Longeron Sign & Seal
Electronic signatures built for aviation records
Inspection reports, scrap logs, and quality forms sealed with standards-based digital signatures, independent timestamps, and an append-only audit trail — designed to align with the acceptance criteria in FAA Advisory Circular 120-78B.
Holding a Longeron-sealed document? Enter its certificate ID to verify it — no account needed.
How every sealed document is protected
Open, verifiable standards — not proprietary claims. Each guarantee below can be independently checked by your inspectors, your customers, or their regulators.
Cryptographic digital signature
Every sealed document carries a PAdES digital signature (the ISO 32000 / ETSI standard used across regulated industries). Open it in any standard PDF reader — Adobe Acrobat validates the seal and flags any modification made after signing.
Independent trusted timestamp
Each seal is countersigned by an RFC 3161 timestamp authority — an independent third party attesting to exactly when the document was sealed. The signing time can't be backdated, even by us.
Certificate ID on every document
Every sealed record is issued a unique certificate ID, printed on the document itself. Anyone holding the document can confirm its authenticity on our public verification page — no account required.
Tamper evidence by construction
The signature is computed over a SHA-256 digest of the exact file. Change one character — one pixel — and verification fails. What was signed is what you hold.
Original and sealed copies retained
The as-submitted original and the sealed output are both archived against the record, so the pre-signature source is always available for comparison and audit.
Append-only audit trail
Every signing event — including rejected attempts and verification views — is written to an append-only audit log with the signer, timestamp, and how the signer was authenticated. Log entries are never edited or deleted.
Alignment with FAA AC 120-78B
AC 120-78B describes what makes an electronic signature acceptable for aviation maintenance and inspection records. Here is how Sign & Seal addresses each criterion.
Uniqueness — the signature identifies one specific individual
Each seal names its individual signer — name, role, and inspector stamp number where assigned. Signing authority is provisioned against the customer organization's Microsoft Entra ID employee directory: if a person is not an active member of the directory, they cannot sign.
Significance & intent — signing is a deliberate act
A seal is never applied implicitly. The signer must complete an explicit attestation — affirmatively acknowledging what they are signing and that they are authorized to sign it — at the moment of sealing. The attestation text is stored with the record.
Scope — it is clear what is being attested
The signature is cryptographically bound to the exact document version via its SHA-256 digest, and the record stores the document type and reference. There is no ambiguity about which content the attestation covers.
Signer authentication
The signer's identity is verified server-side at the time of signing, and the authentication method used is recorded on every signing event — the record states not just who signed, but how we knew it was them.
Non-repudiation
The PAdES signature, the independent RFC 3161 timestamp, the stored attestation, and the audit trail together make a sealed record that cannot plausibly be denied later — and any third party can confirm it via the public certificate lookup.
Traceability & record integrity
Post-signature modification is detectable in any standard PDF reader. The append-only audit log preserves the full event history of each record, and the original unsealed document is retained alongside the sealed copy.
Retention & retrievability
Sealed records, their originals, attestations, and audit history are retained together and retrievable on demand by certificate ID — supporting the record-retention procedures your certificate or quality system requires.
A note on what “compliance” means here
The FAA does not approve or certify electronic-signature products. AC 120-78B provides acceptance guidance: each certificate holder adopts its own electronic-signature and recordkeeping procedures, typically coordinated with its principal inspector. Longeron Sign & Seal is designed so those procedures can be built on it and satisfy the AC’s criteria — we supply the signature mechanics, the verification chain, and the audit evidence; your quality system supplies the procedure. We’re happy to support that conversation with your PI or auditor.
Bring verifiable signatures to your quality records
Sign & Seal is part of the Longeron platform for aviation parts companies and repair stations — alongside photo QC, filing, and quoting.