From 8303bd85bada793684b34cb59294c72c1c148d08 Mon Sep 17 00:00:00 2001
From: Jazz Turner-Baggs <473256+jazzz@users.noreply.github.com>
Date: Sat, 13 Jun 2026 08:57:52 -0700
Subject: [PATCH] Downgrade Ciphersuite

---
 core/conversations/src/conversation/group_v1.rs |  6 +++---
 core/conversations/src/inbox_v2.rs              | 11 +++++------
 2 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/core/conversations/src/conversation/group_v1.rs b/core/conversations/src/conversation/group_v1.rs
index 3763eb6..0d0d433 100644
--- a/core/conversations/src/conversation/group_v1.rs
+++ b/core/conversations/src/conversation/group_v1.rs
@@ -39,7 +39,7 @@ impl std::fmt::Debug for GroupV1Convo {
 impl GroupV1Convo {
     // Create a new conversation with the creator as the only participant.
     pub fn new<S: ExternalServices>(cx: &mut ServiceContext<S>) -> Result<Self, ChatError> {
-        let config = Self::mls_create_config();
+        let config = Self::mls_create_config(cx);
         let mls_group = MlsGroup::new(
             &cx.mls_provider,
             &cx.mls_identity,
@@ -105,9 +105,9 @@ impl GroupV1Convo {
         Ok(())
     }
 
-    fn mls_create_config() -> MlsGroupCreateConfig {
+    fn mls_create_config<S: ExternalServices>(cx: &mut ServiceContext<S>) -> MlsGroupCreateConfig {
         MlsGroupCreateConfig::builder()
-            .ciphersuite(Ciphersuite::MLS_256_XWING_CHACHA20POLY1305_SHA256_Ed25519)
+            .ciphersuite(cx.mls_provider.crypto().supported_ciphersuites()[0])
             .use_ratchet_tree_extension(true) // This is handy for now, until there is central store for this data
             .build()
     }
diff --git a/core/conversations/src/inbox_v2.rs b/core/conversations/src/inbox_v2.rs
index 7d5259c..23589ff 100644
--- a/core/conversations/src/inbox_v2.rs
+++ b/core/conversations/src/inbox_v2.rs
@@ -1,8 +1,6 @@
 mod identity;
 mod mls_provider;
 
-use crypto::Ed25519VerifyingKey;
-pub use identity::MlsIdentityProvider;
 use chat_proto::logoschat::envelope::EnvelopeV1;
 use crypto::Ed25519VerifyingKey;
 use de_mls::protos::de_mls::messages::v1::MemberWelcome;
@@ -31,6 +29,9 @@ use crate::{
 };
 use crate::{IdentId, IdentIdRef, IdentityProvider};
 
+// Downgraded from MLS_256_XWING_CHACHA20POLY1305_SHA256_Ed25519 until demls accepts an external provider
+const CIPHER_SUITE: Ciphersuite = Ciphersuite::MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519;
+
 // Define unique Identifiers derivations used in InboxV2
 fn delivery_address_for(ident_id: IdentIdRef) -> String {
     blake2b_hex::<hash_size::DeliveryAddr>(&["InboxV2|", "delivery_address|", ident_id.as_str()])
@@ -201,15 +202,13 @@ impl InboxV2 {
         cx: &ServiceContext<S>,
     ) -> Result<KeyPackage, ChatError> {
         let capabilities = Capabilities::builder()
-            .ciphersuites(vec![
-                Ciphersuite::MLS_256_XWING_CHACHA20POLY1305_SHA256_Ed25519,
-            ])
+            .ciphersuites(vec![CIPHER_SUITE])
             .extensions(vec![ExtensionType::ApplicationId])
             .build();
         let a = KeyPackage::builder()
             .leaf_node_capabilities(capabilities)
             .build(
-                Ciphersuite::MLS_256_XWING_CHACHA20POLY1305_SHA256_Ed25519,
+                CIPHER_SUITE,
                 &cx.mls_provider,
                 &cx.mls_identity,
                 cx.mls_identity.get_credential(),