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bls.rs
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bls.rs
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//! BLS12-381 key support
use core::{
fmt::{self, Debug, Formatter},
ops::Add,
};
use aead::generic_array::GenericArray;
use blake2::Digest;
use bls12_381::{G1Affine, G1Projective, G2Affine, G2Projective, Scalar};
use group::GroupEncoding;
use sha2::Sha256;
use subtle::ConstantTimeEq;
use zeroize::{Zeroize, Zeroizing};
use crate::generic_array::{
typenum::{self, Unsigned, U144, U32, U48, U96},
ArrayLength,
};
use super::{BlsCurves, HasKeyAlg, KeyAlg};
use crate::{
buffer::ArrayKey,
error::Error,
jwk::{FromJwk, JwkEncoder, JwkParts, ToJwk},
random::KeyMaterial,
repr::{KeyGen, KeyMeta, KeyPublicBytes, KeySecretBytes, KeypairMeta},
};
/// The 'kty' value of a BLS key JWK
pub const JWK_KEY_TYPE: &str = "OKP";
/// A BLS12-381 key pair
#[derive(Clone, Zeroize)]
pub struct BlsKeyPair<Pk: BlsPublicKeyType> {
secret: Option<BlsSecretKey>,
public: Pk::Buffer,
}
impl<Pk: BlsPublicKeyType> BlsKeyPair<Pk> {
/// Generate a new BLS key from a seed according to the KeyGen algorithm
pub fn from_seed(seed: &[u8]) -> Result<Self, Error> {
Ok(Self::from_secret_key(BlsSecretKey::generate(
BlsKeyGen::new(seed)?,
)?))
}
#[inline]
pub(crate) fn from_secret_key(sk: BlsSecretKey) -> Self {
let public = Pk::from_secret_scalar(&sk.0);
Self {
secret: Some(sk),
public,
}
}
pub(crate) fn check_public_bytes(&self, pk: &[u8]) -> Result<(), Error> {
if Pk::with_bytes(&self.public, None, |slf| slf.ct_eq(pk)).into() {
Ok(())
} else {
Err(err_msg!(InvalidKeyData, "invalid BLS keypair"))
}
}
/// Accessor for the associated public key
pub fn bls_public_key(&self) -> &Pk::Buffer {
&self.public
}
/// Accessor for the associated secret key value, if any
pub fn bls_secret_scalar(&self) -> Option<&Scalar> {
self.secret.as_ref().map(|s| &s.0)
}
}
impl<Pk: BlsPublicKeyType> Debug for BlsKeyPair<Pk> {
fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
f.debug_struct("BlsKeyPair")
.field("crv", &Pk::JWK_CURVE)
.field("secret", &self.secret)
.field("public", &self.public)
.finish()
}
}
impl<Pk: BlsPublicKeyType> PartialEq for BlsKeyPair<Pk> {
fn eq(&self, other: &Self) -> bool {
other.secret == self.secret && other.public == self.public
}
}
impl<Pk: BlsPublicKeyType> Eq for BlsKeyPair<Pk> {}
impl<Pk: BlsPublicKeyType> HasKeyAlg for BlsKeyPair<Pk> {
fn algorithm(&self) -> KeyAlg {
KeyAlg::Bls12_381(Pk::ALG_TYPE)
}
}
impl<Pk: BlsPublicKeyType> KeyMeta for BlsKeyPair<Pk> {
type KeySize = U32;
}
impl<Pk> KeypairMeta for BlsKeyPair<Pk>
where
Pk: BlsPublicKeyType,
U32: Add<Pk::BufferSize>,
<U32 as Add<Pk::BufferSize>>::Output: ArrayLength<u8>,
{
type PublicKeySize = Pk::BufferSize;
type KeypairSize = typenum::Sum<Self::KeySize, Pk::BufferSize>;
}
impl<Pk: BlsPublicKeyType> KeyGen for BlsKeyPair<Pk> {
fn generate(rng: impl KeyMaterial) -> Result<Self, Error> {
let secret = BlsSecretKey::generate(rng)?;
Ok(Self::from_secret_key(secret))
}
}
impl<Pk: BlsPublicKeyType> KeySecretBytes for BlsKeyPair<Pk> {
fn from_secret_bytes(key: &[u8]) -> Result<Self, Error>
where
Self: Sized,
{
let sk = BlsSecretKey::from_bytes(key)?;
Ok(Self::from_secret_key(sk))
}
fn with_secret_bytes<O>(&self, f: impl FnOnce(Option<&[u8]>) -> O) -> O {
if let Some(sk) = self.secret.as_ref() {
let mut skb = Zeroizing::new(sk.0.to_bytes());
skb.reverse(); // into big-endian
f(Some(&*skb))
} else {
f(None)
}
}
}
impl<Pk: BlsPublicKeyType> KeyPublicBytes for BlsKeyPair<Pk>
where
Self: KeypairMeta,
{
fn from_public_bytes(key: &[u8]) -> Result<Self, Error> {
Ok(Self {
secret: None,
public: Pk::from_public_bytes(key)?,
})
}
fn with_public_bytes<O>(&self, f: impl FnOnce(&[u8]) -> O) -> O {
Pk::with_bytes(&self.public, None, f)
}
}
impl<Pk: BlsPublicKeyType> ToJwk for BlsKeyPair<Pk> {
fn encode_jwk(&self, enc: &mut dyn JwkEncoder) -> Result<(), Error> {
enc.add_str("crv", Pk::get_jwk_curve(enc.alg()))?;
enc.add_str("kty", JWK_KEY_TYPE)?;
Pk::with_bytes(&self.public, enc.alg(), |buf| enc.add_as_base64("x", buf))?;
if enc.is_secret() {
self.with_secret_bytes(|buf| {
if let Some(sk) = buf {
enc.add_as_base64("d", sk)
} else {
Ok(())
}
})?;
}
Ok(())
}
}
impl<Pk: BlsPublicKeyType> FromJwk for BlsKeyPair<Pk> {
fn from_jwk_parts(jwk: JwkParts<'_>) -> Result<Self, Error> {
if jwk.kty != JWK_KEY_TYPE &&
/* compatibility with previous version */
jwk.kty != "EC"
{
return Err(err_msg!(InvalidKeyData, "Unsupported key type"));
}
if jwk.crv != Pk::JWK_CURVE {
return Err(err_msg!(InvalidKeyData, "Unsupported key algorithm"));
}
ArrayKey::<Pk::BufferSize>::temp(|pk_arr| {
if jwk.x.decode_base64(pk_arr)? != pk_arr.len() {
Err(err_msg!(InvalidKeyData))
} else if jwk.d.is_some() {
ArrayKey::<U32>::temp(|sk_arr| {
if jwk.d.decode_base64(sk_arr)? != sk_arr.len() {
Err(err_msg!(InvalidKeyData))
} else {
let result = BlsKeyPair::from_secret_key(BlsSecretKey::from_bytes(sk_arr)?);
result.check_public_bytes(pk_arr)?;
Ok(result)
}
})
} else {
Ok(Self {
secret: None,
public: Pk::from_public_bytes(pk_arr)?,
})
}
})
}
}
#[derive(Clone, Debug, PartialEq, Eq, Zeroize)]
#[repr(transparent)]
pub(crate) struct BlsSecretKey(Scalar);
impl BlsSecretKey {
fn generate(mut rng: impl KeyMaterial) -> Result<Self, Error> {
let mut secret = Zeroizing::new([0u8; 64]);
rng.read_okm(&mut secret[16..]);
secret.reverse(); // into little endian
Ok(Self(Scalar::from_bytes_wide(&secret)))
}
pub fn from_bytes(sk: &[u8]) -> Result<Self, Error> {
if sk.len() != 32 {
return Err(err_msg!(InvalidKeyData));
}
let mut skb = Zeroizing::new([0u8; 32]);
skb.copy_from_slice(sk);
skb.reverse(); // into little endian
let result: Option<Scalar> = Scalar::from_bytes(&skb).into();
Ok(Self(result.ok_or_else(|| err_msg!(InvalidKeyData))?))
}
}
impl Drop for BlsSecretKey {
fn drop(&mut self) {
self.zeroize();
}
}
/// A key material generator compatible with KeyGen from the
/// bls-signatures RFC draft 4 (incompatible with earlier)
#[derive(Debug, Clone)]
pub struct BlsKeyGen<'g> {
salt: Option<GenericArray<u8, U32>>,
ikm: &'g [u8],
}
impl<'g> BlsKeyGen<'g> {
/// Construct a new `BlsKeyGen` from a seed value
pub fn new(ikm: &'g [u8]) -> Result<Self, Error> {
if ikm.len() < 32 {
return Err(err_msg!(Usage, "Insufficient length for seed"));
}
Ok(Self { salt: None, ikm })
}
}
impl KeyMaterial for BlsKeyGen<'_> {
fn read_okm(&mut self, buf: &mut [u8]) {
const SALT: &[u8] = b"BLS-SIG-KEYGEN-SALT-";
self.salt.replace(match self.salt {
None => Sha256::digest(SALT),
Some(salt) => Sha256::digest(salt),
});
let mut extract = hkdf::HkdfExtract::<Sha256>::new(Some(self.salt.as_ref().unwrap()));
extract.input_ikm(self.ikm);
extract.input_ikm(&[0u8]);
let (_, hkdf) = extract.finalize();
hkdf.expand(&(buf.len() as u16).to_be_bytes(), buf)
.expect("HDKF extract failure");
}
}
/// Trait implemented by supported BLS public key types
pub trait BlsPublicKeyType: 'static {
/// The concrete key representation
type Buffer: Clone + Debug + PartialEq + Sized + Zeroize;
/// The size of the serialized public key
type BufferSize: ArrayLength<u8>;
/// The associated algorithm type
const ALG_TYPE: BlsCurves;
/// The associated JWK curve name
const JWK_CURVE: &'static str;
/// Get the JWK curve for a specific key algorithm
fn get_jwk_curve(_alg: Option<KeyAlg>) -> &'static str {
Self::JWK_CURVE
}
/// Initialize from the secret scalar
fn from_secret_scalar(secret: &Scalar) -> Self::Buffer;
/// Initialize from the compressed bytes
fn from_public_bytes(key: &[u8]) -> Result<Self::Buffer, Error>;
/// Access the bytes of the public key
fn with_bytes<O>(buf: &Self::Buffer, alg: Option<KeyAlg>, f: impl FnOnce(&[u8]) -> O) -> O;
}
/// G1 curve
#[derive(Debug)]
pub struct G1;
impl BlsPublicKeyType for G1 {
type Buffer = G1Affine;
type BufferSize = U48;
const ALG_TYPE: BlsCurves = BlsCurves::G1;
const JWK_CURVE: &'static str = "BLS12381_G1";
#[inline]
fn from_secret_scalar(secret: &Scalar) -> Self::Buffer {
G1Affine::from(G1Projective::generator() * secret)
}
fn from_public_bytes(key: &[u8]) -> Result<Self::Buffer, Error> {
let buf: Option<G1Affine> = G1Affine::from_compressed(
TryInto::<&[u8; 48]>::try_into(key).map_err(|_| err_msg!(InvalidKeyData))?,
)
.into();
buf.ok_or_else(|| err_msg!(InvalidKeyData))
}
fn with_bytes<O>(buf: &Self::Buffer, _alg: Option<KeyAlg>, f: impl FnOnce(&[u8]) -> O) -> O {
f(buf.to_bytes().as_ref())
}
}
/// G2 curve
#[derive(Debug)]
pub struct G2;
impl BlsPublicKeyType for G2 {
type Buffer = G2Affine;
type BufferSize = U96;
const ALG_TYPE: BlsCurves = BlsCurves::G2;
const JWK_CURVE: &'static str = "BLS12381_G2";
#[inline]
fn from_secret_scalar(secret: &Scalar) -> Self::Buffer {
G2Affine::from(G2Projective::generator() * secret)
}
fn from_public_bytes(key: &[u8]) -> Result<Self::Buffer, Error> {
let buf: Option<G2Affine> = G2Affine::from_compressed(
TryInto::<&[u8; 96]>::try_into(key).map_err(|_| err_msg!(InvalidKeyData))?,
)
.into();
buf.ok_or_else(|| err_msg!(InvalidKeyData))
}
fn with_bytes<O>(buf: &Self::Buffer, _alg: Option<KeyAlg>, f: impl FnOnce(&[u8]) -> O) -> O {
f(buf.to_bytes().as_ref())
}
}
/// G1 + G2 curves
#[derive(Debug)]
pub struct G1G2;
impl BlsPublicKeyType for G1G2 {
type Buffer = G1G2Pair;
type BufferSize = U144;
const ALG_TYPE: BlsCurves = BlsCurves::G1G2;
const JWK_CURVE: &'static str = "BLS12381_G1G2";
fn get_jwk_curve(alg: Option<KeyAlg>) -> &'static str {
if alg == Some(KeyAlg::Bls12_381(BlsCurves::G1)) {
G1::JWK_CURVE
} else if alg == Some(KeyAlg::Bls12_381(BlsCurves::G2)) {
G2::JWK_CURVE
} else {
Self::JWK_CURVE
}
}
#[inline]
fn from_secret_scalar(secret: &Scalar) -> Self::Buffer {
G1G2Pair(
G1Affine::from(G1Projective::generator() * secret),
G2Affine::from(G2Projective::generator() * secret),
)
}
fn from_public_bytes(key: &[u8]) -> Result<Self::Buffer, Error> {
if key.len() != Self::BufferSize::USIZE {
return Err(err_msg!(InvalidKeyData));
}
let g1: Option<G1Affine> =
G1Affine::from_compressed(TryInto::<&[u8; 48]>::try_into(&key[..48]).unwrap()).into();
let g2: Option<G2Affine> =
G2Affine::from_compressed(TryInto::<&[u8; 96]>::try_into(&key[48..]).unwrap()).into();
if let (Some(g1), Some(g2)) = (g1, g2) {
Ok(G1G2Pair(g1, g2))
} else {
Err(err_msg!(InvalidKeyData))
}
}
fn with_bytes<O>(buf: &Self::Buffer, alg: Option<KeyAlg>, f: impl FnOnce(&[u8]) -> O) -> O {
if alg == Some(KeyAlg::Bls12_381(BlsCurves::G1)) {
ArrayKey::<U48>::temp(|arr| {
arr.copy_from_slice(buf.0.to_bytes().as_ref());
f(&arr[..])
})
} else if alg == Some(KeyAlg::Bls12_381(BlsCurves::G2)) {
ArrayKey::<U96>::temp(|arr| {
arr.copy_from_slice(buf.1.to_bytes().as_ref());
f(&arr[..])
})
} else {
ArrayKey::<U144>::temp(|arr| {
arr[0..48].copy_from_slice(buf.0.to_bytes().as_ref());
arr[48..].copy_from_slice(buf.1.to_bytes().as_ref());
f(&arr[..])
})
}
}
}
impl From<&BlsKeyPair<G1G2>> for BlsKeyPair<G1> {
fn from(kp: &BlsKeyPair<G1G2>) -> Self {
BlsKeyPair {
secret: kp.secret.clone(),
public: kp.public.0,
}
}
}
impl From<&BlsKeyPair<G1G2>> for BlsKeyPair<G2> {
fn from(kp: &BlsKeyPair<G1G2>) -> Self {
BlsKeyPair {
secret: kp.secret.clone(),
public: kp.public.1,
}
}
}
#[derive(Clone, Debug, PartialEq, Eq, Zeroize)]
/// A utility struct combining G1 and G2 public keys
pub struct G1G2Pair(G1Affine, G2Affine);
#[cfg(test)]
mod tests {
use base64::Engine;
use std::string::ToString;
use super::*;
use crate::repr::{ToPublicBytes, ToSecretBytes};
// test against EIP-2333 (as updated for signatures draft 4)
#[test]
fn key_gen_expected() {
let seed = &hex!(
"c55257c360c07c72029aebc1b53c05ed0362ada38ead3e3e9efa3708e5349553
1f09a6987599d18264c1e1c92f2cf141630c7a3c4ab7c81b2f001698e7463b04"
);
let kp = BlsKeyPair::<G1>::from_seed(&seed[..]).unwrap();
let sk = kp.to_secret_bytes().unwrap();
assert_eq!(
sk.as_hex().to_string(),
"0d7359d57963ab8fbbde1852dcf553fedbc31f464d80ee7d40ae683122b45070"
);
}
#[test]
fn g1_key_expected() {
let sk = hex!("0d7359d57963ab8fbbde1852dcf553fedbc31f464d80ee7d40ae683122b45070");
let kp = BlsKeyPair::<G1>::from_secret_bytes(&sk[..]).unwrap();
let pk = kp.to_public_bytes().unwrap();
assert_eq!(
pk.as_hex().to_string(),
"a2c975348667926acf12f3eecb005044e08a7a9b7d95f30bd281b55445107367a2e5d0558be7943c8bd13f9a1a7036fb"
);
assert_eq!(
BlsKeyPair::<G1>::from_public_bytes(pk.as_ref())
.unwrap()
.to_public_bytes()
.unwrap(),
pk
);
}
#[test]
fn g2_key_expected() {
let sk = hex!("0d7359d57963ab8fbbde1852dcf553fedbc31f464d80ee7d40ae683122b45070");
let kp = BlsKeyPair::<G2>::from_secret_bytes(&sk[..]).unwrap();
let pk = kp.to_public_bytes().unwrap();
assert_eq!(
pk.as_hex().to_string(),
"a5e43d5ecb7b8c01ceb3b91f7413b628ef02c6859dc42a4354b21f9195531988a648655037faafd1bac2fd2d7d9466180baa3705a45a6c597853db51eaf431616057fd8049c6bee8764292f9a104200a45a63ceae9d3c368643ab9e5ff0f8810"
);
assert_eq!(
BlsKeyPair::<G2>::from_public_bytes(pk.as_ref())
.unwrap()
.to_public_bytes()
.unwrap(),
pk
);
}
#[test]
fn g1g2_key_expected() {
let sk = hex!("0d7359d57963ab8fbbde1852dcf553fedbc31f464d80ee7d40ae683122b45070");
let kp = BlsKeyPair::<G1G2>::from_secret_bytes(&sk[..]).unwrap();
let pk = kp.to_public_bytes().unwrap();
assert_eq!(
pk.as_hex().to_string(),
"a2c975348667926acf12f3eecb005044e08a7a9b7d95f30bd281b55445107367a2e5d0558be7943c8bd13f9a1a7036fb\
a5e43d5ecb7b8c01ceb3b91f7413b628ef02c6859dc42a4354b21f9195531988a648655037faafd1bac2fd2d7d9466180baa3705a45a6c597853db51eaf431616057fd8049c6bee8764292f9a104200a45a63ceae9d3c368643ab9e5ff0f8810"
);
assert_eq!(
BlsKeyPair::<G1G2>::from_public_bytes(pk.as_ref())
.unwrap()
.to_public_bytes()
.unwrap(),
pk
);
}
#[test]
fn g1_jwk_expected() {
let test_pvt = &hex!("0d7359d57963ab8fbbde1852dcf553fedbc31f464d80ee7d40ae683122b45070");
let test_pub_g1 = &hex!("a2c975348667926acf12f3eecb005044e08a7a9b7d95f30bd281b55445107367a2e5d0558be7943c8bd13f9a1a7036fb");
let kp = BlsKeyPair::<G1>::from_secret_bytes(&test_pvt[..]).expect("Error creating key");
let jwk = kp.to_jwk_public(None).expect("Error converting key to JWK");
let jwk = JwkParts::try_from_str(&jwk).expect("Error parsing JWK");
assert_eq!(jwk.kty, JWK_KEY_TYPE);
assert_eq!(jwk.crv, G1::JWK_CURVE);
assert_eq!(
jwk.x,
base64::engine::general_purpose::URL_SAFE_NO_PAD
.encode(test_pub_g1)
.as_str()
);
assert_eq!(jwk.d, None);
let pk_load = BlsKeyPair::<G1>::from_jwk_parts(jwk).unwrap();
assert_eq!(kp.to_public_bytes(), pk_load.to_public_bytes());
let jwk = kp.to_jwk_secret(None).expect("Error converting key to JWK");
let jwk = JwkParts::from_slice(&jwk).expect("Error parsing JWK");
assert_eq!(jwk.kty, JWK_KEY_TYPE);
assert_eq!(jwk.crv, G1::JWK_CURVE);
assert_eq!(
jwk.x,
base64::engine::general_purpose::URL_SAFE_NO_PAD
.encode(test_pub_g1)
.as_str()
);
assert_eq!(
jwk.d,
base64::engine::general_purpose::URL_SAFE_NO_PAD
.encode(test_pvt)
.as_str()
);
let _sk_load = BlsKeyPair::<G1>::from_jwk_parts(jwk).unwrap();
// assert_eq!(
// kp.to_keypair_bytes().unwrap(),
// sk_load.to_keypair_bytes().unwrap()
// );
}
#[cfg(feature = "any_key")]
#[test]
// test loading of a key with the EC key type
fn g1_jwk_any_compat() {
use crate::alg::{any::AnyKey, BlsCurves, KeyAlg};
use alloc::boxed::Box;
let test_jwk_compat = r#"
{
"crv": "BLS12381_G1",
"kty": "EC",
"x": "osl1NIZnkmrPEvPuywBQROCKept9lfML0oG1VEUQc2ei5dBVi-eUPIvRP5oacDb7"
}"#;
let key = Box::<AnyKey>::from_jwk(test_jwk_compat).expect("Error decoding BLS key JWK");
assert_eq!(key.algorithm(), KeyAlg::Bls12_381(BlsCurves::G1));
let as_bls = key
.downcast_ref::<BlsKeyPair<G1>>()
.expect("Error downcasting BLS key");
let _ = as_bls
.to_jwk_public(None)
.expect("Error converting key to JWK");
}
}