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x/crypto/blake2s: add 224bit variant #36429

Open cathugger opened 4 years ago

cathugger commented 4 years ago

What version of Go are you using (go version)?

irrelevant

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

irrelevant

What did you do?

Went to https://godoc.org/golang.org/x/crypto/blake2s and looked for 224bit version.

What did you expect to see?

Something like func New224(key []byte) (hash.Hash, error) (kinda like in crypto/sha256) or func New(size int, key []byte) (hash.Hash, error) (like in x/crypto/blake2b).

What did you see instead?

I didn't find anything what would clearly enable using canonical blake2s-224 hash. Truncating New256 output would be ugly and wouldn't match canonical blake2s-224 (output size is embedded into IV). I don't think blake2s XOF would provide canonical blake2s-224 either.

toothrot commented 4 years ago

/cc @FiloSottile @katiehockman

cathugger commented 4 years ago

btw I can provide patch if needed, just not exactly sure about desired API. It'll probably be func New(size int, key []byte) (hash.Hash, error) as that'd mirror blake2b's API, and allow more choices blake2s is capable of. I'm unsure if Sum()-like API should be added, blake2b have them fixed-length without 224bit variant, and sha3's ShakeSum128/ShakeSum256 functions don't actually have output length distinguishers, so it wouldn't act exactly the same.

Nephirus commented 4 years ago

I've created a pull request for this issue, using API suggestion by @cathugger

https://github.com/golang/crypto/pull/147