Trait elliptic_curve::hash2curve::GroupDigest

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pub trait GroupDigest: CurveArithmeticwhere
    ProjectivePoint<Self>: CofactorGroup,{
    type FieldElement: FromOkm + MapToCurve<Output = ProjectivePoint<Self>> + Default + Copy;

    // Provided methods
    fn hash_from_bytes<'a, X: ExpandMsg<'a>>(
        msgs: &[&[u8]],
        dsts: &'a [&'a [u8]]
    ) -> Result<ProjectivePoint<Self>> { ... }
    fn encode_from_bytes<'a, X: ExpandMsg<'a>>(
        msgs: &[&[u8]],
        dsts: &'a [&'a [u8]]
    ) -> Result<ProjectivePoint<Self>> { ... }
    fn hash_to_scalar<'a, X: ExpandMsg<'a>>(
        msgs: &[&[u8]],
        dsts: &'a [&'a [u8]]
    ) -> Result<Self::Scalar>
       where Self::Scalar: FromOkm { ... }
}
Available on crate feature hash2curve only.
Expand description

Adds hashing arbitrary byte sequences to a valid group element

Required Associated Types§

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type FieldElement: FromOkm + MapToCurve<Output = ProjectivePoint<Self>> + Default + Copy

The field element representation for a group value with multiple elements

Provided Methods§

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fn hash_from_bytes<'a, X: ExpandMsg<'a>>( msgs: &[&[u8]], dsts: &'a [&'a [u8]] ) -> Result<ProjectivePoint<Self>>

Computes the hash to curve routine.

From https://www.ietf.org/archive/id/draft-irtf-cfrg-hash-to-curve-13.html:

Uniform encoding from byte strings to points in G. That is, the distribution of its output is statistically close to uniform in G. This function is suitable for most applications requiring a random oracle returning points in G assuming a cryptographically secure hash function is used.

Examples
Using a fixed size hash function
ⓘ
let pt = ProjectivePoint::hash_from_bytes::<ExpandMsgXmd<sha2::Sha256>>(b"test data", b"CURVE_XMD:SHA-256_SSWU_RO_");
Using an extendable output function
ⓘ
let pt = ProjectivePoint::hash_from_bytes::<ExpandMsgXof<sha3::Shake256>>(b"test data", b"CURVE_XOF:SHAKE-256_SSWU_RO_");
Errors

See implementors of ExpandMsg for errors:

len_in_bytes = <Self::FieldElement as FromOkm>::Length * 2

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fn encode_from_bytes<'a, X: ExpandMsg<'a>>( msgs: &[&[u8]], dsts: &'a [&'a [u8]] ) -> Result<ProjectivePoint<Self>>

Computes the encode to curve routine.

From https://www.ietf.org/archive/id/draft-irtf-cfrg-hash-to-curve-13.html:

Nonuniform encoding from byte strings to points in G. That is, the distribution of its output is not uniformly random in G: the set of possible outputs of encode_to_curve is only a fraction of the points in G, and some points in this set are more likely to be output than others.

Errors

See implementors of ExpandMsg for errors:

len_in_bytes = <Self::FieldElement as FromOkm>::Length

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fn hash_to_scalar<'a, X: ExpandMsg<'a>>( msgs: &[&[u8]], dsts: &'a [&'a [u8]] ) -> Result<Self::Scalar>where Self::Scalar: FromOkm,

Computes the hash to field routine according to https://www.ietf.org/archive/id/draft-irtf-cfrg-hash-to-curve-13.html#section-5 and returns a scalar.

Errors

See implementors of ExpandMsg for errors:

len_in_bytes = <Self::Scalar as FromOkm>::Length

Object Safety§

This trait is not object safe.

Implementors§