Prove a field was there — without showing it
From a sealed dataset, hand an auditor a redacted exportwhere a sensitive column (a card PAN, an ID number, a medical field) is masked by a per-cell salted commitment. Using only the archive’s published seal, anyone can verify the masked column was present, every masked cell commits to a real value, and the disclosed columns are byte-identicalto the original — all without revealing the masked values and without re-sealing. It is the disclosure-with-proof sibling of erasure: the published Merkle root is invariant under the privacy op.
- same root
- a redacted export verifies to the ORIGINAL seal — no re-sealing
- O(log n)
- selectively open one cell to prove a real value, nothing else
- per-cell salt
- two equal PANs get distinct commitments — no leaked equality
- SHA-256 only
- verify with no account, no binary, no our-software
Seal it, redact it, prove it
at1 disclose seal pci.csv -o orders --subject-field order_id # sealed 5000 rows, 4 cols; sealed_root=4771e582... (published once) at1 disclose export orders --mask PAN -o redacted.json # redacted export -> redacted.json (masked ['PAN']); self-verify: OK at1 disclose verify-disclosure orders.seal.json redacted.json # PASS: redacted export verifies to the original seal # -> disclosed columns byte-identical; PAN present-but-masked at1 disclose open-cell orders redacted.json --row 2 --col PAN # PASS: cell (2,3) opens to a real committed value = '3400...0009'
Integrity is unconditional
Presence, byte-exactness of disclosed cells, and “this masked cell is not fabricated” hold against any adversary given the seal. Fabricate a commitment and the root breaks; lie on an open and the commitment breaks.
Salt custody = hiding
A 16-digit PAN is low-entropy, so each cell gets a fresh 32-byte salt kept in an erasable vault. Two equal PANs commit differently, so a redacted export leaks no join key. Confidentiality is exactly as strong as salt secrecy — we say so plainly.
The mirror of erasure
Erasure keeps the seal valid while destroying a subject’s key; disclosure keeps it valid while masking a field. Destroy a subject’s salts and their masked values become crypto-erased too — the root never moves.
Honest scope: integrity and presence are unconditional; hiding a masked value is exactly as strong as salt custody. Verification is free (SHA-256 only); issuing a disclosure export is the metered event.