 + h2 * r0 + h3 * s4 + h4 * s3
+            val d3 = h0 * r3 + h1 * r2 + h2 * r1 + h3 * r0 + h4 * s4
+            val d4 = h0 * r4 + h1 * r3 + h2 * r2 + h3 * r1 + h4 * r0
+
+            // Partial reduction mod 2^130 - 5
+            var c: Long
+            c = d0 ushr 26; h0 = d0 and 0x3ffffff; h1 = d1 + c
+            c = h1 ushr 26; h1 = h1 and 0x3ffffff; h2 = d2 + c
+            c = h2 ushr 26; h2 = h2 and 0x3ffffff; h3 = d3 + c
+            c = h3 ushr 26; h3 = h3 and 0x3ffffff; h4 = d4 + c
+            c = h4 ushr 26; h4 = h4 and 0x3ffffff; h0 += c * 5
+            c = h0 ushr 26; h0 = h0 and 0x3ffffff; h1 += c
+        }
+
+        // Process remaining bytes (if any)
+        if (remainder > 0) {
+            val block = ByteArray(17)
+            message.copyInto(block, 0, fullBlocks * 16, message.size)
+            block[remainder] = 1 // pad with 0x01
+
+            h0 += (block.leToLong(0)) and 0x3ffffff
+            h1 += (block.leToLong(3) ushr 2) and 0x3ffffff
+            h2 += (block.leToLong(6) ushr 4) and 0x3ffffff
+            h3 += (block.leToLong(9) ushr 6) and 0x3ffffff
+            h4 += (block.leToLong(12) ushr 8)
+
+            val d0 = h0 * r0 + h1 * s4 + h2 * s3 + h3 * s2 + h4 * s1
+            val d1 = h0 * r1 + h1 * r0 + h2 * s4 + h3 * s3 + h4 * s2
+            val d2 = h0 * r2 + h1 * r1 + h2 * r0 + h3 * s4 + h4 * s3
+            val d3 = h0 * r3 + h1 * r2 + h2 * r1 + h3 * r0 + h4 * s4
+            val d4 = h0 * r4 + h1 * r3 + h2 * r2 + h3 * r1 + h4 * r0
+
+            var c: Long
+            c = d0 ushr 26; h0 = d0 and 0x3ffffff; h1 = d1 + c
+            c = h1 ushr 26; h1 = h1 and 0x3ffffff; h2 = d2 + c
+            c = h2 ushr 26; h2 = h2 and 0x3ffffff; h3 = d3 + c
+            c = h3 ushr 26; h3 = h3 and 0x3ffffff; h4 = d4 + c
+            c = h4 ushr 26; h4 = h4 and 0x3ffffff; h0 += c * 5
+            c = h0 ushr 26; h0 = h0 and 0x3ffffff; h1 += c
+        }
+
+        // Final reduction: fully carry and reduce mod 2^130 - 5
+        var c: Long
+        c = h1 ushr 26; h1 = h1 and 0x3ffffff; h2 += c
+        c = h2 ushr 26; h2 = h2 and 0x3ffffff; h3 += c
+        c = h3 ushr 26; h3 = h3 and 0x3ffffff; h4 += c
+        c = h4 ushr 26; h4 = h4 and 0x3ffffff; h0 += c * 5
+        c = h0 ushr 26; h0 = h0 and 0x3ffffff; h1 += c
+
+        // Compute h + -(2^130 - 5) = h - 2^130 + 5
+        var g0 = h0 + 5; c = g0 ushr 26; g0 = g0 and 0x3ffffff
+        var g1 = h1 + c; c = g1 ushr 26; g1 = g1 and 0x3ffffff
+        var g2 = h2 + c; c = g2 ushr 26; g2 = g2 and 0x3ffffff
+        var g3 = h3 + c; c = g3 ushr 26; g3 = g3 and 0x3ffffff
+        var g4 = h4 + c - (1L shl 26)
+
+        // Select h if g4 is negative (bit 63 set), else select g
+        val mask = (g4 ushr 63) - 1 // 0 if h, all-ones if g
+        g0 = g0 and mask
+        g1 = g1 and mask
+        g2 = g2 and mask
+        g3 = g3 and mask
+        g4 = g4 and mask
+        val nmask = mask.inv()
+        h0 = (h0 and nmask) or g0
+        h1 = (h1 and nmask) or g1
+        h2 = (h2 and nmask) or g2
+        h3 = (h3 and nmask) or g3
+        h4 = (h4 and nmask) or g4
+
+        // Assemble h into 4 32-bit words
+        var f0 = ((h0) or (h1 shl 26)) and 0xffffffffL
+        var f1 = ((h1 ushr 6) or (h2 shl 20)) and 0xffffffffL
+        var f2 = ((h2 ushr 12) or (h3 shl 14)) and 0xffffffffL
+        var f3 = ((h3 ushr 18) or (h4 shl 8)) and 0xffffffffL
+
+        // Add s (second half of the key)
+        val s0 = key.leToUInt(16)
+        val s1Long = key.leToUInt(20)
+        val s2Long = key.leToUInt(24)
+        val s3Long = key.leToUInt(28)
+
+        f0 += s0; c = f0 ushr 32
+        f1 += s1Long + c; c = f1 ushr 32
+        f2 += s2Long + c; c = f2 ushr 32
+        f3 += s3Long + c
+
+        // Output as little-endian bytes
+        val tag = ByteArray(16)
+        tag[0] = (f0).toByte()
+        tag[1] = (f0 ushr 8).toByte()
+        tag[2] = (f0 ushr 16).toByte()
+        tag[3] = (f0 ushr 24).toByte()
+        tag[4] = (f1).toByte()
+        tag[5] = (f1 ushr 8).toByte()
+        tag[6] = (f1 ushr 16).toByte()
+        tag[7] = (f1 ushr 24).toByte()
+        tag[8] = (f2).toByte()
+        tag[9] = (f2 ushr 8).toByte()
+        tag[10] = (f2 ushr 16).toByte()
+        tag[11] = (f2 ushr 24).toByte()
+        tag[12] = (f3).toByte()
+        tag[13] = (f3 ushr 8).toByte()
+        tag[14] = (f3 ushr 16).toByte()
+        tag[15] = (f3 ushr 24).toByte()
+        return tag
+    }
+}
+
+/** Read 4 bytes as unsigned little-endian Long starting at [offset]. */
+private fun ByteArray.leToUInt(offset: Int): Long =
+    (this[offset].toLong() and 0xFF) or
+        ((this[offset + 1].toLong() and 0xFF) shl 8) or
+        ((this[offset + 2].toLong() and 0xFF) shl 16) or
+        ((this[offset + 3].toLong() and 0xFF) shl 24)
+
+/** Read 4 bytes as unsigned little-endian Long starting at [offset]. Used for Poly1305 limb loading. */
+private fun ByteArray.leToLong(offset: Int): Long =
+    (this[offset].toLong() and 0xFF) or
+        ((this[offset + 1].toLong() and 0xFF) shl 8) or
+        ((this[offset + 2].toLong() and 0xFF) shl 16) or
+        ((this[offset + 3].toLong() and 0xFF) shl 24)
diff --git a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/XChaCha20Poly1305.kt b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/XChaCha20Poly1305.kt
new file mode 100644
index 000000000..c3835ecc7
--- /dev/null
+++ b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/XChaCha20Poly1305.kt
@@ -0,0 +1,168 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.quartz.nip44Encryption.crypto
+
+/**
+ * Pure Kotlin implementation of XChaCha20-Poly1305 AEAD (RFC 8439 §2.8 + XChaCha20 draft).
+ *
+ * All functions are stateless and thread-safe.
+ *
+ * Construction:
+ * 1. Derive subkey via HChaCha20(key, nonce[0..15])
+ * 2. Build 12-byte subnonce: 0x00000000 || nonce[16..23]
+ * 3. Generate Poly1305 OTK from ChaCha20 block 0
+ * 4. Encrypt with ChaCha20 starting at counter 1
+ * 5. Compute Poly1305 tag over: pad16(ad) || pad16(ciphertext) || len(ad) || len(ct)
+ */
+object XChaCha20Poly1305 {
+    private const val TAG_SIZE = 16
+
+    /**
+     * AEAD encrypt.
+     *
+     * @param plaintext message to encrypt
+     * @param ad associated data (authenticated but not encrypted)
+     * @param nonce 24-byte nonce
+     * @param key 32-byte key
+     * @return ciphertext || 16-byte tag
+     */
+    fun encrypt(
+        plaintext: ByteArray,
+        ad: ByteArray,
+        nonce: ByteArray,
+        key: ByteArray,
+    ): ByteArray {
+        // Step 1-2: Derive subkey and subnonce
+        val subKey = ChaCha20Core.hChaCha20(key, nonce.copyOfRange(0, 16))
+        val subNonce = ByteArray(12)
+        nonce.copyInto(subNonce, destinationOffset = 4, startIndex = 16, endIndex = 24)
+
+        // Step 3: Generate Poly1305 one-time key from block 0
+        val polyKey = ChaCha20Core.chaCha20Block(subKey, 0, subNonce).copyOfRange(0, 32)
+
+        // Step 4: Encrypt plaintext with counter starting at 1
+        val ciphertext = ChaCha20Core.chaCha20Xor(plaintext, subKey, subNonce, counter = 1)
+
+        // Step 5: Compute tag
+        val tag = computeTag(polyKey, ad, ciphertext)
+
+        // Step 6: Return ciphertext || tag
+        return ciphertext + tag
+    }
+
+    /**
+     * AEAD decrypt.
+     *
+     * @param ciphertextWithTag ciphertext || 16-byte tag
+     * @param ad associated data
+     * @param nonce 24-byte nonce
+     * @param key 32-byte key
+     * @return plaintext, or throws on authentication failure
+     */
+    fun decrypt(
+        ciphertextWithTag: ByteArray,
+        ad: ByteArray,
+        nonce: ByteArray,
+        key: ByteArray,
+    ): ByteArray {
+        require(ciphertextWithTag.size >= TAG_SIZE) { "Ciphertext too short" }
+
+        val ctLen = ciphertextWithTag.size - TAG_SIZE
+        val ciphertext = ciphertextWithTag.copyOfRange(0, ctLen)
+        val receivedTag = ciphertextWithTag.copyOfRange(ctLen, ciphertextWithTag.size)
+
+        // Step 1-2: Derive subkey and subnonce
+        val subKey = ChaCha20Core.hChaCha20(key, nonce.copyOfRange(0, 16))
+        val subNonce = ByteArray(12)
+        nonce.copyInto(subNonce, destinationOffset = 4, startIndex = 16, endIndex = 24)
+
+        // Step 3: Generate Poly1305 one-time key
+        val polyKey = ChaCha20Core.chaCha20Block(subKey, 0, subNonce).copyOfRange(0, 32)
+
+        // Step 4: Verify tag
+        val expectedTag = computeTag(polyKey, ad, ciphertext)
+        check(constantTimeEquals(receivedTag, expectedTag)) { "Authentication failed" }
+
+        // Step 5: Decrypt
+        return ChaCha20Core.chaCha20Xor(ciphertext, subKey, subNonce, counter = 1)
+    }
+
+    /**
+     * Compute Poly1305 tag over the AEAD construction:
+     * pad16(ad) || pad16(ciphertext) || len(ad) as 8-byte LE || len(ct) as 8-byte LE
+     */
+    private fun computeTag(
+        polyKey: ByteArray,
+        ad: ByteArray,
+        ciphertext: ByteArray,
+    ): ByteArray {
+        val adPadLen = if (ad.size % 16 == 0) 0 else 16 - (ad.size % 16)
+        val ctPadLen = if (ciphertext.size % 16 == 0) 0 else 16 - (ciphertext.size % 16)
+
+        val macData = ByteArray(ad.size + adPadLen + ciphertext.size + ctPadLen + 16)
+        var offset = 0
+
+        // pad16(ad)
+        ad.copyInto(macData, offset)
+        offset += ad.size + adPadLen
+
+        // pad16(ciphertext)
+        ciphertext.copyInto(macData, offset)
+        offset += ciphertext.size + ctPadLen
+
+        // len(ad) as 8-byte little-endian
+        longToLittleEndian(ad.size.toLong(), macData, offset)
+        offset += 8
+
+        // len(ciphertext) as 8-byte little-endian
+        longToLittleEndian(ciphertext.size.toLong(), macData, offset)
+
+        return Poly1305.mac(macData, polyKey)
+    }
+
+    /** Constant-time comparison to prevent timing attacks. */
+    private fun constantTimeEquals(
+        a: ByteArray,
+        b: ByteArray,
+    ): Boolean {
+        if (a.size != b.size) return false
+        var result = 0
+        for (i in a.indices) {
+            result = result or (a[i].toInt() xor b[i].toInt())
+        }
+        return result == 0
+    }
+
+    private fun longToLittleEndian(
+        value: Long,
+        output: ByteArray,
+        offset: Int,
+    ) {
+        output[offset] = (value and 0xFF).toByte()
+        output[offset + 1] = (value ushr 8 and 0xFF).toByte()
+        output[offset + 2] = (value ushr 16 and 0xFF).toByte()
+        output[offset + 3] = (value ushr 24 and 0xFF).toByte()
+        output[offset + 4] = (value ushr 32 and 0xFF).toByte()
+        output[offset + 5] = (value ushr 40 and 0xFF).toByte()
+        output[offset + 6] = (value ushr 48 and 0xFF).toByte()
+        output[offset + 7] = (value ushr 56 and 0xFF).toByte()
+    }
+}
diff --git a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/utils/LibSodiumInstance.kt b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/utils/LibSodiumInstance.kt
index 1ebf25086..2f5b0225c 100644
--- a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/utils/LibSodiumInstance.kt
+++ b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/utils/LibSodiumInstance.kt
@@ -20,7 +20,14 @@
  */
 package com.vitorpamplona.quartz.utils
 
-expect object LibSodiumInstance {
+import com.vitorpamplona.quartz.nip44Encryption.crypto.ChaCha20Core
+import com.vitorpamplona.quartz.nip44Encryption.crypto.XChaCha20Poly1305
+
+/**
+ * Pure Kotlin replacement for LazySodium/libsodium.
+ * All functions are stateless and thread-safe.
+ */
+object LibSodiumInstance {
     fun cryptoAeadXChaCha20Poly1305IetfDecrypt(
         message: ByteArray,
         nSec: ByteArray,
@@ -28,7 +35,14 @@ expect object LibSodiumInstance {
         ad: ByteArray,
         nPub: ByteArray,
         k: ByteArray,
-    ): Boolean
+    ): Boolean =
+        try {
+            val plaintext = XChaCha20Poly1305.decrypt(ciphertext, ad, nPub, k)
+            plaintext.copyInto(message)
+            true
+        } catch (_: Exception) {
+            false
+        }
 
     fun cryptoAeadXChaCha20Poly1305IetfEncrypt(
         ciphertext: ByteArray,
@@ -37,18 +51,24 @@ expect object LibSodiumInstance {
         nSec: ByteArray,
         nPub: ByteArray,
         k: ByteArray,
-    ): Boolean
+    ): Boolean =
+        try {
+            val result = XChaCha20Poly1305.encrypt(message, ad, nPub, k)
+            result.copyInto(ciphertext)
+            true
+        } catch (_: Exception) {
+            false
+        }
 
     fun cryptoStreamChaCha20IetfXor(
         message: ByteArray,
         nonce: ByteArray?,
         key: ByteArray?,
-    ): ByteArray
+    ): ByteArray = ChaCha20Core.chaCha20Xor(message, key!!, nonce!!, counter = 0)
 
-    // This function wasn't available in the bindings library. I had to move them here from C
     fun cryptoStreamXChaCha20Xor(
         messageBytes: ByteArray,
         nonce: ByteArray,
         key: ByteArray,
-    ): ByteArray
+    ): ByteArray = ChaCha20Core.xChaCha20Xor(messageBytes, nonce, key)
 }
diff --git a/quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/ChaCha20CoreTest.kt b/quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/ChaCha20CoreTest.kt
new file mode 100644
index 000000000..af6a1a597
--- /dev/null
+++ b/quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/ChaCha20CoreTest.kt
@@ -0,0 +1,253 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.quartz.nip44Encryption.crypto
+
+import kotlin.test.Test
+import kotlin.test.assertContentEquals
+import kotlin.test.assertEquals
+import kotlin.test.assertFailsWith
+
+/**
+ * Test vectors from RFC 8439, XChaCha20 draft (draft-irtf-cfrg-xchacha-03),
+ * and libsodium test suite.
+ */
+class ChaCha20CoreTest {
+    private fun hex(s: String): ByteArray =
+        s.replace(" ", "").chunked(2).map { it.toInt(16).toByte() }.toByteArray()
+
+    private fun ByteArray.toHex(): String = joinToString("") { "%02x".format(it) }
+
+    // ===== RFC 8439 §2.3.2: ChaCha20 Block Function Test Vector =====
+    @Test
+    fun testChaCha20Block_RFC8439() {
+        val key = hex("000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f")
+        val nonce = hex("000000090000004a00000000")
+        val counter = 1
+
+        val block = ChaCha20Core.chaCha20Block(key, counter, nonce)
+
+        val expected =
+            hex(
+                "10f1e7e4d13b5915500fdd1fa32071c4" +
+                    "c7d1f4c733c068030422aa9ac3d46c4e" +
+                    "d2826446079faa0914c2d705d98b02a2" +
+                    "b5129cd1de164eb9cbd083e8a2503c4e",
+            )
+        assertContentEquals(expected, block)
+    }
+
+    // ===== RFC 8439 §2.4.2: ChaCha20 Encryption Test Vector =====
+    @Test
+    fun testChaCha20Encrypt_RFC8439() {
+        val key = hex("000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f")
+        val nonce = hex("000000000000004a00000000")
+        val counter = 1
+        val plaintext =
+            "Ladies and Gentlemen of the class of '99: If I could offer you only one tip for the future, sunscreen would be it."
+                .encodeToByteArray()
+
+        val ciphertext = ChaCha20Core.chaCha20Xor(plaintext, key, nonce, counter)
+
+        val expected =
+            hex(
+                "6e2e359a2568f98041ba0728dd0d6981" +
+                    "e97e7aec1d4360c20a27afccfd9fae0b" +
+                    "f91b65c5524733ab8f593dabcd62b357" +
+                    "1639d624e65152ab8f530c359f0861d8" +
+                    "07ca0dbf500d6a6156a38e088a22b65e" +
+                    "52bc514d16ccf806818ce91ab7793736" +
+                    "5af90bbf74a35be6b40b8eedf2785e42" +
+                    "874d",
+            )
+        assertContentEquals(expected, ciphertext)
+    }
+
+    // ===== RFC 8439 §2.5.2: Poly1305 Test Vector =====
+    @Test
+    fun testPoly1305_RFC8439() {
+        val key = hex("85d6be7857556d337f4452fe42d506a80103808afb0db2fd4abff6af4149f51b")
+        val message =
+            "Cryptographic Forum Research Group".encodeToByteArray()
+
+        val tag = Poly1305.mac(message, key)
+
+        val expected = hex("a8061dc1305136c6c22b8baf0c0127a9")
+        assertContentEquals(expected, tag)
+    }
+
+    // ===== RFC 8439 §2.8.2: AEAD ChaCha20-Poly1305 Test Vector =====
+    // Adapted for XChaCha20 via the XChaCha20 draft test vector
+    @Test
+    fun testPoly1305KeyGeneration_RFC8439() {
+        // RFC 8439 §2.6.2 Poly1305 Key Generation
+        val key = hex("808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9f")
+        val nonce = hex("000000000001020304050607")
+
+        val block = ChaCha20Core.chaCha20Block(key, 0, nonce)
+        val polyKey = block.copyOfRange(0, 32)
+
+        val expected = hex("8ad5a08b905f81cc815040274ab29471a833b637e3fd0da508dbb8e2fdd1a646")
+        assertContentEquals(expected, polyKey)
+    }
+
+    // ===== XChaCha20 draft §2.2.1: HChaCha20 Test Vector =====
+    @Test
+    fun testHChaCha20_Draft() {
+        val key = hex("000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f")
+        val input = hex("000000090000004a0000000031415927")
+
+        val subKey = ChaCha20Core.hChaCha20(key, input)
+
+        val expected = hex("82413b4227b27bfed30e42508a877d73a0f9e4d58a74a853c12ec41326d3ecdc")
+        assertContentEquals(expected, subKey)
+    }
+
+    // ===== XChaCha20 draft §A.3.1: XChaCha20-Poly1305 AEAD Test Vector =====
+    @Test
+    fun testXChaCha20Poly1305Encrypt_Draft() {
+        val key = hex("808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9f")
+        val nonce = hex("404142434445464748494a4b4c4d4e4f5051525354555657")
+        val ad = hex("50515253c0c1c2c3c4c5c6c7")
+        val plaintext =
+            "Ladies and Gentlemen of the class of '99: If I could offer you only one tip for the future, sunscreen would be it."
+                .encodeToByteArray()
+
+        val result = XChaCha20Poly1305.encrypt(plaintext, ad, nonce, key)
+
+        // Ciphertext portion
+        val expectedCiphertext =
+            hex(
+                "bd6d179d3e83d43b9576579493c0e939572a1700252bfaccbed2902c21396cbb" +
+                    "731c7f1b0b4aa6440bf3a82f4eda7e39ae64c6708c54c216cb96b72e1213b452" +
+                    "2f8c9ba40db5d945b11b69b982c1bb9e3f3fac2bc369488f76b2383565d3fff9" +
+                    "21f9664c97637da9768812f615c68b13b52e",
+            )
+        // Tag portion
+        val expectedTag = hex("c0875924c1c7987947deafd8780acf49")
+
+        val ciphertext = result.copyOfRange(0, result.size - 16)
+        val tag = result.copyOfRange(result.size - 16, result.size)
+
+        assertContentEquals(expectedCiphertext, ciphertext)
+        assertContentEquals(expectedTag, tag)
+    }
+
+    @Test
+    fun testXChaCha20Poly1305Decrypt_Draft() {
+        val key = hex("808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9f")
+        val nonce = hex("404142434445464748494a4b4c4d4e4f5051525354555657")
+        val ad = hex("50515253c0c1c2c3c4c5c6c7")
+        val ciphertextWithTag =
+            hex(
+                "bd6d179d3e83d43b9576579493c0e939572a1700252bfaccbed2902c21396cbb" +
+                    "731c7f1b0b4aa6440bf3a82f4eda7e39ae64c6708c54c216cb96b72e1213b452" +
+                    "2f8c9ba40db5d945b11b69b982c1bb9e3f3fac2bc369488f76b2383565d3fff9" +
+                    "21f9664c97637da9768812f615c68b13b52e" +
+                    "c0875924c1c7987947deafd8780acf49",
+            )
+
+        val plaintext = XChaCha20Poly1305.decrypt(ciphertextWithTag, ad, nonce, key)
+
+        val expected =
+            "Ladies and Gentlemen of the class of '99: If I could offer you only one tip for the future, sunscreen would be it."
+        assertEquals(expected, plaintext.decodeToString())
+    }
+
+    @Test
+    fun testXChaCha20Poly1305_TamperedCiphertext() {
+        val key = hex("808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9f")
+        val nonce = hex("404142434445464748494a4b4c4d4e4f5051525354555657")
+        val ad = hex("50515253c0c1c2c3c4c5c6c7")
+        val plaintext = "Test message".encodeToByteArray()
+
+        val encrypted = XChaCha20Poly1305.encrypt(plaintext, ad, nonce, key)
+        // Flip a bit in the ciphertext
+        encrypted[0] = (encrypted[0].toInt() xor 1).toByte()
+
+        assertFailsWith<IllegalStateException> {
+            XChaCha20Poly1305.decrypt(encrypted, ad, nonce, key)
+        }
+    }
+
+    @Test
+    fun testXChaCha20Poly1305_RoundTrip() {
+        val key = hex("000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f")
+        val nonce = hex("000102030405060708090a0b0c0d0e0f1011121314151617")
+        val ad = hex("feedfacedeadbeef")
+        val plaintext = "Hello, Nostr! This is a round-trip test.".encodeToByteArray()
+
+        val encrypted = XChaCha20Poly1305.encrypt(plaintext, ad, nonce, key)
+        val decrypted = XChaCha20Poly1305.decrypt(encrypted, ad, nonce, key)
+
+        assertContentEquals(plaintext, decrypted)
+    }
+
+    @Test
+    fun testXChaCha20Poly1305_EmptyPlaintext() {
+        val key = hex("000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f")
+        val nonce = hex("000102030405060708090a0b0c0d0e0f1011121314151617")
+        val ad = hex("feedface")
+        val plaintext = ByteArray(0)
+
+        val encrypted = XChaCha20Poly1305.encrypt(plaintext, ad, nonce, key)
+        assertEquals(16, encrypted.size) // Just the tag
+        val decrypted = XChaCha20Poly1305.decrypt(encrypted, ad, nonce, key)
+        assertContentEquals(plaintext, decrypted)
+    }
+
+    @Test
+    fun testXChaCha20Poly1305_EmptyAD() {
+        val key = hex("000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f")
+        val nonce = hex("000102030405060708090a0b0c0d0e0f1011121314151617")
+        val ad = ByteArray(0)
+        val plaintext = "No additional data".encodeToByteArray()
+
+        val encrypted = XChaCha20Poly1305.encrypt(plaintext, ad, nonce, key)
+        val decrypted = XChaCha20Poly1305.decrypt(encrypted, ad, nonce, key)
+        assertContentEquals(plaintext, decrypted)
+    }
+
+    // ===== ChaCha20 stream cipher (counter=0) for NIP-44v2 compatibility =====
+    @Test
+    fun testChaCha20Xor_SymmetricEncryptDecrypt() {
+        val key = hex("000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f")
+        val nonce = hex("000000090000004a00000000")
+        val plaintext = "Symmetric cipher test".encodeToByteArray()
+
+        val encrypted = ChaCha20Core.chaCha20Xor(plaintext, key, nonce, counter = 0)
+        val decrypted = ChaCha20Core.chaCha20Xor(encrypted, key, nonce, counter = 0)
+
+        assertContentEquals(plaintext, decrypted)
+    }
+
+    // ===== XChaCha20 stream cipher symmetry =====
+    @Test
+    fun testXChaCha20Xor_SymmetricEncryptDecrypt() {
+        val key = hex("000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f")
+        val nonce = hex("000102030405060708090a0b0c0d0e0f1011121314151617")
+        val plaintext = "XChaCha20 symmetric test".encodeToByteArray()
+
+        val encrypted = ChaCha20Core.xChaCha20Xor(plaintext, nonce, key)
+        val decrypted = ChaCha20Core.xChaCha20Xor(encrypted, nonce, key)
+
+        assertContentEquals(plaintext, decrypted)
+    }
+}
diff --git a/quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/XChaCha20Test.kt b/quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/XChaCha20Test.kt
new file mode 100644
index 000000000..e6fa13c17
--- /dev/null
+++ b/quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip44Encryption/crypto/XChaCha20Test.kt
@@ -0,0 +1,110 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.quartz.nip44Encryption.crypto
+
+import kotlin.test.Test
+import kotlin.test.assertContentEquals
+
+/** Test vectors from libsodium xchacha20.c */
+class XChaCha20Test {
+    private fun hex(s: String): ByteArray =
+        s.chunked(2).map { it.toInt(16).toByte() }.toByteArray()
+
+    // HChaCha20 test vectors from libsodium
+    data class HChaCha20TV(val key: String, val input: String, val expected: String)
+
+    private val hChaCha20Vectors = listOf(
+        HChaCha20TV(
+            "24f11cce8a1b3d61e441561a696c1c1b7e173d084fd4812425435a8896a013dc",
+            "d9660c5900ae19ddad28d6e06e45fe5e",
+            "5966b3eec3bff1189f831f06afe4d4e3be97fa9235ec8c20d08acfbbb4e851e3",
+        ),
+        HChaCha20TV(
+            "80a5f6272031e18bb9bcd84f3385da65e7731b7039f13f5e3d475364cd4d42f7",
+            "c0eccc384b44c88e92c57eb2d5ca4dfa",
+            "6ed11741f724009a640a44fce7320954c46e18e0d7ae063bdbc8d7cf372709df",
+        ),
+        HChaCha20TV(
+            "cb1fc686c0eec11a89438b6f4013bf110e7171dace3297f3a657a309b3199629",
+            "fcd49b93e5f8f299227e64d40dc864a3",
+            "84b7e96937a1a0a406bb7162eeaad34308d49de60fd2f7ec9dc6a79cbab2ca34",
+        ),
+        HChaCha20TV(
+            "6640f4d80af5496ca1bc2cfff1fefbe99638dbceaabd7d0ade118999d45f053d",
+            "31f59ceeeafdbfe8cae7914caeba90d6",
+            "9af4697d2f5574a44834a2c2ae1a0505af9f5d869dbe381a994a18eb374c36a0",
+        ),
+        HChaCha20TV(
+            "0693ff36d971225a44ac92c092c60b399e672e4cc5aafd5e31426f123787ac27",
+            "3a6293da061da405db45be1731d5fc4d",
+            "f87b38609142c01095bfc425573bb3c698f9ae866b7e4216840b9c4caf3b0865",
+        ),
+    )
+
+    @Test
+    fun testHChaCha20_LibsodiumVectors() {
+        for ((i, tv) in hChaCha20Vectors.withIndex()) {
+            val result = ChaCha20Core.hChaCha20(hex(tv.key), hex(tv.input))
+            assertContentEquals(hex(tv.expected), result, "HChaCha20 vector $i failed")
+        }
+    }
+
+    // XChaCha20 stream test vectors from libsodium
+    data class XChaCha20TV(val key: String, val nonce: String, val expected: String)
+
+    private val xChaCha20Vectors = listOf(
+        XChaCha20TV(
+            "79c99798ac67300bbb2704c95c341e3245f3dcb21761b98e52ff45b24f304fc4",
+            "b33ffd3096479bcfbc9aee49417688a0a2554f8d95389419",
+            "c6e9758160083ac604ef90e712ce6e75d7797590744e0cf060f013739c",
+        ),
+        XChaCha20TV(
+            "ddf7784fee099612c40700862189d0397fcc4cc4b3cc02b5456b3a97d1186173",
+            "a9a04491e7bf00c3ca91ac7c2d38a777d88993a7047dfcc4",
+            "2f289d371f6f0abc3cb60d11d9b7b29adf6bc5ad843e8493e928448d",
+        ),
+        XChaCha20TV(
+            "3d12800e7b014e88d68a73f0a95b04b435719936feba60473f02a9e61ae60682",
+            "56bed2599eac99fb27ebf4ffcb770a64772dec4d5849ea2d",
+            "a2c3c1406f33c054a92760a8e0666b84f84fa3a618f0",
+        ),
+        XChaCha20TV(
+            "eadc0e27f77113b5241f8ca9d6f9a5e7f09eee68d8a5cf30700563bf01060b4e",
+            "a171a4ef3fde7c4794c5b86170dc5a099b478f1b852f7b64",
+            "23839f61795c3cdbcee2c749a92543baeeea3cbb721402aa42e6cae140447575f2916c5d71108e3b13357eaf86f060cb",
+        ),
+        XChaCha20TV(
+            "91319c9545c7c804ba6b712e22294c386fe31c4ff3d278827637b959d3dbaab2",
+            "410e854b2a911f174aaf1a56540fc3855851f41c65967a4e",
+            "cbe7d24177119b7fdfa8b06ee04dade4256ba7d35ffda6b89f014e479faef6",
+        ),
+    )
+
+    @Test
+    fun testXChaCha20Xor_LibsodiumVectors() {
+        for ((i, tv) in xChaCha20Vectors.withIndex()) {
+            // XOR zeros with keystream to get the expected keystream output
+            val zeros = ByteArray(hex(tv.expected).size)
+            val result = ChaCha20Core.xChaCha20Xor(zeros, hex(tv.nonce), hex(tv.key))
+            assertContentEquals(hex(tv.expected), result, "XChaCha20 vector $i failed")
+        }
+    }
+}
diff --git a/quartz/src/iosMain/kotlin/com/vitorpamplona/quartz/utils/LibSodiumInstance.ios.kt b/quartz/src/iosMain/kotlin/com/vitorpamplona/quartz/utils/LibSodiumInstance.ios.kt
deleted file mode 100644
index 3b56e181b..000000000
--- a/quartz/src/iosMain/kotlin/com/vitorpamplona/quartz/utils/LibSodiumInstance.ios.kt
+++ /dev/null
@@ -1,130 +0,0 @@
-/*
- * Copyright (c) 2025 Vitor Pamplona
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy of
- * this software and associated documentation files (the "Software"), to deal in
- * the Software without restriction, including without limitation the rights to use,
- * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
- * Software, and to permit persons to whom the Software is furnished to do so,
- * subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in all
- * copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
- * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
- * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
- * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
- * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
- */
-package com.vitorpamplona.quartz.utils
-
-import kotlinx.cinterop.CValuesRef
-import kotlinx.cinterop.ExperimentalForeignApi
-import kotlinx.cinterop.UByteVar
-import kotlinx.cinterop.refTo
-import kotlin.experimental.ExperimentalNativeApi
-
-actual object LibSodiumInstance {
-    @OptIn(ExperimentalForeignApi::class)
-    actual fun cryptoAeadXChaCha20Poly1305IetfDecrypt(
-        message: ByteArray,
-        nSec: ByteArray,
-        ciphertext: ByteArray,
-        ad: ByteArray,
-        nPub: ByteArray,
-        k: ByteArray,
-    ): Boolean {
-        val returnCode =
-            Clibsodium.crypto_aead_xchacha20poly1305_ietf_decrypt(
-                m = message.uRefTo(0),
-                mlen_p = ulongArrayOf(message.size.toULong()).refTo(0),
-                nsec = nSec.uRefTo(0),
-                c = ciphertext.uRefTo(0),
-                clen = ciphertext.size.toULong(),
-                ad = ad.uRefTo(0),
-                adlen = ad.size.toULong(),
-                npub = nPub.uRefTo(0),
-                k = k.uRefTo(0),
-            )
-        return returnCode == 0
-    }
-
-    @OptIn(ExperimentalForeignApi::class)
-    actual fun cryptoAeadXChaCha20Poly1305IetfEncrypt(
-        ciphertext: ByteArray,
-        message: ByteArray,
-        ad: ByteArray,
-        nSec: ByteArray,
-        nPub: ByteArray,
-        k: ByteArray,
-    ): Boolean {
-        val retCode =
-            Clibsodium.crypto_aead_xchacha20poly1305_ietf_encrypt(
-                c = ciphertext.uRefTo(0),
-                clen_p = ulongArrayOf(ciphertext.size.toULong()).refTo(0),
-                m = message.uRefTo(0),
-                mlen = message.size.toULong(),
-                ad = ad.uRefTo(0),
-                adlen = ad.size.toULong(),
-                nsec = nSec.uRefTo(0),
-                npub = nPub.uRefTo(0),
-                k = k.uRefTo(0),
-            )
-
-        return retCode == 0
-    }
-
-    @OptIn(ExperimentalForeignApi::class)
-    actual fun cryptoStreamChaCha20IetfXor(
-        message: ByteArray,
-        nonce: ByteArray?,
-        key: ByteArray?,
-    ): ByteArray {
-        val ciphertext = ByteArray(message.size)
-        Clibsodium.crypto_stream_chacha20_ietf_xor(
-            c = ciphertext.uRefTo(0),
-            m = message.uRefTo(0),
-            mlen = message.size.toULong(),
-            n = nonce?.uRefTo(0),
-            k = key?.uRefTo(0),
-        )
-        return ciphertext
-    }
-
-    @OptIn(ExperimentalForeignApi::class, ExperimentalNativeApi::class)
-    actual fun cryptoStreamXChaCha20Xor(
-        messageBytes: ByteArray,
-        nonce: ByteArray,
-        key: ByteArray,
-    ): ByteArray {
-        val cipher = ByteArray(messageBytes.size)
-        val k2 = ByteArray(32)
-
-        val nonceChaCha = nonce.drop(16).toByteArray()
-        assert(nonceChaCha.size == 8)
-
-        Clibsodium.crypto_core_hchacha20(
-            out = k2.uRefTo(0),
-            nonce.uRefTo(0),
-            k = key.uRefTo(0),
-            c = null,
-        )
-
-        val resultCode =
-            Clibsodium.crypto_stream_chacha20_xor_ic(
-                c = cipher.uRefTo(0),
-                m = messageBytes.uRefTo(0),
-                mlen = messageBytes.size.toULong(),
-                n = nonceChaCha.uRefTo(0),
-                ic = 0L.toULong(),
-                k = k2.uRefTo(0),
-            )
-        return if (resultCode == 0) cipher else throw IllegalStateException("Could not decrypt message")
-    }
-}
-
-@OptIn(ExperimentalForeignApi::class)
-@Suppress("UNCHECKED_CAST")
-private fun ByteArray.uRefTo(index: Int) = refTo(index) as CValuesRef<UByteVar>
diff --git a/quartz/src/jvmMain/kotlin/com/vitorpamplona/quartz/utils/LibSodiumInstance.jvm.kt b/quartz/src/jvmMain/kotlin/com/vitorpamplona/quartz/utils/LibSodiumInstance.jvm.kt
deleted file mode 100644
index 0645caee8..000000000
--- a/quartz/src/jvmMain/kotlin/com/vitorpamplona/quartz/utils/LibSodiumInstance.jvm.kt
+++ /dev/null
@@ -1,104 +0,0 @@
-/*
- * Copyright (c) 2025 Vitor Pamplona
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy of
- * this software and associated documentation files (the "Software"), to deal in
- * the Software without restriction, including without limitation the rights to use,
- * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
- * Software, and to permit persons to whom the Software is furnished to do so,
- * subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in all
- * copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
- * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
- * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
- * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
- * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
- */
-package com.vitorpamplona.quartz.utils
-
-import com.goterl.lazysodium.LazySodiumJava
-import com.goterl.lazysodium.SodiumJava
-
-actual object LibSodiumInstance {
-    private val libSodium = SodiumJava()
-    private val lazySodium = LazySodiumJava(libSodium)
-
-    actual fun cryptoAeadXChaCha20Poly1305IetfDecrypt(
-        message: ByteArray,
-        nSec: ByteArray,
-        ciphertext: ByteArray,
-        ad: ByteArray,
-        nPub: ByteArray,
-        k: ByteArray,
-    ): Boolean =
-        lazySodium.cryptoAeadXChaCha20Poly1305IetfDecrypt(
-            message,
-            longArrayOf(message.size.toLong()),
-            nSec,
-            ciphertext,
-            ciphertext.size.toLong(),
-            ad,
-            ad.size.toLong(),
-            nPub,
-            k,
-        )
-
-    actual fun cryptoAeadXChaCha20Poly1305IetfEncrypt(
-        ciphertext: ByteArray,
-        message: ByteArray,
-        ad: ByteArray,
-        nSec: ByteArray,
-        nPub: ByteArray,
-        k: ByteArray,
-    ): Boolean =
-        lazySodium.cryptoAeadXChaCha20Poly1305IetfEncrypt(
-            ciphertext,
-            longArrayOf(ciphertext.size.toLong()),
-            message,
-            message.size.toLong(),
-            ad,
-            ad.size.toLong(),
-            nSec,
-            nPub,
-            k,
-        )
-
-    actual fun cryptoStreamChaCha20IetfXor(
-        message: ByteArray,
-        nonce: ByteArray?,
-        key: ByteArray?,
-    ): ByteArray {
-        val ciphertext = ByteArray(message.size)
-        lazySodium.cryptoStreamChaCha20IetfXor(ciphertext, message, message.size.toLong(), nonce, key)
-        return ciphertext
-    }
-
-    actual fun cryptoStreamXChaCha20Xor(
-        messageBytes: ByteArray,
-        nonce: ByteArray,
-        key: ByteArray,
-    ): ByteArray {
-        val cipher = ByteArray(messageBytes.size)
-        val k2 = ByteArray(32)
-
-        val nonceChaCha = nonce.drop(16).toByteArray()
-        assert(nonceChaCha.size == 8)
-
-        libSodium.crypto_core_hchacha20(k2, nonce, key, null)
-        val resultCode =
-            libSodium.crypto_stream_chacha20_xor_ic(
-                cipher,
-                messageBytes,
-                messageBytes.size.toLong(),
-                nonceChaCha,
-                0,
-                k2,
-            )
-
-        return if (resultCode == 0) cipher else throw IllegalStateException("Could not decrypt message")
-    }
-}