diff --git a/library/src/main/java/org/xmtp/android/library/Contacts.kt b/library/src/main/java/org/xmtp/android/library/Contacts.kt
index e3ab956b1..b18fb2f23 100644
--- a/library/src/main/java/org/xmtp/android/library/Contacts.kt
+++ b/library/src/main/java/org/xmtp/android/library/Contacts.kt
@@ -4,6 +4,7 @@ import kotlinx.coroutines.runBlocking
 import org.xmtp.android.library.messages.ContactBundle
 import org.xmtp.android.library.messages.ContactBundleBuilder
 import org.xmtp.android.library.messages.Topic
+import org.xmtp.android.library.messages.walletAddress
 
 data class Contacts(
     var client: Client,
@@ -27,8 +28,14 @@ data class Contacts(
         if (response.envelopesList.isNullOrEmpty()) return null
 
         for (envelope in response.envelopesList) {
-            knownBundles[peerAddress] = ContactBundleBuilder.buildFromEnvelope(envelope)
+            val contactBundle = ContactBundleBuilder.buildFromEnvelope(envelope)
+            knownBundles[peerAddress] = contactBundle
+            val address = contactBundle.walletAddress
+            if (address == peerAddress) {
+                return contactBundle
+            }
         }
-        return ContactBundleBuilder.buildFromEnvelope(response.envelopesList.first())
+
+        return null
     }
 }
diff --git a/library/src/main/java/org/xmtp/android/library/ConversationV2.kt b/library/src/main/java/org/xmtp/android/library/ConversationV2.kt
index 47f883721..3541583dc 100644
--- a/library/src/main/java/org/xmtp/android/library/ConversationV2.kt
+++ b/library/src/main/java/org/xmtp/android/library/ConversationV2.kt
@@ -81,7 +81,7 @@ data class ConversationV2(
     }
 
     fun decode(message: MessageV2): DecodedMessage =
-        MessageV2Builder.buildDecode(message, keyMaterial = keyMaterial)
+        MessageV2Builder.buildDecode(message, keyMaterial = keyMaterial, topic = topic)
 
     fun <T> send(content: T, options: SendOptions? = null) {
         val codec = Client.codecRegistry.find(options?.contentType)
diff --git a/library/src/main/java/org/xmtp/android/library/KeyUtil.kt b/library/src/main/java/org/xmtp/android/library/KeyUtil.kt
index 878f7020c..94b6faba4 100644
--- a/library/src/main/java/org/xmtp/android/library/KeyUtil.kt
+++ b/library/src/main/java/org/xmtp/android/library/KeyUtil.kt
@@ -1,25 +1,12 @@
 package org.xmtp.android.library
 
-import org.bouncycastle.asn1.sec.SECNamedCurves
-import org.bouncycastle.crypto.params.ECDomainParameters
-import org.bouncycastle.math.ec.FixedPointCombMultiplier
-import org.bouncycastle.util.Arrays
+import org.web3j.crypto.Sign
 import org.web3j.crypto.Sign.SignatureData
 import java.math.BigInteger
 
 object KeyUtil {
     fun getPublicKey(privateKey: ByteArray): ByteArray {
-        val params = SECNamedCurves.getByName("secp256k1")
-        val curve = ECDomainParameters(params.curve, params.g, params.n, params.h)
-
-        var privKey = BigInteger(1, privateKey)
-
-        if (privKey.bitLength() > curve.n.bitLength()) {
-            privKey = privKey.mod(curve.n)
-        }
-
-        val point = FixedPointCombMultiplier().multiply(curve.getG(), privKey)
-        return Arrays.copyOfRange(point.getEncoded(false), 1, 65)
+        return Sign.publicKeyFromPrivate(BigInteger(1, privateKey)).toByteArray()
     }
 
     fun addUncompressedByte(publicKey: ByteArray): ByteArray {
diff --git a/library/src/main/java/org/xmtp/android/library/messages/MessageV2.kt b/library/src/main/java/org/xmtp/android/library/messages/MessageV2.kt
index ba19c6d0c..15cf2f826 100644
--- a/library/src/main/java/org/xmtp/android/library/messages/MessageV2.kt
+++ b/library/src/main/java/org/xmtp/android/library/messages/MessageV2.kt
@@ -25,7 +25,7 @@ class MessageV2Builder {
             }.build()
         }
 
-        fun buildDecode(message: MessageV2, keyMaterial: ByteArray): DecodedMessage {
+        fun buildDecode(message: MessageV2, keyMaterial: ByteArray, topic: String): DecodedMessage {
             val decrypted =
                 Crypto.decrypt(keyMaterial, message.ciphertext, message.headerBytes.toByteArray())
             val signed = SignedContent.parseFrom(decrypted)
@@ -64,10 +64,13 @@ class MessageV2Builder {
             }.build()
 
             if (key.walletAddress != (PublicKeyBuilder.buildFromSignedPublicKey(signed.sender.preKey).walletAddress)) {
-                throw throw XMTPException("Invalid signature")
+                throw XMTPException("Invalid signature")
             }
             val encodedMessage = EncodedContent.parseFrom(signed.payload)
             val header = MessageHeaderV2.parseFrom(message.headerBytes)
+            if (header.topic != topic) {
+                throw XMTPException("Topic mismatch")
+            }
             return DecodedMessage(
                 encodedContent = encodedMessage,
                 senderAddress = signed.sender.walletAddress,
diff --git a/library/src/test/java/org/xmtp/android/library/MessageTest.kt b/library/src/test/java/org/xmtp/android/library/MessageTest.kt
index 0510ba5a2..e87d84373 100644
--- a/library/src/test/java/org/xmtp/android/library/MessageTest.kt
+++ b/library/src/test/java/org/xmtp/android/library/MessageTest.kt
@@ -83,7 +83,8 @@ class MessageTest {
         )
         val decoded = MessageV2Builder.buildDecode(
             message1,
-            keyMaterial = invitationv1.aes256GcmHkdfSha256.keyMaterial.toByteArray()
+            keyMaterial = invitationv1.aes256GcmHkdfSha256.keyMaterial.toByteArray(),
+            topic = invitationv1.topic
         )
         val result: String? = decoded.content()
         assertEquals(result, "Yo!")