carbs

The problem. On the XRP Ledger a key has all the authority of an account or none, and a public key that has signed once stays visible on the ledger forever: a forgery target for a future quantum computer.

carbs puts three pieces together:

1. Signing sessions enforced by the ledger. A rippled amendment, SigningSessions, lets an account open a short-lived key (at most 10 minutes) that signs without prompting, bounded by the ledger itself. Mode A: every delegable transaction type except an exclusion list. Mode P: a list of XLS-75 permissions. Mode C: direct XRP payments under a total cap, fees included. A session key can never change who controls the account. A session is opened with one ordinary signature, from a Ledger device that shows the rules on its screen, or from a passkey.
2. A post-quantum root on a Ledger Stax. An ML-DSA-44 key held by the device clear-signs XRPL transactions, so an account can move its regular key to it and disable its classical master key.
3. A quantum exposure check and a guided migration for any XRPL account: is its public key already on the ledger, which other authorities expose keys, and what the move to a post-quantum key looks like.

Status of this first submission. The specification, the architecture and the decision records are written. The two upstream bases (XRPLF/rippled alphanet and LedgerHQ/app-xrp) are imported unmodified in their own commits. Every protocol code of the amendment is verified free on the imported tree and on the public AlphaNet. The test baselines of the imported tree are recorded. Clear signing of the session transactions and the ML-DSA root key are in progress on the device side. Next: the amendment itself, test first, following rippled's conventions.