cl: add nullifier module
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@ -12,3 +12,4 @@ group = "0.13.0"
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rand_core = "0.6.0"
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rand_chacha = "0.3.1"
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lazy_static = "1.4.0"
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hex = "0.4.3"
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@ -1,5 +1,6 @@
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mod crypto;
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mod note;
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mod nullifier;
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fn main() {
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println!("Hello, world!");
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@ -0,0 +1,107 @@
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// The Nullifier is used to detect if a note has
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// already been consumed.
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// The same nullifier secret may be used across multiple
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// notes to allow users to hold fewer secrets. A note
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// nonce is used to disambiguate when the same nullifier
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// secret is used for multiple notes.
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use blake2::{Blake2s256, Digest};
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use hex;
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use rand_core::{RngCore, SeedableRng};
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// Maintained privately by note holder
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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pub struct NullifierSecret([u8; 16]);
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// Nullifier commitment is public information that
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// can be provided to anyone wishing to transfer
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// you a note
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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pub struct NullifierCommitment([u8; 32]);
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// To allow users to maintain fewer nullifier secrets, we
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// provide a nonce to differentiate notes controlled by the same
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// secret. Each note is assigned a unique nullifier nonce.
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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pub struct NullifierNonce([u8; 16]);
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// The nullifier attached to input notes to prove an input has not
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// already been spent.
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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pub struct Nullifier([u8; 32]);
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impl NullifierSecret {
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fn random(mut rng: impl RngCore) -> Self {
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let mut sk = [0u8; 16];
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rng.fill_bytes(&mut sk);
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Self(sk)
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}
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fn commit(&self) -> NullifierCommitment {
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let mut hasher = Blake2s256::new();
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hasher.update(b"NOMOS_CL_NULL_COMMIT");
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hasher.update(&self.0);
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let commit_bytes: [u8; 32] = hasher.finalize().into();
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NullifierCommitment(commit_bytes)
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}
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}
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impl NullifierCommitment {
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pub fn to_hex(&self) -> String {
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hex::encode(&self.0)
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}
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}
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impl NullifierNonce {
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fn random(mut rng: impl RngCore) -> Self {
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let mut nonce = [0u8; 16];
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rng.fill_bytes(&mut nonce);
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Self(nonce)
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}
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}
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impl Nullifier {
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fn new(sk: NullifierSecret, nonce: NullifierNonce) -> Self {
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let mut hasher = Blake2s256::new();
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hasher.update(b"NOMOS_CL_NULLIFIER");
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hasher.update(&sk.0);
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hasher.update(&nonce.0);
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let nf_bytes: [u8; 32] = hasher.finalize().into();
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Self(nf_bytes)
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}
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}
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fn seed_rng(seed: u64) -> impl rand_core::RngCore {
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let mut bytes = [0u8; 32];
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(&mut bytes[..8]).copy_from_slice(&seed.to_le_bytes());
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rand_chacha::ChaCha12Rng::from_seed(bytes)
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}
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#[test]
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fn test_nullifier_commitment_vectors() {
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assert_eq!(
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NullifierSecret([0u8; 16]).commit().to_hex(),
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"384318f9864fe57647bac344e2afdc500a672dedb29d2dc63b004e940e4b382a"
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);
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assert_eq!(
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NullifierSecret([1u8; 16]).commit().to_hex(),
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"0fd667e6bb39fbdc35d6265726154b839638ea90bcf4e736953ccf27ca5f870b"
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);
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assert_eq!(
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NullifierSecret([u8::MAX; 16]).commit().to_hex(),
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"1cb78e487eb0b3116389311fdde84cd3f619a4d7f487b29bf5a002eed3784d75"
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);
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}
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#[test]
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fn test_nullifier_same_sk_different_nonce() {
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let sk = NullifierSecret::random(seed_rng(0));
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let nonce_1 = NullifierNonce::random(seed_rng(1));
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let nonce_2 = NullifierNonce::random(seed_rng(2));
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let nf_1 = Nullifier::new(sk, nonce_1);
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let nf_2 = Nullifier::new(sk, nonce_2);
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assert_ne!(nf_1, nf_2);
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}
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