2025-08-22 18:11:45 -03:00

340 lines
11 KiB
Rust

use chacha20::{
ChaCha20,
cipher::{KeyIvInit, StreamCipher},
};
use risc0_zkvm::{
serde::to_vec,
sha::{Impl, Sha256},
};
use serde::{Deserialize, Serialize};
#[cfg(feature = "host")]
use crate::error::NssaCoreError;
use crate::{
account::{
Account, AccountWithMetadata, Commitment, Nonce, Nullifier, NullifierPublicKey,
NullifierSecretKey,
},
program::{ProgramId, ProgramOutput},
};
#[cfg(feature = "host")]
use std::io::{Cursor, Read};
pub mod account;
pub mod program;
use k256::{
AffinePoint, EncodedPoint, FieldBytes, ProjectivePoint, PublicKey, Scalar,
elliptic_curve::{
PrimeField,
sec1::{FromEncodedPoint, ToEncodedPoint},
},
};
#[cfg(feature = "host")]
pub mod error;
pub type CommitmentSetDigest = [u8; 32];
pub type MembershipProof = (usize, Vec<[u8; 32]>);
pub fn verify_membership_proof(
commitment: &Commitment,
proof: &MembershipProof,
digest: &CommitmentSetDigest,
) -> bool {
let value_bytes = commitment.to_byte_array();
let mut result: [u8; 32] = Impl::hash_bytes(&value_bytes)
.as_bytes()
.try_into()
.unwrap();
let mut level_index = proof.0;
for node in &proof.1 {
let is_left_child = level_index & 1 == 0;
if is_left_child {
let mut bytes = [0u8; 64];
bytes[..32].copy_from_slice(&result);
bytes[32..].copy_from_slice(node);
result = Impl::hash_bytes(&bytes).as_bytes().try_into().unwrap();
} else {
let mut bytes = [0u8; 64];
bytes[..32].copy_from_slice(node);
bytes[32..].copy_from_slice(&result);
result = Impl::hash_bytes(&bytes).as_bytes().try_into().unwrap();
}
level_index >>= 1;
}
&result == digest
}
pub type EphemeralPublicKey = Secp256k1Point;
pub type IncomingViewingPublicKey = Secp256k1Point;
pub type EphemeralSecretKey = [u8; 32];
impl From<&EphemeralSecretKey> for EphemeralPublicKey {
fn from(value: &EphemeralSecretKey) -> Self {
Secp256k1Point::from_scalar(*value)
}
}
#[derive(Serialize, Deserialize, Clone)]
#[cfg_attr(any(feature = "host", test), derive(Debug, PartialEq, Eq))]
pub struct Secp256k1Point(pub Vec<u8>);
impl Secp256k1Point {
pub fn from_scalar(value: [u8; 32]) -> Secp256k1Point {
let x_bytes: FieldBytes = value.into();
let x = Scalar::from_repr(x_bytes).unwrap();
let p = ProjectivePoint::GENERATOR * x;
let q = AffinePoint::from(p);
let enc = q.to_encoded_point(true);
Self(enc.as_bytes().to_vec())
}
}
#[derive(Serialize, Deserialize)]
#[cfg_attr(any(feature = "host", test), derive(Debug, Clone, PartialEq, Eq))]
pub struct EncryptedAccountData {
ciphertext: Vec<u8>,
epk: EphemeralPublicKey,
view_tag: u8,
}
impl EncryptedAccountData {
#[cfg(feature = "host")]
pub fn decrypt(self, isk: &[u8; 32], output_index: u32) -> Option<Account> {
let ss_bytes = Self::ecdh(isk, &self.epk.0.clone().try_into().unwrap());
let ipk = IncomingViewingPublicKey::from_scalar(*isk);
let key = Self::kdf(
ss_bytes,
&self.epk,
&ipk,
// &commitment.to_byte_array(),
output_index,
);
let mut cipher = ChaCha20::new(&key.into(), &[0; 12].into());
let mut buffer = self.ciphertext;
cipher.apply_keystream(&mut buffer);
let mut cursor = Cursor::new(buffer.as_slice());
Account::from_cursor(&mut cursor).ok()
}
pub fn new(
account: &Account,
// commitment: &Commitment,
esk: &EphemeralSecretKey,
npk: &NullifierPublicKey,
ipk: &IncomingViewingPublicKey,
output_index: u32,
) -> Self {
let mut buffer = account.to_bytes().to_vec();
let ss_bytes = Self::ecdh(esk, &ipk.0.clone().try_into().unwrap());
let epk = EphemeralPublicKey::from(esk);
let key = Self::kdf(
ss_bytes,
&epk,
ipk,
// &commitment.to_byte_array(),
output_index,
);
let mut cipher = ChaCha20::new(&key.into(), &[0; 12].into());
cipher.apply_keystream(&mut buffer);
let view_tag = Self::view_tag(&npk, &ipk);
Self {
ciphertext: buffer,
epk,
view_tag,
}
}
pub fn kdf(
ss_bytes: [u8; 32],
epk: &EphemeralPublicKey,
ipk: &IncomingViewingPublicKey,
// commitment: &[u8; 32],
output_index: u32,
) -> [u8; 32] {
let mut bytes = Vec::new();
bytes.extend_from_slice(b"NSSA/v0.1/KDF-SHA256");
bytes.extend_from_slice(&ss_bytes);
bytes.extend_from_slice(&epk.0[..]);
bytes.extend_from_slice(&ipk.0[..]);
// bytes.extend_from_slice(&commitment[..]);
bytes.extend_from_slice(&output_index.to_le_bytes());
Impl::hash_bytes(&bytes).as_bytes().try_into().unwrap()
}
pub fn ecdh(scalar: &[u8; 32], point: &[u8; 33]) -> [u8; 32] {
let scalar = Scalar::from_repr((*scalar).into()).unwrap();
let encoded = EncodedPoint::from_bytes(point).unwrap();
let pubkey_affine = AffinePoint::from_encoded_point(&encoded).unwrap();
let shared = ProjectivePoint::from(pubkey_affine) * scalar;
let shared_affine = shared.to_affine();
let encoded = shared_affine.to_encoded_point(false);
let x_bytes_slice = encoded.x().unwrap();
let mut x_bytes = [0u8; 32];
x_bytes.copy_from_slice(x_bytes_slice);
x_bytes
}
#[cfg(feature = "host")]
pub fn from_cursor(cursor: &mut Cursor<&[u8]>) -> Result<Self, NssaCoreError> {
let mut u32_bytes = [0; 4];
cursor.read_exact(&mut u32_bytes)?;
let ciphertext_lenght = u32::from_le_bytes(u32_bytes);
let mut ciphertext = vec![0; ciphertext_lenght as usize];
cursor.read_exact(&mut ciphertext)?;
let mut epk_bytes = vec![0; 33];
cursor.read_exact(&mut epk_bytes)?;
let mut tag_bytes = [0; 1];
cursor.read_exact(&mut tag_bytes)?;
Ok(Self {
ciphertext,
epk: Secp256k1Point(epk_bytes),
view_tag: tag_bytes[0],
})
}
fn view_tag(npk: &NullifierPublicKey, ipk: &&IncomingViewingPublicKey) -> u8 {
// TODO: implement
0
}
}
impl EncryptedAccountData {
pub fn to_bytes(&self) -> Vec<u8> {
let mut bytes = Vec::new();
let ciphertext_length: u32 = self.ciphertext.len() as u32;
bytes.extend_from_slice(&ciphertext_length.to_le_bytes());
bytes.extend_from_slice(&self.ciphertext);
bytes.extend_from_slice(&self.epk.0);
bytes.push(self.view_tag);
bytes
}
}
#[derive(Serialize, Deserialize)]
pub struct PrivacyPreservingCircuitInput {
pub program_output: ProgramOutput,
pub visibility_mask: Vec<u8>,
pub private_account_nonces: Vec<Nonce>,
pub private_account_keys: Vec<(
NullifierPublicKey,
IncomingViewingPublicKey,
EphemeralSecretKey,
)>,
pub private_account_auth: Vec<(NullifierSecretKey, MembershipProof)>,
pub program_id: ProgramId,
pub commitment_set_digest: CommitmentSetDigest,
}
#[derive(Serialize, Deserialize)]
#[cfg_attr(any(feature = "host", test), derive(Debug, PartialEq, Eq))]
pub struct PrivacyPreservingCircuitOutput {
pub public_pre_states: Vec<AccountWithMetadata>,
pub public_post_states: Vec<Account>,
pub encrypted_private_post_states: Vec<EncryptedAccountData>,
pub new_commitments: Vec<Commitment>,
pub new_nullifiers: Vec<Nullifier>,
pub commitment_set_digest: CommitmentSetDigest,
}
#[cfg(feature = "host")]
impl PrivacyPreservingCircuitOutput {
pub fn to_bytes(&self) -> Vec<u8> {
bytemuck::cast_slice(&to_vec(&self).unwrap()).to_vec()
}
}
#[cfg(test)]
mod tests {
use std::io::Cursor;
use risc0_zkvm::serde::from_slice;
use crate::{
EncryptedAccountData, EphemeralPublicKey, PrivacyPreservingCircuitOutput, Secp256k1Point,
account::{Account, AccountWithMetadata, Commitment, Nullifier, NullifierPublicKey},
};
#[test]
fn test_privacy_preserving_circuit_output_to_bytes_is_compatible_with_from_slice() {
let output = PrivacyPreservingCircuitOutput {
public_pre_states: vec![
AccountWithMetadata {
account: Account {
program_owner: [1, 2, 3, 4, 5, 6, 7, 8],
balance: 12345678901234567890,
data: b"test data".to_vec(),
nonce: 18446744073709551614,
},
is_authorized: true,
},
AccountWithMetadata {
account: Account {
program_owner: [9, 9, 9, 8, 8, 8, 7, 7],
balance: 123123123456456567112,
data: b"test data".to_vec(),
nonce: 9999999999999999999999,
},
is_authorized: false,
},
],
public_post_states: vec![Account {
program_owner: [1, 2, 3, 4, 5, 6, 7, 8],
balance: 100,
data: b"post state data".to_vec(),
nonce: 18446744073709551615,
}],
encrypted_private_post_states: vec![EncryptedAccountData {
ciphertext: vec![255, 255, 1, 1, 2, 2],
epk: EphemeralPublicKey::from_scalar([123; 32]),
view_tag: 1,
}],
new_commitments: vec![Commitment::new(
&NullifierPublicKey::from(&[1; 32]),
&Account::default(),
)],
new_nullifiers: vec![Nullifier::new(
&Commitment::new(&NullifierPublicKey::from(&[2; 32]), &Account::default()),
&[1; 32],
)],
commitment_set_digest: [0xab; 32],
};
let bytes = output.to_bytes();
let output_from_slice: PrivacyPreservingCircuitOutput = from_slice(&bytes).unwrap();
assert_eq!(output, output_from_slice);
}
#[test]
fn test_encrypted_account_data_to_bytes_roundtrip() {
let data = EncryptedAccountData {
ciphertext: vec![255, 255, 1, 1, 2, 2],
epk: EphemeralPublicKey::from_scalar([123; 32]),
view_tag: 95,
};
let bytes = data.to_bytes();
let mut cursor = Cursor::new(bytes.as_slice());
let data_from_cursor = EncryptedAccountData::from_cursor(&mut cursor).unwrap();
assert_eq!(data, data_from_cursor);
}
}