zip32/src/fingerprint.rs

108 lines
3.4 KiB
Rust

//! Seed Fingerprints according to ZIP 32
//!
//! Implements section [Seed Fingerprints] of Shielded Hierarchical Deterministic Wallets (ZIP 32).
//!
//! [Seed Fingerprints]: https://zips.z.cash/zip-0032#seed-fingerprints
use blake2b_simd::Params as Blake2bParams;
const ZIP32_SEED_FP_PERSONALIZATION: &[u8; 16] = b"Zcash_HD_Seed_FP";
/// The fingerprint for a wallet's seed bytes, as defined in [ZIP 32].
///
/// [ZIP 32]: https://zips.z.cash/zip-0032#seed-fingerprints
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct SeedFingerprint([u8; 32]);
impl ::core::fmt::Debug for SeedFingerprint {
fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
write!(f, "SeedFingerprint(")?;
for i in self.0 {
write!(f, "{:02x}", i)?;
}
write!(f, ")")?;
Ok(())
}
}
impl SeedFingerprint {
/// Derives the fingerprint of the given seed bytes.
///
/// Returns `None` if the length of `seed_bytes` is less than 32 or greater than 252.
pub fn from_seed(seed_bytes: &[u8]) -> Option<SeedFingerprint> {
let seed_len = seed_bytes.len();
if (32..=252).contains(&seed_len) {
let seed_len: u8 = seed_len.try_into().unwrap();
Some(SeedFingerprint(
Blake2bParams::new()
.hash_length(32)
.personal(ZIP32_SEED_FP_PERSONALIZATION)
.to_state()
.update(&[seed_len])
.update(seed_bytes)
.finalize()
.as_bytes()
.try_into()
.expect("hash length should be 32 bytes"),
))
} else {
None
}
}
/// Reconstructs the fingerprint from a buffer containing a previously computed fingerprint.
pub fn from_bytes(hash: [u8; 32]) -> Self {
Self(hash)
}
/// Returns the fingerprint as a byte array.
pub fn to_bytes(&self) -> [u8; 32] {
self.0
}
}
#[test]
fn test_seed_fingerprint() {
struct TestVector {
root_seed: [u8; 32],
fingerprint: [u8; 32],
fingerprint_str: &'static str,
}
let test_vectors = [TestVector {
root_seed: [
0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d,
0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b,
0x1c, 0x1d, 0x1e, 0x1f,
],
fingerprint: [
0xde, 0xff, 0x60, 0x4c, 0x24, 0x67, 0x10, 0xf7, 0x17, 0x6d, 0xea, 0xd0, 0x2a, 0xa7,
0x46, 0xf2, 0xfd, 0x8d, 0x53, 0x89, 0xf7, 0x7, 0x25, 0x56, 0xdc, 0xb5, 0x55, 0xfd,
0xbe, 0x5e, 0x3a, 0xe3,
],
fingerprint_str: "deff604c246710f7176dead02aa746f2fd8d5389f7072556dcb555fdbe5e3ae3",
}];
for tv in test_vectors {
let fp = SeedFingerprint::from_seed(&tv.root_seed).expect("root_seed has valid length");
assert_eq!(&fp.to_bytes(), &tv.fingerprint[..]);
assert_eq!(
std::format!("{:?}", fp),
std::format!("SeedFingerprint({})", tv.fingerprint_str)
);
}
}
#[test]
fn test_seed_fingerprint_is_none() {
let odd_seed = [
0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e,
0x0f,
];
assert!(
SeedFingerprint::from_seed(&odd_seed).is_none(),
"fingerprint from short seed should be `None`"
);
}