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Technical Team/SDPX 2.0 Provenance
It is desirable to be able to know the provenance of SPDX data. This means being able to reliably know who declared what SPDX information when, and where applicable, for what reason.
Components of SPDX Provenance include
- Signing of SPDX Data
SPDX Data Signing
Since SPDX Data can be represented in both RDF and Tag, and since there is no standard mechanism for signing RDF or Tag data as such (as there is in DSig for XML), we are left to fall back to signing the octets of the file containing that SPDX data. This has a few implications:
- The signature must be a in a separate file from the SPDX file (Example: foo.spdx has foo.spdx.sig containing it's signature)
- The SPDX file, once signed, must not be changed by downstream consumers of the file (because to change its octets would be to invalidate the signature).
SPDX Signing Proposal
SPDX files should optionally be signed using RFC 2440 PGP ascii-armored detached signatures.
Sign a file with GPG
sjc-vpn2-814:~ hagbard$ gpg --armor --output example.txt.sig --detach-sig example.txt
You need a passphrase to unlock the secret key for user: "Ed Warnicke " 1024-bit DSA key, ID 9AB88650, created 2001-09-09
See signature file
sjc-vpn2-814:~ hagbard$ cat example.txt.sig -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.17 (Darwin) Comment: GPGTools - http://gpgtools.org iEYEABECAAYFAk9NCpUACgkQpqzn7Jq4hlA3cACfUOxrlkISMjjLELGlLQuNn93h X6wAniliWFVoi7qfRGI79hwdLhajKcdI =0NsF -----END PGP SIGNATURE-----
Verify file with GPG
sjc-vpn2-814:~ hagbard$ gpg --verify example.txt.sig example.txt gpg: Signature made Tue Feb 28 11:10:45 2012 CST using DSA key ID 9AB88650 gpg: Good signature from "Ed Warnicke " gpg: aka "Ed Warnicke " Primary key fingerprint: 0B87 BC4A F6BF F571 FF9B BF51 A6AC E7EC 9AB8 8650
GPG is available for Linux, Mac, and Windows and provides PGP support. PGP support is available via the Legion of the Bouncy Castle in Java, and they provide an example DetachedSignatureProcessor in their openpgp examples section.