RFC: versioned authenticated environment envelope

Summary

Specify a versioned environment-secret envelope that replaces the Stacks reference implementation simplified public/private construction with X25519 key agreement, HKDF-SHA-256 key derivation, and AES-256-GCM authenticated encryption while retaining an explicit legacy-read migration path.

Deliverables

• Versioned envelope and canonical binary layout
• X25519 key serialization and ephemeral-static key agreement
• HKDF salt/info and AES-GCM nonce/tag sizes
• Authenticated metadata and strict parsing/error behavior
• Legacy read/new write migration window
• Rotation, revocation, recovery, and logging guarantees
• Independent security review

Implementation and governance status

The proposal is published as RFC 0005 in ea9dbe4. Reference implementation and tests are in stacksjs/stacks draft PR #2064, primarily commit ffa42cd. Independent review remains tracked in stacksjs/stacks#2061. The RFC remains Proposed through the public review window ending 2026-08-20; implementation does not imply acceptance or production ratification.

Related work

• stacksjs/stacks#2058
• stacksjs/stacks#2060
• stacksjs/stacks#2061
• stacksjs/stacks#2064

Implementation is available for review in stacksjs/stacks draft PR /stacks/stacks/pull/2064, primarily commit ffa42cd. It implements the versioned X25519/HKDF-SHA-256/AES-256-GCM envelope, authenticated metadata, strict parsing/generic failure behavior, legacy read-only migration, rollback-safe rotation, tests, and a published threat model. Independent review remains tracked in stacksjs/stacks#2061. This RFC remains Proposed through the public review window ending 2026-08-20; implementation does not imply acceptance.