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* impl H2G for TE curves Co-authored-by: Alex Xiong <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,81 @@ | ||
| // Copyright (c) 2022 Espresso Systems (espressosys.com) | ||
| // This file is part of the Jellyfish library. | ||
|
|
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| // You should have received a copy of the MIT License | ||
| // along with the Jellyfish library. If not, see <https://mit-license.org/>. | ||
|
|
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| //! Hash to Elliptic Curve implementation of <https://datatracker.ietf.org/doc/draft-irtf-cfrg-hash-to-curve/> | ||
| use crate::errors::PrimitivesError; | ||
| use ark_ec::{ | ||
| short_weierstrass_jacobian::{GroupAffine, GroupProjective}, | ||
| AffineCurve, SWModelParameters, | ||
| }; | ||
| use ark_std::{ | ||
| rand::{Rng, SeedableRng}, | ||
| UniformRand, | ||
| }; | ||
| use digest::Digest; | ||
| use rand_chacha::ChaCha20Rng; | ||
| use sha2::Sha256; | ||
|
|
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| /// Trait definition and default implementation for hash to group functions for | ||
| /// Short Weierstrass Curves. | ||
| pub trait SWHashToGroup: SWModelParameters + Sized { | ||
| /// Hash to Group point, using sha2-512 function | ||
| /// hashing to G1 point of `C: ProjectiveCurve`. | ||
| // Default implementation implements a naive solution via rejection sampling. | ||
| // Slow, and non-constant time. | ||
| // | ||
| // For specific curves we may want to overload it with a more efficient | ||
| // algorithm, such as IETF BLS draft. | ||
| fn hash_to_group<B: AsRef<[u8]>>( | ||
| data: B, | ||
| cs_id: B, | ||
| ) -> Result<GroupProjective<Self>, PrimitivesError> { | ||
| let mut hasher = Sha256::new(); | ||
| hasher.update([cs_id.as_ref(), data.as_ref()].concat()); | ||
| let mut seed = [0u8; 32]; | ||
| seed.copy_from_slice(hasher.finalize().as_ref()); | ||
| let mut rng = ChaCha20Rng::from_seed(seed); | ||
| loop { | ||
| let x = Self::BaseField::rand(&mut rng); | ||
| // a boolean flag to decide if y is positive or not | ||
| let y_flag = rng.gen(); | ||
| if let Some(p) = GroupAffine::<Self>::get_point_from_x(x, y_flag) { | ||
| return Ok(p.mul_by_cofactor_to_projective()); | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl SWHashToGroup for ark_bls12_381::g1::Parameters { | ||
| // TODO: | ||
| // overload hash to group with the method in | ||
| // <https://github.com/algorand/pairing-plus/blob/7ec2ae03aae4ba2fc5210810211478171ccededf/src/bls12_381/osswu_map/g1.rs#L47> | ||
| } | ||
|
|
||
| impl SWHashToGroup for ark_bls12_377::g1::Parameters { | ||
| // TODO: | ||
| // overload hash to group with the method in | ||
| // <https://github.com/algorand/pairing-plus/blob/7ec2ae03aae4ba2fc5210810211478171ccededf/src/bls12_381/osswu_map/g1.rs#L47> | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| mod test { | ||
| use super::*; | ||
| use ark_std::vec; | ||
|
|
||
| #[test] | ||
| fn test_hash_to_group() { | ||
| test_hash_to_group_helper::<ark_bls12_381::g1::Parameters>(); | ||
| test_hash_to_group_helper::<ark_bls12_377::g1::Parameters>(); | ||
| } | ||
|
|
||
| fn test_hash_to_group_helper<P: SWHashToGroup>() { | ||
| let data = vec![1u8, 2, 3, 4, 5]; | ||
| let _g1 = | ||
| <P as SWHashToGroup>::hash_to_group::<&[u8]>(data.as_ref(), "bls signature".as_ref()) | ||
| .unwrap(); | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,81 @@ | ||
| // Copyright (c) 2022 Espresso Systems (espressosys.com) | ||
| // This file is part of the Jellyfish library. | ||
|
|
||
| // You should have received a copy of the MIT License | ||
| // along with the Jellyfish library. If not, see <https://mit-license.org/>. | ||
|
|
||
| //! Hash to Elliptic Curve implementation of <https://datatracker.ietf.org/doc/draft-irtf-cfrg-hash-to-curve/> | ||
| use crate::errors::PrimitivesError; | ||
| use ark_ec::{ | ||
| twisted_edwards_extended::{GroupAffine, GroupProjective}, | ||
| AffineCurve, TEModelParameters, | ||
| }; | ||
| use ark_std::{ | ||
| rand::{Rng, SeedableRng}, | ||
| UniformRand, | ||
| }; | ||
| use digest::Digest; | ||
| use rand_chacha::ChaCha20Rng; | ||
| use sha2::Sha256; | ||
|
|
||
| /// Trait definition and default implementation for hash to group functions for | ||
| /// Twisted Edwards Curves. | ||
| pub trait TEHashToGroup: TEModelParameters + Sized { | ||
| /// Hash to Group point, using sha2-512 function | ||
| /// hashing to G1 point of `C: ProjectiveCurve`. | ||
| // Default implementation implements a naive solution via rejection sampling. | ||
| // Slow, and non-constant time. | ||
| // | ||
| // For specific curves we may want to overload it with a more efficient | ||
| // algorithm, such as IETF BLS draft. | ||
| fn hash_to_group<B: AsRef<[u8]>>( | ||
| data: B, | ||
| cs_id: B, | ||
| ) -> Result<GroupProjective<Self>, PrimitivesError> { | ||
| let mut hasher = Sha256::new(); | ||
| hasher.update([cs_id.as_ref(), data.as_ref()].concat()); | ||
| let mut seed = [0u8; 32]; | ||
| seed.copy_from_slice(hasher.finalize().as_ref()); | ||
| let mut rng = ChaCha20Rng::from_seed(seed); | ||
| loop { | ||
| let x = Self::BaseField::rand(&mut rng); | ||
| // a boolean flag to decide if y is positive or not | ||
| let y_flag = rng.gen(); | ||
| if let Some(p) = GroupAffine::<Self>::get_point_from_x(x, y_flag) { | ||
| return Ok(p.mul_by_cofactor_to_projective()); | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl TEHashToGroup for ark_ed_on_bls12_377::EdwardsParameters { | ||
| // TODO: | ||
| // overload hash to group with the method in | ||
| // <https://github.com/algorand/pairing-plus/blob/7ec2ae03aae4ba2fc5210810211478171ccededf/src/bls12_381/osswu_map/g1.rs#L47> | ||
| } | ||
|
|
||
| impl TEHashToGroup for ark_ed_on_bls12_381::EdwardsParameters { | ||
| // TODO: | ||
| // overload hash to group with the method in | ||
| // <https://github.com/algorand/pairing-plus/blob/7ec2ae03aae4ba2fc5210810211478171ccededf/src/bls12_381/osswu_map/g1.rs#L47> | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| mod test { | ||
| use super::*; | ||
| use ark_std::vec; | ||
|
|
||
| #[test] | ||
| fn test_hash_to_group() { | ||
| test_hash_to_group_helper::<ark_ed_on_bls12_377::EdwardsParameters>(); | ||
| test_hash_to_group_helper::<ark_ed_on_bls12_381::EdwardsParameters>(); | ||
| } | ||
|
|
||
| fn test_hash_to_group_helper<P: TEHashToGroup>() { | ||
| let data = vec![1u8, 2, 3, 4, 5]; | ||
| let _g1 = | ||
| <P as TEHashToGroup>::hash_to_group::<&[u8]>(data.as_ref(), "Jubjub curves".as_ref()) | ||
| .unwrap(); | ||
| } | ||
| } |
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