libro 0.90.0

Cryptographic audit chain — tamper-proof event logging with hash-linked entries and verification
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60

//! Internal hash abstraction.
//!
//! Defaults to BLAKE3 (4-10x faster than SHA-256, 256-bit output, 128-bit collision resistance).
//! Enable the `sha256` feature for NIST FIPS 180-4 compliance environments.

/// The hash algorithm identifier embedded in chain entries.
///
/// This enables verification across algorithm transitions — a verifier
/// can select the correct algorithm based on the stored identifier.
#[cfg(not(feature = "sha256"))]
pub(crate) const HASH_ALGORITHM: &str = "blake3";
#[cfg(feature = "sha256")]
pub(crate) const HASH_ALGORITHM: &str = "sha256";

/// A streaming hasher that accumulates data and produces a hex-encoded digest.
pub(crate) struct ChainHasher {
    #[cfg(not(feature = "sha256"))]
    inner: blake3::Hasher,
    #[cfg(feature = "sha256")]
    inner: sha2::Sha256,
}

impl ChainHasher {
    /// Create a new hasher.
    #[inline]
    pub fn new() -> Self {
        Self {
            #[cfg(not(feature = "sha256"))]
            inner: blake3::Hasher::new(),
            #[cfg(feature = "sha256")]
            inner: <sha2::Sha256 as sha2::Digest>::new(),
        }
    }

    /// Feed data into the hasher.
    #[inline]
    pub fn update(&mut self, data: &[u8]) {
        #[cfg(not(feature = "sha256"))]
        {
            self.inner.update(data);
        }
        #[cfg(feature = "sha256")]
        {
            <sha2::Sha256 as sha2::Digest>::update(&mut self.inner, data);
        }
    }

    /// Finalize and return the hex-encoded digest.
    #[inline]
    pub fn finalize_hex(self) -> String {
        #[cfg(not(feature = "sha256"))]
        {
            self.inner.finalize().to_hex().to_string()
        }
        #[cfg(feature = "sha256")]
        {
            format!("{:x}", <sha2::Sha256 as sha2::Digest>::finalize(self.inner))
        }
    }
}