[#792] zcash_primitives: implement Seed Signature section of ZIP-32
Implements a type to enclose a Seed Fingerprint byte sequence called `SeedFingerprint` implements a public function to create a `SeedFingerprint` from seed bytes Closes #792 Credits for PR Suggestions by Daira and Kris Edit: Added suggestions from Daira Emma and a test for returning `None` Added test refactor suggestions as well removed reference to test vectors
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@ -6,7 +6,7 @@ use memuse::{self, DynamicUsage};
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use subtle::{Choice, ConditionallySelectable};
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use crate::sapling::{Diversifier, NullifierDerivingKey, PaymentAddress, ViewingKey};
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pub mod fingerprint;
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pub mod sapling;
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#[deprecated(note = "Please use the types exported from the `zip32::sapling` module instead.")]
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@ -0,0 +1,80 @@
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//! Seed Fingerprints according to ZIP 32
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//!
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//! Implements section `Seed Fingerprints` of Shielded Hierarchical Deterministic Wallets (ZIP 32)
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//!
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//! [Section Seed Fingerprints]: https://zips.z.cash/zip-0032#seed-fingerprints
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use blake2b_simd::Params as Blake2bParams;
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pub const ZIP32_SEED_FP_PERSONALIZATION: &[u8; 16] = b"Zcash_HD_Seed_FP";
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pub struct SeedFingerprint([u8; 32]);
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impl SeedFingerprint {
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/// Return the seed fingerprint of the wallet as defined in
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/// <https://zips.z.cash/zip-0032#seed-fingerprints> or None
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/// if the length of `seed_bytes` is less than 32 or
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/// greater than 252.
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pub fn from_seed(seed_bytes: &[u8]) -> Option<SeedFingerprint> {
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let seed_len = seed_bytes.len();
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if (32..=252).contains(&seed_len) {
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let seed_len: u8 = seed_len.try_into().unwrap();
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Some(SeedFingerprint(
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Blake2bParams::new()
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.hash_length(32)
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.personal(ZIP32_SEED_FP_PERSONALIZATION)
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.to_state()
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.update(&[seed_len])
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.update(seed_bytes)
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.finalize()
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.as_bytes()
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.try_into()
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.expect("hash length should be 32 bytes"),
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))
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} else {
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None
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}
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}
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/// Returns the fingerprint as a byte array.
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pub fn to_bytes(&self) -> [u8; 32] {
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self.0
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}
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}
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#[test]
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fn test_seed_fingerprint() {
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struct TestVector {
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root_seed: Vec<u8>,
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fingerprint: Vec<u8>,
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}
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let test_vectors = vec![TestVector {
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root_seed: vec![
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0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d,
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0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b,
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0x1c, 0x1d, 0x1e, 0x1f,
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],
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fingerprint: vec![
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0xde, 0xff, 0x60, 0x4c, 0x24, 0x67, 0x10, 0xf7, 0x17, 0x6d, 0xea, 0xd0, 0x2a, 0xa7,
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0x46, 0xf2, 0xfd, 0x8d, 0x53, 0x89, 0xf7, 0x7, 0x25, 0x56, 0xdc, 0xb5, 0x55, 0xfd,
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0xbe, 0x5e, 0x3a, 0xe3,
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],
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}];
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for tv in test_vectors {
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let fp = SeedFingerprint::from_seed(&tv.root_seed).expect("root_seed has valid length");
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assert_eq!(&fp.to_bytes(), &tv.fingerprint[..]);
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}
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}
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#[test]
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fn test_seed_fingerprint_is_none() {
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let odd_seed = vec![
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0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e,
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0x0f,
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];
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assert!(
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SeedFingerprint::from_seed(&odd_seed).is_none(),
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"fingerprint from short seed should be `None`"
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);
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}
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