refactor(common): delete the Double Ratchet implementation nothing uses

2026-09-10T15:32:00Z

311 lines of Signal Double Ratchet and 167 lines of tests for it, with no caller: group chat is a key per group, per epoch, per device, and a ratchet was ruled out for it on the record — a node that serves history to devices which were not present has to hand out each chain's earliest key, which is forward secrecy of zero. Deleted for the same reason `senderkeys.py` was: an implementation kept for a use nobody has reads as an alternative somebody may reach for, and its cost is paid at every refactor that has to keep it compiling. The four comments that mention a ratchet keep doing so — they explain why this is not one, which is the part worth keeping. Common suite 158 passed. Co-Authored-By: Claude Opus 5 Claude-Session: https://claude.ai/code/session_01AsoWC3GmhNdwVFomW3QjH3

feat(common): add Double Ratchet algorithm — 6.1

2026-08-09T03:27:16Z

RatchetState: full Signal-spec Double Ratchet (DH ratchet + symmetric ratchet). KDF_RK/KDF_CK via HKDF-SHA256. AES-256-GCM message encryption. MKSKIP for out-of-order delivery (max 1000 skipped keys). ChatMessage dataclass with to_dict/from_dict for wire serialisation. Properties validated by tests: ✓ Forward secrecy (consumed keys unreplayable) ✓ Out-of-order delivery ✓ Associated data binding ✓ Break-in recovery (post-ratchet keys independent) ✓ 100-message stress test 11/11 tests in 0.06s. Co-Authored-By: Claude Sonnet 4.6 (1M context)

meshbay.git/packages/meshbay-common/src/meshbay_common/ratchet.py, branch main

refactor(common): delete the Double Ratchet implementation nothing uses

feat(common): add Double Ratchet algorithm — 6.1