sanad-verify 0.1.0

Offline verification library for Sanad Sign attestations — Ed25519 + CycloneDX + SHA-256 hash chain. India's sovereign attestation rail.

sanad-verify (Python)

Offline verification library for Sanad Sign attestations. Byte-for-byte compatible with the reference Node SDK — a signature produced by @cognoshift/sanad-sbom verifies here, and vice versa.

Built for CERT-In empanelled auditors, security reviewers, regulators, and internal compliance teams who live in Python.

Install

pip install sanad-verify

Only runtime dependency: cryptography. Supports Python 3.9+.

Verify a single attestation

import requests
from sanad_verify import verify_attestation

row = requests.get("https://sanad.cognoshift.in/api/sign/registry/<id>").json()

result = verify_attestation({
    "sbom":       row["sbom"],
    "signature":  row["signature"],
    "public_key": row["public_key"],
    "sbom_hash":  row["sbom_hash"],   # optional — recomputed regardless
})

print(result["valid"])            # True / False
print(result["signature_valid"])  # Ed25519 check
print(result["hash_match"])       # claimed vs recomputed SHA-256
print(result["computed_hash"])    # 'a3f5…'

Replay the hash chain

Given all attestations for a tenant (ordered ascending by created_at, id):

from sanad_verify import verify_chain

result = verify_chain(rows)

print(result["valid"])           # True when chain is intact
print(result["break_at"])        # id of first broken row, or None
print(result["first_mismatch"])  # detailed diagnostic

The genesis constant is SANAD_SIGN_GENESIS_2026 (exported as GENESIS). For a private deployment with a different genesis:

verify_chain(rows, genesis="MY_PRIVATE_GENESIS")

How verification works

1. Canonicalize the SBOM — recursive sort of object keys, arrays preserve order, compact separators, UTF-8 preserved. Matches the subset of RFC 8785 JCS that CycloneDX exercises.
2. Hash the canonical string with SHA-256. This is the sbom_hash.
3. Verify the Ed25519 signature over the hex-encoded sbom_hash, using the public key stored on the row (SPKI format, base64-decoded from DER).
4. Chain replay: for every row in the tenant's ledger, recompute SHA-256(event_hash || previous_chain_hash) and match against the stored chain_hash. previous_chain_hash is GENESIS for the first entry.

All four steps are deterministic. This library and the Node reference implementation produce identical output; either can verify attestations signed by the other.

Typing

The package ships a py.typed marker, so mypy / pyright / pylance pick up the full function signatures automatically.

License

Apache-2.0 — free for commercial audit use.