Remove weird roundabout way of doing decryption

app/src/main/java/org/thoughtcrime/securesms/ApplicationContext.java

@@ -70,7 +70,6 @@ import org.thoughtcrime.securesms.loki.activities.HomeActivity;
 import org.thoughtcrime.securesms.loki.api.BackgroundPollWorker;
 import org.thoughtcrime.securesms.loki.api.LokiPushNotificationManager;
 import org.thoughtcrime.securesms.loki.api.PublicChatManager;
-import org.thoughtcrime.securesms.loki.api.SessionProtocolImpl;
 import org.thoughtcrime.securesms.loki.database.LokiAPIDatabase;
 import org.thoughtcrime.securesms.loki.database.LokiThreadDatabase;
 import org.thoughtcrime.securesms.loki.database.LokiUserDatabase;
@@ -178,8 +177,7 @@ public class ApplicationContext extends MultiDexApplication implements Dependenc
         String userPublicKey = TextSecurePreferences.getLocalNumber(this);
         MessagingModuleConfiguration.Companion.configure(this,
                 DatabaseFactory.getStorage(this),
-                DatabaseFactory.getAttachmentProvider(this),
-                new SessionProtocolImpl(this));
+                DatabaseFactory.getAttachmentProvider(this));
         SnodeModule.Companion.configure(apiDB, broadcaster);
         if (userPublicKey != null) {
             MentionsManager.Companion.configureIfNeeded(userPublicKey, userDB);

app/src/main/java/org/thoughtcrime/securesms/database/Storage.kt

@@ -347,7 +347,7 @@ class Storage(context: Context, helper: SQLCipherOpenHelper) : Database(context,
         DatabaseFactory.getLokiAPIDatabase(context).removeLastDeletionServerID(group, server)
     }
 
-    override fun isMessageDuplicated(timestamp: Long, sender: String): Boolean {
+    override fun isDuplicateMessage(timestamp: Long, sender: String): Boolean {
         return getReceivedMessageTimestamps().contains(timestamp)
     }
 

app/src/main/java/org/thoughtcrime/securesms/loki/activities/SettingsActivity.kt

@@ -24,6 +24,7 @@ import network.loki.messenger.R
 import nl.komponents.kovenant.Promise
 import nl.komponents.kovenant.all
 import nl.komponents.kovenant.ui.alwaysUi
+import nl.komponents.kovenant.ui.successUi
 import org.session.libsession.messaging.avatars.AvatarHelper
 import org.session.libsession.messaging.open_groups.OpenGroupAPI
 import org.session.libsession.messaging.threads.Address
@@ -189,7 +190,7 @@ class SettingsActivity : PassphraseRequiredActionBarActivity() {
             promises.add(ProfilePictureUtilities.upload(profilePicture, encodedProfileKey, this))
         }
         val compoundPromise = all(promises)
-        compoundPromise.success {
+        compoundPromise.successUi { // Do this on the UI thread so that it happens before the alwaysUi clause below
             if (isUpdatingProfilePicture && profilePicture != null) {
                 AvatarHelper.setAvatar(this, Address.fromSerialized(TextSecurePreferences.getLocalNumber(this)!!), profilePicture)
                 TextSecurePreferences.setProfileAvatarId(this, SecureRandom().nextInt())
@@ -206,7 +207,7 @@ class SettingsActivity : PassphraseRequiredActionBarActivity() {
                 btnGroupNameDisplay.text = displayName
             }
             if (isUpdatingProfilePicture && profilePicture != null) {
-                profilePictureView.recycle() // clear cached image before update tje profilePictureView
+                profilePictureView.recycle() // Clear the cached image before updating
                 profilePictureView.update()
             }
             displayNameToBeUploaded = null

app/src/main/java/org/thoughtcrime/securesms/loki/protocol/ClosedGroupsProtocolV2.kt

@@ -3,6 +3,7 @@ package org.thoughtcrime.securesms.loki.protocol
 import android.content.Context
 import android.util.Log
 import com.google.protobuf.ByteString
+import org.session.libsession.messaging.sending_receiving.*
 import org.session.libsignal.libsignal.ecc.DjbECPrivateKey
 import org.session.libsignal.libsignal.ecc.DjbECPublicKey
 import org.session.libsignal.libsignal.ecc.ECKeyPair
@@ -15,12 +16,7 @@ import org.thoughtcrime.securesms.database.DatabaseFactory
 import org.thoughtcrime.securesms.database.GroupDatabase
 import org.thoughtcrime.securesms.loki.api.LokiPushNotificationManager
 import org.thoughtcrime.securesms.loki.api.LokiPushNotificationManager.ClosedGroupOperation
-import org.thoughtcrime.securesms.loki.api.SessionProtocolImpl
 import org.thoughtcrime.securesms.loki.database.LokiAPIDatabase
-import org.session.libsession.messaging.sending_receiving.MessageSender
-import org.session.libsession.messaging.sending_receiving.generateAndSendNewEncryptionKeyPair
-import org.session.libsession.messaging.sending_receiving.pendingKeyPair
-import org.session.libsession.messaging.sending_receiving.sendEncryptionKeyPair
 
 import org.session.libsession.messaging.threads.Address
 import org.session.libsession.messaging.threads.GroupRecord
@@ -330,7 +326,7 @@ object ClosedGroupsProtocolV2 {
         // Find our wrapper and decrypt it if possible
         val wrapper = closedGroupUpdate.wrappersList.firstOrNull { it.publicKey.toByteArray().toHexString() == userPublicKey } ?: return
         val encryptedKeyPair = wrapper.encryptedKeyPair.toByteArray()
-        val plaintext = SessionProtocolImpl(context).decrypt(encryptedKeyPair, userKeyPair).first
+        val plaintext = MessageDecrypter.decrypt(encryptedKeyPair, userKeyPair).first
         // Parse it
         val proto = SignalServiceProtos.KeyPair.parseFrom(plaintext)
         val keyPair = ECKeyPair(DjbECPublicKey(proto.publicKey.toByteArray().removing05PrefixIfNeeded()), DjbECPrivateKey(proto.privateKey.toByteArray()))

libsession/src/main/java/org/session/libsession/messaging/MessagingModuleConfiguration.kt

@@ -2,13 +2,11 @@ package org.session.libsession.messaging
 
 import android.content.Context
 import org.session.libsession.database.MessageDataProvider
-import org.session.libsignal.service.loki.api.crypto.SessionProtocol
 
 class MessagingModuleConfiguration(
     val context: Context,
     val storage: StorageProtocol,
-    val messageDataProvider: MessageDataProvider,
-    val sessionProtocol: SessionProtocol
+    val messageDataProvider: MessageDataProvider
 ) {
 
     companion object {
@@ -16,11 +14,10 @@ class MessagingModuleConfiguration(
 
         fun configure(context: Context,
             storage: StorageProtocol,
-            messageDataProvider: MessageDataProvider,
-            sessionProtocol: SessionProtocol
+            messageDataProvider: MessageDataProvider
         ) {
             if (Companion::shared.isInitialized) { return }
-            shared = MessagingModuleConfiguration(context, storage, messageDataProvider, sessionProtocol)
+            shared = MessagingModuleConfiguration(context, storage, messageDataProvider)
         }
     }
 }

libsession/src/main/java/org/session/libsession/messaging/StorageProtocol.kt

@@ -92,7 +92,7 @@ interface StorageProtocol {
     fun removeLastDeletionServerId(room: String, server: String)
 
     // Message Handling
-    fun isMessageDuplicated(timestamp: Long, sender: String): Boolean
+    fun isDuplicateMessage(timestamp: Long, sender: String): Boolean
     fun getReceivedMessageTimestamps(): Set<Long>
     fun addReceivedMessageTimestamp(timestamp: Long)
     fun removeReceivedMessageTimestamps(timestamps: Set<Long>)

libsession/src/main/java/org/session/libsession/messaging/sending_receiving/MessageDecrypter.kt

@@ -1,26 +1,21 @@
-package org.thoughtcrime.securesms.loki.api
+package org.session.libsession.messaging.sending_receiving
 
-import android.content.Context
 import android.util.Log
 import com.goterl.lazycode.lazysodium.LazySodiumAndroid
 import com.goterl.lazycode.lazysodium.SodiumAndroid
 import com.goterl.lazycode.lazysodium.interfaces.Box
 import com.goterl.lazycode.lazysodium.interfaces.Sign
-
-import org.session.libsignal.utilities.Hex
-
 import org.session.libsignal.libsignal.ecc.ECKeyPair
-import org.session.libsignal.service.loki.api.crypto.SessionProtocol
 import org.session.libsignal.service.loki.utilities.hexEncodedPublicKey
 import org.session.libsignal.service.loki.utilities.removing05PrefixIfNeeded
 import org.session.libsignal.service.loki.utilities.toHexString
-import org.session.libsession.utilities.KeyPairUtilities
+import org.session.libsignal.utilities.Hex
 
-class SessionProtocolImpl(private val context: Context) : SessionProtocol {
+object MessageDecrypter {
 
     private val sodium by lazy { LazySodiumAndroid(SodiumAndroid()) }
 
-    override fun decrypt(ciphertext: ByteArray, x25519KeyPair: ECKeyPair): Pair<ByteArray, String> {
+    public fun decrypt(ciphertext: ByteArray, x25519KeyPair: ECKeyPair): Pair<ByteArray, String> {
         val recipientX25519PrivateKey = x25519KeyPair.privateKey.serialize()
         val recipientX25519PublicKey = Hex.fromStringCondensed(x25519KeyPair.hexEncodedPublicKey.removing05PrefixIfNeeded())
         val signatureSize = Sign.BYTES
@@ -32,9 +27,9 @@ class SessionProtocolImpl(private val context: Context) : SessionProtocol {
             sodium.cryptoBoxSealOpen(plaintextWithMetadata, ciphertext, ciphertext.size.toLong(), recipientX25519PublicKey, recipientX25519PrivateKey)
         } catch (exception: Exception) {
             Log.d("Loki", "Couldn't decrypt message due to error: $exception.")
-            throw SessionProtocol.Exception.DecryptionFailed
+            throw MessageReceiver.Error.DecryptionFailed
         }
-        if (plaintextWithMetadata.size <= (signatureSize + ed25519PublicKeySize)) { throw SessionProtocol.Exception.DecryptionFailed }
+        if (plaintextWithMetadata.size <= (signatureSize + ed25519PublicKeySize)) { throw MessageReceiver.Error.DecryptionFailed }
         // 2. ) Get the message parts
         val signature = plaintextWithMetadata.sliceArray(plaintextWithMetadata.size - signatureSize until plaintextWithMetadata.size)
         val senderED25519PublicKey = plaintextWithMetadata.sliceArray(plaintextWithMetadata.size - (signatureSize + ed25519PublicKeySize) until plaintextWithMetadata.size - signatureSize)
@@ -43,10 +38,10 @@ class SessionProtocolImpl(private val context: Context) : SessionProtocol {
         val verificationData = (plaintext + senderED25519PublicKey + recipientX25519PublicKey)
         try {
             val isValid = sodium.cryptoSignVerifyDetached(signature, verificationData, verificationData.size, senderED25519PublicKey)
-            if (!isValid) { throw SessionProtocol.Exception.InvalidSignature }
+            if (!isValid) { throw MessageReceiver.Error.InvalidSignature }
         } catch (exception: Exception) {
             Log.d("Loki", "Couldn't verify message signature due to error: $exception.")
-            throw SessionProtocol.Exception.InvalidSignature
+            throw MessageReceiver.Error.InvalidSignature
         }
         // 4. ) Get the sender's X25519 public key
         val senderX25519PublicKey = ByteArray(Sign.CURVE25519_PUBLICKEYBYTES)

libsession/src/main/java/org/session/libsession/messaging/sending_receiving/MessageReceiver.kt

@@ -10,35 +10,25 @@ import org.session.libsignal.service.internal.push.SignalServiceProtos
 
 object MessageReceiver {
 
-    private val lastEncryptionKeyPairRequest = mutableMapOf<String, Long>()
-
-    internal sealed class Error(val description: String) : Exception(description) {
+    internal sealed class Error(message: String) : Exception(message) {
         object DuplicateMessage: Error("Duplicate message.")
         object InvalidMessage: Error("Invalid message.")
         object UnknownMessage: Error("Unknown message type.")
         object UnknownEnvelopeType: Error("Unknown envelope type.")
-        object NoUserX25519KeyPair: Error("Couldn't find user X25519 key pair.")
-        object NoUserED25519KeyPair: Error("Couldn't find user ED25519 key pair.")
+        object DecryptionFailed : Exception("Couldn't decrypt message.")
         object InvalidSignature: Error("Invalid message signature.")
         object NoData: Error("Received an empty envelope.")
         object SenderBlocked: Error("Received a message from a blocked user.")
         object NoThread: Error("Couldn't find thread for message.")
         object SelfSend: Error("Message addressed at self.")
-        object ParsingFailed : Error("Couldn't parse ciphertext message.")
         // Shared sender keys
         object InvalidGroupPublicKey: Error("Invalid group public key.")
         object NoGroupKeyPair: Error("Missing group key pair.")
 
         internal val isRetryable: Boolean = when (this) {
-            is DuplicateMessage -> false
-            is InvalidMessage -> false
-            is UnknownMessage -> false
-            is UnknownEnvelopeType -> false
-            is InvalidSignature -> false
-            is NoData -> false
-            is NoThread -> false
-            is SenderBlocked -> false
-            is SelfSend -> false
+            is DuplicateMessage, is InvalidMessage, is UnknownMessage,
+            is UnknownEnvelopeType, is InvalidSignature, is NoData,
+            is SenderBlocked, is SelfSend -> false
             else -> true
         }
     }
@@ -46,13 +36,15 @@ object MessageReceiver {
     internal fun parse(data: ByteArray, openGroupServerID: Long?, isRetry: Boolean = false): Pair<Message, SignalServiceProtos.Content> {
         val storage = MessagingModuleConfiguration.shared.storage
         val userPublicKey = storage.getUserPublicKey()
-        val isOpenGroupMessage = openGroupServerID != null
+        val isOpenGroupMessage = (openGroupServerID != null)
         // Parse the envelope
         val envelope = SignalServiceProtos.Envelope.parseFrom(data)
         // If the message failed to process the first time around we retry it later (if the error is retryable). In this case the timestamp
         // will already be in the database but we don't want to treat the message as a duplicate. The isRetry flag is a simple workaround
         // for this issue.
-        if (storage.isMessageDuplicated(envelope.timestamp, GroupUtil.doubleEncodeGroupID(envelope.source)) && !isRetry) throw Error.DuplicateMessage
+        if (storage.isDuplicateMessage(envelope.timestamp, GroupUtil.doubleEncodeGroupID(envelope.source)) && !isRetry) {
+            throw Error.DuplicateMessage
+        }
         // Decrypt the contents
         val ciphertext = envelope.content ?: throw Error.NoData
         var plaintext: ByteArray? = null
@@ -65,7 +57,7 @@ object MessageReceiver {
             when (envelope.type) {
                 SignalServiceProtos.Envelope.Type.SESSION_MESSAGE -> {
                     val userX25519KeyPair = MessagingModuleConfiguration.shared.storage.getUserX25519KeyPair()
-                    val decryptionResult = MessageReceiverDecryption.decryptWithSessionProtocol(ciphertext.toByteArray(), userX25519KeyPair)
+                    val decryptionResult = MessageDecrypter.decrypt(ciphertext.toByteArray(), userX25519KeyPair)
                     plaintext = decryptionResult.first
                     sender = decryptionResult.second
                 }
@@ -81,7 +73,7 @@ object MessageReceiver {
                     var encryptionKeyPair = encryptionKeyPairs.removeLast()
                     fun decrypt() {
                         try {
-                            val decryptionResult = MessageReceiverDecryption.decryptWithSessionProtocol(ciphertext.toByteArray(), encryptionKeyPair)
+                            val decryptionResult = MessageDecrypter.decrypt(ciphertext.toByteArray(), encryptionKeyPair)
                             plaintext = decryptionResult.first
                             sender = decryptionResult.second
                         } catch (e: Exception) {
@@ -100,9 +92,9 @@ object MessageReceiver {
             }
         }
         // Don't process the envelope any further if the message has been handled already
-        if (storage.isMessageDuplicated(envelope.timestamp, sender!!) && !isRetry) throw Error.DuplicateMessage
+        if (storage.isDuplicateMessage(envelope.timestamp, sender!!) && !isRetry) throw Error.DuplicateMessage
         // Don't process the envelope any further if the sender is blocked
-        if (isBlock(sender!!)) throw Error.SenderBlocked
+        if (isBlocked(sender!!)) throw Error.SenderBlocked
         // Parse the proto
         val proto = SignalServiceProtos.Content.parseFrom(PushTransportDetails.getStrippedPaddingMessageBody(plaintext))
         // Parse the message
@@ -113,7 +105,7 @@ object MessageReceiver {
             ExpirationTimerUpdate.fromProto(proto) ?:
             ConfigurationMessage.fromProto(proto) ?:
             VisibleMessage.fromProto(proto) ?: throw Error.UnknownMessage
-        // Ignore self sends if needed
+        // Ignore self send if needed
         if (!message.isSelfSendValid && sender == userPublicKey) throw Error.SelfSend
         // Guard against control messages in open groups
         if (isOpenGroupMessage && message !is VisibleMessage) throw Error.InvalidMessage

libsession/src/main/java/org/session/libsession/messaging/sending_receiving/MessageReceiverDecryption.kt

@@ -1,11 +0,0 @@
-package org.session.libsession.messaging.sending_receiving
-
-import org.session.libsession.messaging.MessagingModuleConfiguration
-import org.session.libsignal.libsignal.ecc.ECKeyPair
-
-object MessageReceiverDecryption {
-
-    internal fun decryptWithSessionProtocol(ciphertext: ByteArray, x25519KeyPair: ECKeyPair): Pair<ByteArray, String> {
-        return MessagingModuleConfiguration.shared.sessionProtocol.decrypt(ciphertext, x25519KeyPair)
-    }
-}

libsession/src/main/java/org/session/libsession/messaging/sending_receiving/ReceivedMessageHandler.kt

@@ -34,7 +34,7 @@ import java.security.MessageDigest
 import java.util.*
 import kotlin.collections.ArrayList
 
-internal fun MessageReceiver.isBlock(publicKey: String): Boolean {
+internal fun MessageReceiver.isBlocked(publicKey: String): Boolean {
     val context = MessagingModuleConfiguration.shared.context
     val recipient = Recipient.from(context, Address.fromSerialized(publicKey), false)
     return recipient.isBlocked
@@ -323,7 +323,7 @@ private fun MessageReceiver.handleClosedGroupEncryptionKeyPair(message: ClosedGr
     // Find our wrapper and decrypt it if possible
     val wrapper = kind.wrappers.firstOrNull { it.publicKey!! == userPublicKey } ?: return
     val encryptedKeyPair = wrapper.encryptedKeyPair!!.toByteArray()
-    val plaintext = MessageReceiverDecryption.decryptWithSessionProtocol(encryptedKeyPair, userKeyPair).first
+    val plaintext = MessageDecrypter.decrypt(encryptedKeyPair, userKeyPair).first
     // Parse it
     val proto = SignalServiceProtos.KeyPair.parseFrom(plaintext)
     val keyPair = ECKeyPair(DjbECPublicKey(proto.publicKey.toByteArray().removing05PrefixIfNeeded()), DjbECPrivateKey(proto.privateKey.toByteArray()))

libsignal/src/main/java/org/session/libsignal/service/api/crypto/SignalServiceCipher.java

@@ -31,8 +31,6 @@ import org.session.libsignal.service.internal.push.SignalServiceProtos.Content;
 import org.session.libsignal.service.internal.push.SignalServiceProtos.DataMessage;
 import org.session.libsignal.service.internal.push.SignalServiceProtos.ReceiptMessage;
 import org.session.libsignal.service.internal.push.SignalServiceProtos.TypingMessage;
-import org.session.libsignal.service.loki.api.crypto.SessionProtocol;
-import org.session.libsignal.service.loki.api.crypto.SessionProtocolUtilities;
 import org.session.libsignal.service.loki.LokiAPIDatabaseProtocol;
 
 import java.util.ArrayList;
@@ -51,13 +49,10 @@ public class SignalServiceCipher {
   @SuppressWarnings("unused")
   private static final String TAG = SignalServiceCipher.class.getSimpleName();
 
-  private final SessionProtocol                  sessionProtocolImpl;
   private final LokiAPIDatabaseProtocol          apiDB;
 
-  public SignalServiceCipher(SessionProtocol sessionProtocolImpl,
-                             LokiAPIDatabaseProtocol apiDB)
+  public SignalServiceCipher(LokiAPIDatabaseProtocol apiDB)
   {
-    this.sessionProtocolImpl  = sessionProtocolImpl;
     this.apiDB                = apiDB;
   }
 
@@ -125,27 +120,7 @@ public class SignalServiceCipher {
 
   protected Plaintext decrypt(SignalServiceEnvelope envelope, byte[] ciphertext) throws InvalidMetadataMessageException
   {
-    byte[] paddedMessage;
-    Metadata metadata;
-
-    if (envelope.isClosedGroupCiphertext()) {
-      String groupPublicKey = envelope.getSource();
-      kotlin.Pair<byte[], String> plaintextAndSenderPublicKey = SessionProtocolUtilities.INSTANCE.decryptClosedGroupCiphertext(ciphertext, groupPublicKey, apiDB, sessionProtocolImpl);
-      paddedMessage = plaintextAndSenderPublicKey.getFirst();
-      String senderPublicKey = plaintextAndSenderPublicKey.getSecond();
-      metadata = new Metadata(senderPublicKey, 1, envelope.getTimestamp(), false);
-    } else if (envelope.isUnidentifiedSender()) {
-      ECKeyPair userX25519KeyPair = apiDB.getUserX25519KeyPair();
-      kotlin.Pair<byte[], String> plaintextAndSenderPublicKey = sessionProtocolImpl.decrypt(ciphertext, userX25519KeyPair);
-      paddedMessage = plaintextAndSenderPublicKey.getFirst();
-      String senderPublicKey = plaintextAndSenderPublicKey.getSecond();
-      metadata = new Metadata(senderPublicKey, 1, envelope.getTimestamp(), false);
-    } else {
-      throw new InvalidMetadataMessageException("Unknown type: " + envelope.getType());
-    }
-    byte[] data = PushTransportDetails.getStrippedPaddingMessageBody(paddedMessage);
-
-    return new Plaintext(metadata, data);
+    throw new IllegalStateException("This shouldn't be used anymore");
   }
 
   private SignalServiceDataMessage createSignalServiceMessage(Metadata metadata, DataMessage content) throws ProtocolInvalidMessageException {

libsignal/src/main/java/org/session/libsignal/service/loki/SessionProtocol.kt

@@ -1,53 +0,0 @@
-package org.session.libsignal.service.loki.api.crypto
-
-import org.session.libsignal.libsignal.ecc.ECKeyPair
-import org.session.libsignal.service.loki.LokiAPIDatabaseProtocol
-
-interface SessionProtocol {
-
-    sealed class Exception(val description: String) : kotlin.Exception(description) {
-        // Encryption
-        object NoUserED25519KeyPair : Exception("Couldn't find user ED25519 key pair.")
-        object SigningFailed : Exception("Couldn't sign message.")
-        object EncryptionFailed : Exception("Couldn't encrypt message.")
-        // Decryption
-        object NoData : Exception("Received an empty envelope.")
-        object InvalidGroupPublicKey : Exception("Invalid group public key.")
-        object NoGroupKeyPair : Exception("Missing group key pair.")
-        object DecryptionFailed : Exception("Couldn't decrypt message.")
-        object InvalidSignature : Exception("Invalid message signature.")
-    }
-    /**
-     * Decrypts `ciphertext` using the Session protocol and `x25519KeyPair`.
-     *
-     * @param ciphertext the data to decrypt.
-     * @param x25519KeyPair the key pair to use for decryption. This could be the current user's key pair, or the key pair of a closed group.
-     *
-     * @return the padded plaintext.
-     */
-    fun decrypt(ciphertext: ByteArray, x25519KeyPair: ECKeyPair): Pair<ByteArray, String>
-}
-
-object SessionProtocolUtilities {
-
-    fun decryptClosedGroupCiphertext(ciphertext: ByteArray, groupPublicKey: String, apiDB: LokiAPIDatabaseProtocol, sessionProtocolImpl: SessionProtocol): Pair<ByteArray, String> {
-        val encryptionKeyPairs = apiDB.getClosedGroupEncryptionKeyPairs(groupPublicKey).toMutableList()
-        if (encryptionKeyPairs.isEmpty()) { throw SessionProtocol.Exception.NoGroupKeyPair }
-        // Loop through all known group key pairs in reverse order (i.e. try the latest key pair first (which'll more than
-        // likely be the one we want) but try older ones in case that didn't work)
-        var encryptionKeyPair = encryptionKeyPairs.removeAt(encryptionKeyPairs.lastIndex)
-        fun decrypt(): Pair<ByteArray, String> {
-            try {
-                return sessionProtocolImpl.decrypt(ciphertext, encryptionKeyPair)
-            } catch(exception: Exception) {
-                if (encryptionKeyPairs.isNotEmpty()) {
-                    encryptionKeyPair = encryptionKeyPairs.removeAt(encryptionKeyPairs.lastIndex)
-                    return decrypt()
-                } else {
-                    throw exception
-                }
-            }
-        }
-        return decrypt()
-    }
-}