feat: implement MLS cryptographic engine in pure Kotlin (Phase 3)
Implements the core MLS (RFC 9420) engine for Marmot Protocol integration,
targeting ciphersuite 0x0001 (DHKEM-X25519, AES-128-GCM, SHA-256, Ed25519).
Components:
- codec/: TLS presentation language encoder/decoder (RFC 8446 Section 3)
- crypto/: Ed25519 signatures, X25519 ECDH, HPKE (RFC 9180), MlsCryptoProvider
with ExpandWithLabel, DeriveSecret, SignWithLabel, EncryptWithLabel
- tree/: Left-balanced binary tree, LeafNode/ParentNode, RatchetTree with
TreeKEM encap/decap, tree hashing, resolution, path secret derivation
- schedule/: Key schedule (epoch secret derivation chain), SecretTree
(per-sender encryption ratchets), MLS-Exporter function
- framing/: MLSMessage, PublicMessage, PrivateMessage, content types
- messages/: Proposal (Add/Remove/Update/SelfRemove), Commit, UpdatePath,
Welcome, GroupInfo, GroupContext, KeyPackage, GroupSecrets
- group/: MlsGroup high-level API (create, join via Welcome, add/remove
members, encrypt/decrypt messages, export keys for Marmot outer layer)
Crypto uses expect/actual pattern: JVM/Android via java.security (EdDSA, XDH),
native platforms stubbed for future implementation. Reuses existing Quartz
primitives (AESGCM, HKDF, SHA-256, HMAC, ChaCha20-Poly1305).
Includes tests for TLS codec, binary tree arithmetic, and MLS type roundtrips.
https://claude.ai/code/session_01966YzookEUQDwszM3YCgeR
Claude
119f9dd966