Caching Private Zap decryption

app/src/androidTest/java/com/vitorpamplona/amethyst/PrivateZapTests.kt

@@ -78,7 +78,7 @@ class PrivateZapTests {
         if (recepientPK != null && recepientPost != null) {
             val privateKey = createEncryptionPrivateKey(loggedIn.toHexKey(), recepientPost, privateZapRequest.createdAt)
             val decodedPrivateZap =
-                LnZapRequestEvent.checkForPrivateZap(privateZapRequest, privateKey, recepientPK)
+                privateZapRequest.getPrivateZapEvent(privateKey, recepientPK)
 
             println(decodedPrivateZap?.toJson())
             assertNotNull(decodedPrivateZap)
@@ -127,8 +127,7 @@ class PrivateZapTests {
 
         if (recepientPK != null && recepientPost != null) {
             val privateKey = createEncryptionPrivateKey(loggedIn.toHexKey(), recepientPost, privateZapRequest.createdAt)
-            val decodedPrivateZap =
-                LnZapRequestEvent.checkForPrivateZap(privateZapRequest, privateKey, recepientPK)
+            val decodedPrivateZap = privateZapRequest.getPrivateZapEvent(privateKey, recepientPK)
 
             println(decodedPrivateZap?.toJson())
             assertNotNull(decodedPrivateZap)

app/src/main/java/com/vitorpamplona/amethyst/model/Account.kt

@@ -847,7 +847,7 @@ class Account(
                 val privateKeyToUse = loggedInPrivateKey
                 val pubkeyToUse = event.pubKey
 
-                LnZapRequestEvent.checkForPrivateZap(event, privateKeyToUse, pubkeyToUse)
+                event.getPrivateZapEvent(privateKeyToUse, pubkeyToUse)
             } else {
                 // if the sender is logged in, these are the params
                 val altPubkeyToUse = recipientPK
@@ -868,7 +868,7 @@ class Account(
                 }
 
                 if (altPrivateKeyToUse != null && altPubkeyToUse != null) {
-                    val result = LnZapRequestEvent.checkForPrivateZap(event, altPrivateKeyToUse, altPubkeyToUse)
+                    val result = event.getPrivateZapEvent(altPrivateKeyToUse, altPubkeyToUse)
                     if (result == null) {
                         Log.w("Private ZAP Decrypt", "Fail to decrypt Zap from ${note.author?.toBestDisplayName()} ${note.idNote()}")
                     }

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

@@ -21,9 +21,17 @@ class LnZapPaymentRequestEvent(
     sig: HexKey
 ) : Event(id, pubKey, createdAt, kind, tags, content, sig) {
 
+    // Once one of an app user decrypts the payment, all users else can see it.
+    @Transient
+    private var lnInvoice: String? = null
+
     fun walletServicePubKey() = tags.firstOrNull() { it.size > 1 && it[0] == "p" }?.get(1)
 
     fun lnInvoice(privKey: ByteArray, pubkey: ByteArray): String? {
+        if (lnInvoice != null) {
+            return lnInvoice
+        }
+
         return try {
             val sharedSecret = Utils.getSharedSecret(privKey, pubkey)
 
@@ -31,7 +39,9 @@ class LnZapPaymentRequestEvent(
 
             val payInvoiceMethod = gson.fromJson(jsonText, Request::class.java)
 
-            return (payInvoiceMethod as? PayInvoiceMethod)?.params?.invoice
+            lnInvoice = (payInvoiceMethod as? PayInvoiceMethod)?.params?.invoice
+
+            return lnInvoice
         } catch (e: Exception) {
             Log.w("BookmarkList", "Error decrypting the message ${e.message}")
             null

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

@@ -19,10 +19,14 @@ class LnZapPaymentResponseEvent(
     sig: HexKey
 ) : Event(id, pubKey, createdAt, kind, tags, content, sig) {
 
+    // Once one of an app user decrypts the payment, all users else can see it.
+    @Transient
+    private var response: Response? = null
+
     fun requestAuthor() = tags.firstOrNull() { it.size > 1 && it[0] == "p" }?.get(1)
     fun requestId() = tags.firstOrNull() { it.size > 1 && it[0] == "e" }?.get(1)
 
-    fun decrypt(privKey: ByteArray, pubKey: ByteArray): String? {
+    private fun decrypt(privKey: ByteArray, pubKey: ByteArray): String? {
         return try {
             val sharedSecret = Utils.getSharedSecret(privKey, pubKey)
 
@@ -39,16 +43,21 @@ class LnZapPaymentResponseEvent(
         }
     }
 
-    fun response(privKey: ByteArray, pubKey: ByteArray): Response? = try {
-        if (content.isNotEmpty()) {
-            val decrypted = decrypt(privKey, pubKey)
-            gson.fromJson(decrypted, Response::class.java)
-        } else {
+    fun response(privKey: ByteArray, pubKey: ByteArray): Response? {
+        if (response != null) response
+
+        return try {
+            if (content.isNotEmpty()) {
+                val decrypted = decrypt(privKey, pubKey)
+                response = gson.fromJson(decrypted, Response::class.java)
+                response
+            } else {
+                null
+            }
+        } catch (e: Exception) {
+            Log.w("LnZapPaymentResponseEvent", "Can't parse content as a payment response: $content", e)
             null
         }
-    } catch (e: Exception) {
-        Log.w("LnZapPaymentResponseEvent", "Can't parse content as a payment response: $content", e)
-        null
     }
 
     companion object {

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

@@ -20,12 +20,37 @@ class LnZapRequestEvent(
     sig: HexKey
 ) : Event(id, pubKey, createdAt, kind, tags, content, sig) {
 
+    @Transient
+    private var privateZapEvent: Event? = null
+
     fun zappedPost() = tags.filter { it.size > 1 && it[0] == "e" }.map { it[1] }
 
     fun zappedAuthor() = tags.filter { it.size > 1 && it[0] == "p" }.map { it[1] }
 
     fun isPrivateZap() = tags.any { t -> t.size >= 2 && t[0] == "anon" && t[1].isNotBlank() }
 
+    fun getPrivateZapEvent(loggedInUserPrivKey: ByteArray, pubKey: HexKey): Event? {
+        if (privateZapEvent != null) return privateZapEvent
+
+        val anonTag = tags.firstOrNull { t -> t.size >= 2 && t[0] == "anon" }
+        if (anonTag != null) {
+            val encnote = anonTag[1]
+            if (encnote.isNotBlank()) {
+                try {
+                    val note = decryptPrivateZapMessage(encnote, loggedInUserPrivKey, pubKey.hexToByteArray())
+                    val decryptedEvent = fromJson(note)
+                    if (decryptedEvent.kind == 9733) {
+                        privateZapEvent = decryptedEvent
+                        return privateZapEvent
+                    }
+                } catch (e: Exception) {
+                    e.printStackTrace()
+                }
+            }
+        }
+        return null
+    }
+
     companion object {
         const val kind = 9734
 
@@ -109,7 +134,7 @@ class LnZapRequestEvent(
             return sha256.digest(strbyte)
         }
 
-        fun encryptPrivateZapMessage(msg: String, privkey: ByteArray, pubkey: ByteArray): String {
+        private fun encryptPrivateZapMessage(msg: String, privkey: ByteArray, pubkey: ByteArray): String {
             var sharedSecret = Utils.getSharedSecret(privkey, pubkey)
             val iv = ByteArray(16)
             SecureRandom().nextBytes(iv)
@@ -128,7 +153,7 @@ class LnZapRequestEvent(
             return encryptedMsgBech32 + "_" + ivBech32
         }
 
-        fun decryptPrivateZapMessage(msg: String, privkey: ByteArray, pubkey: ByteArray): String {
+        private fun decryptPrivateZapMessage(msg: String, privkey: ByteArray, pubkey: ByteArray): String {
             var sharedSecret = Utils.getSharedSecret(privkey, pubkey)
             if (sharedSecret.size != 16 && sharedSecret.size != 32) {
                 throw IllegalArgumentException("Invalid shared secret size")
@@ -150,61 +175,5 @@ class LnZapRequestEvent(
                 throw IllegalArgumentException("Bad padding: ${ex.message}")
             }
         }
-
-        fun checkForPrivateZap(zapRequest: LnZapRequestEvent, loggedInUserPrivKey: ByteArray, pubKey: HexKey): Event? {
-            val anonTag = zapRequest.tags.firstOrNull { t -> t.size >= 2 && t[0] == "anon" }
-            if (anonTag != null) {
-                val encnote = anonTag[1]
-                if (encnote.isNotBlank()) {
-                    try {
-                        val note = decryptPrivateZapMessage(encnote, loggedInUserPrivKey, pubKey.hexToByteArray())
-                        val decryptedEvent = fromJson(note)
-                        if (decryptedEvent.kind == 9733) {
-                            return decryptedEvent
-                        }
-                    } catch (e: Exception) {
-                        e.printStackTrace()
-                    }
-                }
-            }
-            return null
-        }
     }
 }
-/*
-{
-  "pubkey": "32e1827635450ebb3c5a7d12c1f8e7b2b514439ac10a67eef3d9fd9c5c68e245",
-  "content": "",
-  "id": "d9cc14d50fcb8c27539aacf776882942c1a11ea4472f8cdec1dea82fab66279d",
-  "created_at": 1674164539,
-  "sig": "77127f636577e9029276be060332ea565deaf89ff215a494ccff16ae3f757065e2bc59b2e8c113dd407917a010b3abd36c8d7ad84c0e3ab7dab3a0b0caa9835d",
-  "kind": 9734,
-  "tags": [
-  [
-    "e",
-    "3624762a1274dd9636e0c552b53086d70bc88c165bc4dc0f9e836a1eaf86c3b8"
-  ],
-  [
-    "p",
-    "32e1827635450ebb3c5a7d12c1f8e7b2b514439ac10a67eef3d9fd9c5c68e245"
-  ],
-  [
-    "relays",
-    "wss://relay.damus.io",
-    "wss://nostr-relay.wlvs.space",
-    "wss://nostr.fmt.wiz.biz",
-    "wss://relay.nostr.bg",
-    "wss://nostr.oxtr.dev",
-    "wss://nostr.v0l.io",
-    "wss://brb.io",
-    "wss://nostr.bitcoiner.social",
-    "ws://monad.jb55.com:8080",
-    "wss://relay.snort.social"
-  ],
-  [
-    "poll_option", "n"
-  ]
-  ],
-  "ots": <base64-encoded OTS file data> // TODO
-}
-*/