feat: add (de)compress trait in bls module (#22)

benches/kzg.rs

@@ -1,6 +1,7 @@
 use kateth::{
     blob::Blob,
-    kzg::{Bytes48, Setup},
+    kzg::{Commitment, Proof, Setup},
+    Compress,
 };
 
 use criterion::{criterion_group, criterion_main, BatchSize, BenchmarkId, Criterion, Throughput};
@@ -17,15 +18,19 @@ pub fn benchmark(c: &mut Criterion) {
     let blobs: Vec<Vec<u8>> = (0..max_batch_size)
         .map(|_| Blob::<4096>::random(&mut rng).to_bytes())
         .collect();
-    let commitments: Vec<Bytes48> = blobs
-        .iter()
-        .map(|blob| kzg.blob_to_commitment(blob).unwrap().serialize())
-        .collect();
-    let proofs: Vec<Bytes48> = blobs
-        .iter()
-        .zip(commitments.iter())
-        .map(|(blob, commitment)| kzg.blob_proof(blob, commitment).unwrap().serialize())
-        .collect();
+    let mut commitments = Vec::with_capacity(blobs.len());
+    let mut proofs = Vec::with_capacity(blobs.len());
+    for blob in &blobs {
+        let commitment = kzg.blob_to_commitment(blob).unwrap();
+        let mut bytes = [0u8; Commitment::COMPRESSED];
+        commitment.compress(&mut bytes).unwrap();
+        commitments.push(bytes);
+
+        let proof = kzg.blob_proof(blob, &bytes).unwrap();
+        let mut bytes = [0u8; Proof::COMPRESSED];
+        proof.compress(&mut bytes).unwrap();
+        proofs.push(bytes);
+    }
 
     c.bench_function("blob to kzg commitment", |b| {
         b.iter(|| kzg.blob_to_commitment(&blobs[0]))

src/blob.rs

@@ -1,5 +1,5 @@
 use crate::{
-    bls::{FiniteFieldError, Fr, P1},
+    bls::{Compress, FiniteFieldError, Fr, P1},
     kzg::{Commitment, Polynomial, Proof, Setup},
 };
 
@@ -79,7 +79,10 @@ impl<const N: usize> Blob<N> {
         const DOMAIN: &[u8; 16] = b"FSBLOBVERIFY_V1_";
         let degree = (N as u128).to_be_bytes();
 
-        let comm = commitment.serialize();
+        let mut comm = [0u8; Commitment::COMPRESSED];
+        commitment
+            .compress(comm.as_mut_slice())
+            .expect("sufficient buffer len");
 
         let mut data = Vec::with_capacity(8 + 16 + Commitment::BYTES + Self::BYTES);
         data.extend_from_slice(DOMAIN);

src/bls.rs

@@ -10,11 +10,12 @@ use blst::{
     blst_fr, blst_fr_add, blst_fr_cneg, blst_fr_eucl_inverse, blst_fr_from_scalar,
     blst_fr_from_uint64, blst_fr_lshift, blst_fr_mul, blst_fr_rshift, blst_fr_sub,
     blst_lendian_from_scalar, blst_miller_loop, blst_p1, blst_p1_add, blst_p1_affine,
-    blst_p1_affine_in_g1, blst_p1_cneg, blst_p1_compress, blst_p1_deserialize, blst_p1_from_affine,
-    blst_p1_mult, blst_p1_to_affine, blst_p2, blst_p2_add, blst_p2_affine, blst_p2_affine_in_g2,
-    blst_p2_deserialize, blst_p2_from_affine, blst_p2_mult, blst_p2_to_affine, blst_scalar,
-    blst_scalar_fr_check, blst_scalar_from_bendian, blst_scalar_from_fr, blst_sha256,
-    blst_uint64_from_fr, p1_affines, BLS12_381_G2, BLS12_381_NEG_G1, BLS12_381_NEG_G2, BLST_ERROR,
+    blst_p1_affine_in_g1, blst_p1_cneg, blst_p1_compress, blst_p1_from_affine, blst_p1_mult,
+    blst_p1_to_affine, blst_p1_uncompress, blst_p2, blst_p2_add, blst_p2_affine,
+    blst_p2_affine_in_g2, blst_p2_compress, blst_p2_from_affine, blst_p2_mult, blst_p2_to_affine,
+    blst_p2_uncompress, blst_scalar, blst_scalar_fr_check, blst_scalar_from_bendian,
+    blst_scalar_from_fr, blst_sha256, blst_uint64_from_fr, p1_affines, BLS12_381_G2,
+    BLS12_381_NEG_G1, BLS12_381_NEG_G2, BLST_ERROR,
 };
 
 #[derive(Clone, Copy, Debug)]
@@ -48,6 +49,32 @@ impl From<ECGroupError> for Error {
     }
 }
 
+/// A data structure that can be serialized into the compressed format defined by Zcash.
+///
+/// github.com/zkcrypto/pairing/blob/34aa52b0f7bef705917252ea63e5a13fa01af551/src/bls12_381/README.md
+pub trait Compress {
+    /// The length in bytes of the compressed representation of `self`.
+    const COMPRESSED: usize;
+
+    /// Compresses `self` into `buf`.
+    ///
+    /// # Errors
+    ///
+    /// Compression will fail if the length of `buf` is less than `Self::COMPRESSED`.
+    fn compress(&self, buf: impl AsMut<[u8]>) -> Result<(), &'static str>;
+}
+
+/// A data structure that can be deserialized from the compressed format defined by Zcash.
+///
+/// github.com/zkcrypto/pairing/blob/34aa52b0f7bef705917252ea63e5a13fa01af551/src/bls12_381/README.md
+pub trait Decompress: Sized {
+    /// The error that can occur upon decompression.
+    type Error;
+
+    /// Decompresses `compressed` into `Self`.
+    fn decompress(compressed: impl AsRef<[u8]>) -> Result<Self, Self::Error>;
+}
+
 #[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
 pub struct Fr {
     element: blst_fr,
@@ -355,37 +382,6 @@ impl P1 {
     pub const BITS: usize = 384;
     pub const BYTES: usize = Self::BITS / 8;
 
-    pub fn deserialize(bytes: &[u8; Self::BYTES]) -> Result<Self, ECGroupError> {
-        let mut affine = MaybeUninit::<blst_p1_affine>::uninit();
-        let mut out = MaybeUninit::<blst_p1>::uninit();
-        unsafe {
-            // NOTE: deserialize performs a curve check but not a subgroup check. if that changes,
-            // then we should encounter `unreachable` for `BLST_POINT_NOT_IN_GROUP` in tests.
-            match blst_p1_deserialize(affine.as_mut_ptr(), bytes.as_ptr()) {
-                BLST_ERROR::BLST_SUCCESS => {}
-                BLST_ERROR::BLST_BAD_ENCODING => return Err(ECGroupError::InvalidEncoding),
-                BLST_ERROR::BLST_POINT_NOT_ON_CURVE => return Err(ECGroupError::NotOnCurve),
-                other => unreachable!("{other:?}"),
-            }
-            if !blst_p1_affine_in_g1(affine.as_ptr()) {
-                return Err(ECGroupError::NotInGroup);
-            }
-
-            blst_p1_from_affine(out.as_mut_ptr(), affine.as_ptr());
-            Ok(Self {
-                element: out.assume_init(),
-            })
-        }
-    }
-
-    pub fn serialize(&self) -> [u8; Self::BYTES] {
-        let mut out = [0; Self::BYTES];
-        unsafe {
-            blst_p1_compress(out.as_mut_ptr(), &self.element);
-        }
-        out
-    }
-
     pub fn lincomb(points: impl AsRef<[Self]>, scalars: impl AsRef<[Fr]>) -> Self {
         let n = cmp::min(points.as_ref().len(), scalars.as_ref().len());
         let mut lincomb = Self::INF;
@@ -506,37 +502,55 @@ impl Neg for P1 {
     }
 }
 
-#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
-pub struct P2 {
-    element: blst_p2,
+impl Compress for P1 {
+    const COMPRESSED: usize = Self::BYTES;
+
+    fn compress(&self, mut buf: impl AsMut<[u8]>) -> Result<(), &'static str> {
+        if buf.as_mut().len() < Self::COMPRESSED {
+            return Err("insufficient buffer length");
+        }
+        unsafe {
+            blst_p1_compress(buf.as_mut().as_mut_ptr(), &self.element);
+        }
+        Ok(())
+    }
 }
 
-impl P2 {
-    pub const BITS: usize = 768;
-    pub const BYTES: usize = Self::BITS / 8;
+impl Decompress for P1 {
+    type Error = ECGroupError;
 
-    pub fn deserialize(bytes: &[u8; Self::BYTES]) -> Result<Self, ECGroupError> {
-        let mut affine = MaybeUninit::<blst_p2_affine>::uninit();
-        let mut out = MaybeUninit::<blst_p2>::uninit();
+    fn decompress(compressed: impl AsRef<[u8]>) -> Result<Self, Self::Error> {
+        let mut affine = MaybeUninit::<blst_p1_affine>::uninit();
+        let mut out = MaybeUninit::<blst_p1>::uninit();
         unsafe {
-            // NOTE: deserialize performs a curve check but not a subgroup check. if that changes,
+            // NOTE: uncompress performs a curve check but not a subgroup check. if that changes,
             // then we should encounter `unreachable` for `BLST_POINT_NOT_IN_GROUP` in tests.
-            match blst_p2_deserialize(affine.as_mut_ptr(), bytes.as_ref().as_ptr()) {
+            match blst_p1_uncompress(affine.as_mut_ptr(), compressed.as_ref().as_ptr()) {
                 BLST_ERROR::BLST_SUCCESS => {}
                 BLST_ERROR::BLST_BAD_ENCODING => return Err(ECGroupError::InvalidEncoding),
                 BLST_ERROR::BLST_POINT_NOT_ON_CURVE => return Err(ECGroupError::NotOnCurve),
                 other => unreachable!("{other:?}"),
             }
-            if !blst_p2_affine_in_g2(affine.as_ptr()) {
+            if !blst_p1_affine_in_g1(affine.as_ptr()) {
                 return Err(ECGroupError::NotInGroup);
             }
 
-            blst_p2_from_affine(out.as_mut_ptr(), affine.as_ptr());
+            blst_p1_from_affine(out.as_mut_ptr(), affine.as_ptr());
             Ok(Self {
                 element: out.assume_init(),
             })
         }
     }
+}
+
+#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
+pub struct P2 {
+    element: blst_p2,
+}
+
+impl P2 {
+    pub const BITS: usize = 768;
+    pub const BYTES: usize = Self::BITS / 8;
 
     // TODO: make available as `const`
     pub fn generator() -> Self {
@@ -608,6 +622,47 @@ impl Mul<Fr> for P2 {
     }
 }
 
+impl Compress for P2 {
+    const COMPRESSED: usize = Self::BYTES;
+
+    fn compress(&self, mut buf: impl AsMut<[u8]>) -> Result<(), &'static str> {
+        if buf.as_mut().len() < Self::COMPRESSED {
+            return Err("insufficient buffer length");
+        }
+        unsafe {
+            blst_p2_compress(buf.as_mut().as_mut_ptr(), &self.element);
+        }
+        Ok(())
+    }
+}
+
+impl Decompress for P2 {
+    type Error = ECGroupError;
+
+    fn decompress(compressed: impl AsRef<[u8]>) -> Result<Self, Self::Error> {
+        let mut affine = MaybeUninit::<blst_p2_affine>::uninit();
+        let mut out = MaybeUninit::<blst_p2>::uninit();
+        unsafe {
+            // NOTE: uncompress performs a curve check but not a subgroup check. if that changes,
+            // then we should encounter `unreachable` for `BLST_POINT_NOT_IN_GROUP` in tests.
+            match blst_p2_uncompress(affine.as_mut_ptr(), compressed.as_ref().as_ptr()) {
+                BLST_ERROR::BLST_SUCCESS => {}
+                BLST_ERROR::BLST_BAD_ENCODING => return Err(ECGroupError::InvalidEncoding),
+                BLST_ERROR::BLST_POINT_NOT_ON_CURVE => return Err(ECGroupError::NotOnCurve),
+                other => unreachable!("{other:?}"),
+            }
+            if !blst_p2_affine_in_g2(affine.as_ptr()) {
+                return Err(ECGroupError::NotInGroup);
+            }
+
+            blst_p2_from_affine(out.as_mut_ptr(), affine.as_ptr());
+            Ok(Self {
+                element: out.assume_init(),
+            })
+        }
+    }
+}
+
 pub fn verify_pairings((a1, a2): (P1, P2), (b1, b2): (P1, P2)) -> bool {
     let mut a1_neg_affine = MaybeUninit::<blst_p1_affine>::uninit();
     let mut a2_affine = MaybeUninit::<blst_p2_affine>::uninit();

src/kzg/setup.rs

@@ -7,7 +7,7 @@ use std::{
 use super::{Bytes32, Bytes48, Commitment, Error, Polynomial, Proof};
 use crate::{
     blob::{Blob, Error as BlobError},
-    bls::{self, ECGroupError, Error as BlsError, Fr, P1, P2},
+    bls::{self, Decompress, ECGroupError, Error as BlsError, Fr, P1, P2},
     math,
 };
 
@@ -60,7 +60,7 @@ impl<const G1: usize, const G2: usize> Setup<G1, G2> {
             // TODO: skip unnecessary allocation
             let point = FixedBytes::<48>::from_slice(point);
             let point =
-                P1::deserialize(&point).map_err(|err| LoadSetupError::Bls(BlsError::from(err)))?;
+                P1::decompress(point).map_err(|err| LoadSetupError::Bls(BlsError::from(err)))?;
             g1_lagrange[i] = point;
         }
         let g1_lagrange_brp = math::bit_reversal_permutation_boxed_array(g1_lagrange.as_slice());
@@ -75,7 +75,7 @@ impl<const G1: usize, const G2: usize> Setup<G1, G2> {
             // TODO: skip unnecessary allocation
             let point = FixedBytes::<96>::from_slice(point);
             let point =
-                P2::deserialize(&point).map_err(|err| LoadSetupError::Bls(BlsError::from(err)))?;
+                P2::decompress(point).map_err(|err| LoadSetupError::Bls(BlsError::from(err)))?;
             g2_monomial[i] = point;
         }
 
@@ -108,8 +108,8 @@ impl<const G1: usize, const G2: usize> Setup<G1, G2> {
         point: &Bytes32,
         eval: &Bytes32,
     ) -> Result<bool, Error> {
-        let proof = Proof::deserialize(proof).map_err(|err| Error::from(BlsError::ECGroup(err)))?;
-        let commitment = Commitment::deserialize(commitment)
+        let proof = Proof::decompress(proof).map_err(|err| Error::from(BlsError::ECGroup(err)))?;
+        let commitment = Commitment::decompress(commitment)
             .map_err(|err| Error::from(BlsError::ECGroup(err)))?;
         let point =
             Fr::from_be_slice(point).map_err(|err| Error::from(BlsError::FiniteField(err)))?;
@@ -184,7 +184,7 @@ impl<const G1: usize, const G2: usize> Setup<G1, G2> {
 
     pub fn blob_proof(&self, blob: impl AsRef<[u8]>, commitment: &Bytes48) -> Result<Proof, Error> {
         let blob: Blob<G1> = Blob::from_slice(blob).map_err(Error::from)?;
-        let commitment = Commitment::deserialize(commitment)
+        let commitment = Commitment::decompress(commitment)
             .map_err(|err| Error::from(BlsError::ECGroup(err)))?;
         let proof = self.blob_proof_inner(&blob, &commitment);
         Ok(proof)
@@ -220,9 +220,9 @@ impl<const G1: usize, const G2: usize> Setup<G1, G2> {
         proof: &Bytes48,
     ) -> Result<bool, Error> {
         let blob: Blob<G1> = Blob::from_slice(blob).map_err(Error::from)?;
-        let commitment = Commitment::deserialize(commitment)
+        let commitment = Commitment::decompress(commitment)
             .map_err(|err| Error::from(BlsError::ECGroup(err)))?;
-        let proof = Proof::deserialize(proof).map_err(|err| Error::from(BlsError::ECGroup(err)))?;
+        let proof = Proof::decompress(proof).map_err(|err| Error::from(BlsError::ECGroup(err)))?;
 
         let verified = self.verify_blob_proof_inner(&blob, &commitment, &proof);
         Ok(verified)
@@ -271,12 +271,11 @@ impl<const G1: usize, const G2: usize> Setup<G1, G2> {
         let commitments: Result<Vec<Commitment>, _> = commitments
             .as_ref()
             .iter()
-            .map(Commitment::deserialize)
+            .map(Commitment::decompress)
             .collect();
         let commitments = commitments.map_err(|err| Error::from(BlsError::ECGroup(err)))?;
 
-        let proofs: Result<Vec<Proof>, _> =
-            proofs.as_ref().iter().map(Proof::deserialize).collect();
+        let proofs: Result<Vec<Proof>, _> = proofs.as_ref().iter().map(Proof::decompress).collect();
         let proofs = proofs.map_err(|err| Error::from(BlsError::ECGroup(err)))?;
 
         let verified = self.verify_blob_proof_batch_inner(blobs, commitments, proofs);
@@ -288,9 +287,12 @@ impl<const G1: usize, const G2: usize> Setup<G1, G2> {
 mod tests {
     use super::*;
 
-    use crate::kzg::spec::{
-        BlobToCommitment, ComputeBlobProof, ComputeProof, VerifyBlobProof, VerifyBlobProofBatch,
-        VerifyProof,
+    use crate::{
+        bls::Compress,
+        kzg::spec::{
+            BlobToCommitment, ComputeBlobProof, ComputeProof, VerifyBlobProof,
+            VerifyBlobProofBatch, VerifyProof,
+        },
     };
 
     use std::{
@@ -343,7 +345,9 @@ mod tests {
                 continue;
             };
             let (expected_proof, expected_y) = expected.unwrap();
-            assert_eq!(proof.serialize(), expected_proof);
+            let mut proof_bytes = [0u8; Proof::COMPRESSED];
+            proof.compress(&mut proof_bytes).unwrap();
+            assert_eq!(proof_bytes, expected_proof);
             assert_eq!(y.to_be_bytes(), expected_y);
         }
     }
@@ -367,7 +371,9 @@ mod tests {
                 continue;
             };
             let expected = expected.unwrap();
-            assert_eq!(proof.serialize(), expected);
+            let mut proof_bytes = [0u8; Proof::COMPRESSED];
+            proof.compress(&mut proof_bytes).unwrap();
+            assert_eq!(proof_bytes, expected);
         }
     }
 
@@ -387,7 +393,9 @@ mod tests {
                 continue;
             };
             let expected = expected.unwrap();
-            assert_eq!(commitment.serialize(), expected);
+            let mut commitment_bytes = [0u8; Commitment::COMPRESSED];
+            commitment.compress(&mut commitment_bytes).unwrap();
+            assert_eq!(commitment_bytes, expected);
         }
     }
 

src/lib.rs

@@ -1,5 +1,6 @@
 mod bls;
 mod math;
 
+pub use bls::{Compress, Decompress};
 pub mod blob;
 pub mod kzg;