initial commit

Signed-off-by: Kamal Tufekcic <kamal@lo.sh>

soliton/src/primitives/sha3_256.rs

@@ -0,0 +1,82 @@
+//! SHA3-256 hashing (FIPS 202).
+
+use sha3::{Digest, Sha3_256};
+
+/// Compute SHA3-256 hash of `data`.
+#[must_use]
+pub fn hash(data: &[u8]) -> [u8; 32] {
+    Sha3_256::digest(data).into()
+}
+
+/// Compute the hex-encoded fingerprint (SHA3-256) of a public key.
+#[must_use]
+pub fn fingerprint_hex(pk: &[u8]) -> String {
+    let digest = hash(pk);
+    hex_encode(&digest)
+}
+
+/// Encode bytes as lowercase hex string.
+fn hex_encode(bytes: &[u8]) -> String {
+    use std::fmt::Write;
+    let mut s = String::with_capacity(bytes.len() * 2);
+    for &b in bytes {
+        // fmt::Write for String is infallible — the Result is always Ok.
+        let _ = write!(s, "{b:02x}");
+    }
+    s
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use hex_literal::hex;
+
+    #[test]
+    fn empty_input() {
+        assert_eq!(
+            hash(b""),
+            hex!("a7ffc6f8bf1ed76651c14756a061d662f580ff4de43b49fa82d80a4b80f8434a")
+        );
+    }
+
+    #[test]
+    fn abc() {
+        assert_eq!(
+            hash(b"abc"),
+            hex!("3a985da74fe225b2045c172d6bd390bd855f086e3e9d525b46bfe24511431532")
+        );
+    }
+
+    #[test]
+    fn long_message() {
+        assert_eq!(
+            hash(b"abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"),
+            hex!("41c0dba2a9d6240849100376a8235e2c82e1b9998a999e21db32dd97496d3376")
+        );
+    }
+
+    #[test]
+    fn fingerprint_hex_format() {
+        let fp = fingerprint_hex(b"test");
+        assert_eq!(fp.len(), 64);
+        assert!(
+            fp.chars()
+                .all(|c| c.is_ascii_hexdigit() && !c.is_ascii_uppercase())
+        );
+    }
+
+    #[test]
+    fn fingerprint_hex_deterministic() {
+        let a = fingerprint_hex(b"test");
+        let b = fingerprint_hex(b"test");
+        assert_eq!(a, b);
+    }
+
+    #[test]
+    fn fingerprint_hex_matches_hash() {
+        let data = b"hello world";
+        let fp = fingerprint_hex(data);
+        let expected = hex::encode(hash(data));
+        assert_eq!(fp, expected);
+    }
+}