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58 lines
1.7 KiB
Markdown
58 lines
1.7 KiB
Markdown
# sha1cd
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A Go implementation of SHA1 with counter-cryptanalysis, which detects
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collision attacks.
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The `cgo/lib` code is a carbon copy of the [original code], based on
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the award winning [white paper] by Marc Stevens.
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The Go implementation is largely based off Go's generic sha1.
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At present no SIMD optimisations have been implemented.
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## Usage
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`sha1cd` can be used as a drop-in replacement for `crypto/sha1`:
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```golang
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import "github.com/pjbgf/sha1cd"
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func test(){
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data := []byte("data to be sha1 hashed")
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h := sha1cd.Sum(data)
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fmt.Printf("hash: %q\n", hex.EncodeToString(h))
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}
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```
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To obtain information as to whether a collision was found, use the
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func `CollisionResistantSum`.
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```golang
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import "github.com/pjbgf/sha1cd"
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func test(){
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data := []byte("data to be sha1 hashed")
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h, col := sha1cd.CollisionResistantSum(data)
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if col {
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fmt.Println("collision found!")
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}
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fmt.Printf("hash: %q", hex.EncodeToString(h))
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}
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```
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Note that the algorithm will automatically avoid collision, by
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extending the SHA1 to 240-steps, instead of 80 when a collision
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attempt is detected. Therefore, inputs that contains the unavoidable
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bit conditions will yield a different hash from `sha1cd`, when compared
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with results using `crypto/sha1`. Valid inputs will have matching the outputs.
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## References
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- https://shattered.io/
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- https://github.com/cr-marcstevens/sha1collisiondetection
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- https://csrc.nist.gov/Projects/Cryptographic-Algorithm-Validation-Program/Secure-Hashing#shavs
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## Use of the Original Implementation
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- https://github.com/git/git/commit/28dc98e343ca4eb370a29ceec4c19beac9b5c01e
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- https://github.com/libgit2/libgit2/pull/4136
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[original code]: https://github.com/cr-marcstevens/sha1collisiondetection
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[white paper]: https://marc-stevens.nl/research/papers/C13-S.pdf
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