Correctly managing Shared Secrets

app/src/main/java/com/vitorpamplona/amethyst/service/CryptoUtils.kt

@@ -65,7 +65,7 @@ object CryptoUtils {
     }
 
     fun encryptXChaCha(msg: String, privateKey: ByteArray, pubKey: ByteArray): EncryptedInfo {
-        val sharedSecret = getSharedSecret(privateKey, pubKey)
+        val sharedSecret = getSharedSecretXChaCha(privateKey, pubKey)
         return encryptXChaCha(msg, sharedSecret)
     }
 
@@ -94,7 +94,7 @@ object CryptoUtils {
     }
 
     fun decryptXChaCha(encryptedInfo: EncryptedInfo, privateKey: ByteArray, pubKey: ByteArray): String {
-        val sharedSecret = getSharedSecret(privateKey, pubKey)
+        val sharedSecret = getSharedSecretXChaCha(privateKey, pubKey)
         return decryptXChaCha(encryptedInfo, sharedSecret)
     }
 
@@ -132,6 +132,12 @@ object CryptoUtils {
      */
     fun getSharedSecret(privateKey: ByteArray, pubKey: ByteArray): ByteArray =
         secp256k1.pubKeyTweakMul(Hex.decode("02") + pubKey, privateKey).copyOfRange(1, 33)
+
+    /**
+     * @return 32B shared secret
+     */
+    fun getSharedSecretXChaCha(privateKey: ByteArray, pubKey: ByteArray): ByteArray =
+        sha256(secp256k1.pubKeyTweakMul(Hex.decode("02") + pubKey, privateKey).copyOfRange(1, 33))
 }
 
 fun Int.toByteArray(): ByteArray {

app/src/main/java/com/vitorpamplona/amethyst/service/StringUtils.kt

@@ -3,7 +3,6 @@ package com.vitorpamplona.amethyst.service
 import com.vitorpamplona.amethyst.ui.actions.ImmutableListOfLists
 
 fun String.isUTF16Char(pos: Int): Boolean {
-    println("Test $pos ${Character.charCount(this.codePointAt(pos))}")
     return Character.charCount(this.codePointAt(pos)) == 2
 }
 

app/src/main/java/com/vitorpamplona/amethyst/service/model/GiftWrapEvent.kt

@@ -30,7 +30,7 @@ class GiftWrapEvent(
     }
 
     fun unwrap(privKey: ByteArray) = try {
-        plainContent(privKey)?.let { println("$it"); fromJson(it, Client.lenient) }
+        plainContent(privKey)?.let { fromJson(it, Client.lenient) }
     } catch (e: Exception) {
         Log.e("UnwrapError", "Couldn't Decrypt the content", e)
         null
@@ -40,17 +40,13 @@ class GiftWrapEvent(
         if (content.isBlank()) return null
 
         return try {
-            val sharedSecret = CryptoUtils.getSharedSecret(privKey, pubKey.hexToByteArray())
+            val sharedSecret = CryptoUtils.getSharedSecretXChaCha(privKey, pubKey.hexToByteArray())
 
             val toDecrypt = gson.fromJson<EncryptedInfo>(
                 content,
                 EncryptedInfo::class.java
             )
 
-            println(toDecrypt.ciphertext)
-            println(toDecrypt.nonce)
-            println(toDecrypt.v)
-
             return CryptoUtils.decryptXChaCha(toDecrypt, sharedSecret)
         } catch (e: Exception) {
             Log.w("GeneralList", "Error decrypting the message ${e.message}")
@@ -69,7 +65,7 @@ class GiftWrapEvent(
             createdAt: Long = TimeUtils.now()
         ): GiftWrapEvent {
             val privateKey = CryptoUtils.privkeyCreate() // GiftWrap is always a random key
-            val sharedSecret = CryptoUtils.getSharedSecret(privateKey, recipientPubKey.hexToByteArray())
+            val sharedSecret = CryptoUtils.getSharedSecretXChaCha(privateKey, recipientPubKey.hexToByteArray())
 
             val content = gson.toJson(
                 CryptoUtils.encryptXChaCha(