Ecosystem XLS: Qstamp Post Quantum Evidence Anchor Memo

[quantova-inc]

Category Ecosystem
Author Quantova Inc
Reference implementation https://github.com/quantova-inc/xrpl-pq-tooling

Abstract

A convention for writing a post quantum commitment to an off ledger record into an XRP Ledger transaction Memo, so that any third party can later prove the record existed in one exact form at a ledger close time, without the record itself reaching the ledger. No amendment is required.

Motivation

Banks, payment firms and AI agent operators need durable evidence that a record existed and was not altered, and regulators increasingly expect that evidence to remain sound against a future quantum computer. The XRP Ledger already carries Memos on every transaction type. Fixing one memo type lets wallets, explorers and auditors recognise a Qstamp anchor and verify it the same way everywhere.

Specification

For a record R, a 16 byte random salt s, the sending account A and a record kind K

fingerprint = SHA3-256(s || R)
commitment  = KECCAK-256(fingerprint || utf8(A) || 0x00 || utf8(K))

The commitment is written into one Memo on any valid transaction sent by A.

MemoType   = hex(ascii("qstamp/pq-evidence/1"))
MemoData   = hex(commitment)                       32 bytes, uppercase hex
MemoFormat = hex(ascii("application/vnd.qstamp.anchor"))

A reader recognises the anchor by MemoType and reads the 32 byte commitment from MemoData.

Verification

A verifier holding R, s, A and K recomputes the commitment and checks that a validated transaction from A carries a Qstamp Memo with that MemoData, at or before the ledger close time of interest.

Rationale

The commitment binds the fingerprint to the sending account and the record kind, so the same record anchored by two accounts yields two distinct commitments and one account cannot claim another's anchor. SHA3-256 and KECCAK-256 both retain about 128 bits of security against quantum search. The record stays off ledger, so no private data reaches the ledger and the cost is one Memo per anchor or per Merkle root of a batch.

Security considerations

The anchor proves existence and integrity at a time. It does not prove correctness of the record or authority to create it. Salting prevents a dictionary attack on low entropy records.

Reference implementation

The adapter in the linked repository builds the commitment and the Memo and reads it back, with tests for the round trip, uppercase hex encoding, account separation, rejection of foreign memos and rejection of a commitment of the wrong length. All tests pass. Quantova Inc also publishes the Qstamp post quantum SDK family on npm under the quantovainc organisation for issuing these anchors.