ecdsa: remove OutputSize bounds on DigestPrimitive#774
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Notably for curves like P-521, the digest used to compute the signature is smaller than a serialized field element (SHA-512 w\ 64-byte output vs 66-byte serialized field elements). To support such curves, we need to remove this bound. The already implemented `bits2field` function as defined in RFC6979 § 2.3.2 and SEC1 § 2.3.8 handles producing a serialized field element from an input which may be a different size.
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Now that RustCrypto/signatures#773 and RustCrypto/signatures#774 have landed it should be possible to use the upstream RFC6979 implementation from the `ecdsa` crate in conjunction with `p521`, which uses a Digest with a 64-byte output, but uses 66-byte field elements. However, we're currently failing to match RFC6979 test vectors.
tarcieri
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Now that RustCrypto/signatures#773 and RustCrypto/signatures#774 have landed it should be possible to use the upstream RFC6979 implementation from the `ecdsa` crate in conjunction with `p521`, which uses a Digest with a 64-byte output, but uses 66-byte field elements. However, we're currently failing to match RFC6979 test vectors.
tarcieri
added a commit
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that referenced
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Jan 17, 2024
Now that RustCrypto/signatures#773 and RustCrypto/signatures#774 have landed it should be possible to use the upstream RFC6979 implementation from the `ecdsa` crate in conjunction with `p521`, which uses a Digest with a 64-byte output, but uses 66-byte field elements.
tarcieri
added a commit
to RustCrypto/elliptic-curves
that referenced
this pull request
Jan 17, 2024
Now that RustCrypto/signatures#773 and RustCrypto/signatures#774 have landed it should be possible to use the upstream RFC6979 implementation from the `ecdsa` crate in conjunction with `p521`, which uses a Digest with a 64-byte output, but uses 66-byte field elements.
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Notably for curves like P-521, the digest used to compute the signature is smaller than a serialized field element (SHA-512 w\ 64-byte output vs 66-byte serialized field elements).
To support such curves, we need to remove this bound.
The already implemented
bits2fieldfunction as defined in RFC6979 § 2.3.2 and SEC1 § 2.3.8 handles producing a serialized field element from an input which may be a different size.