- marked as enhancement
Support custom auth tag length
Issue #313
wontfix
Currently A256GCM encryption method produces only 128-bit auth tags.
It would be nice to have a possibility to customise its length.
Comments (3)
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reporter -
Are you aware that this would then no longer classify as A256GSM as specified in the JWA RFC?
https://tools.ietf.org/html/rfc7518#section-5.3
The requested size of the Authentication Tag output MUST be 128 bits, regardless of the key size.
And 128 bits is the longest value taken from the NIST spec:
https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38d.pdf
The bit length of the tag, denoted t, is a security parameter, as discussed in Appendix B. In general, t may be any one of the following five values: 128, 120, 112, 104, or 96.
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- changed status to wontfix
Customising the A256GSM auth tag length is against the spec.
If there's real need for that create a custom
enc
identifier and content encryption method. - Log in to comment