Initial ChronoSeal release

shared/src/hashing.rs

@@ -0,0 +1,42 @@
+use blake3::Hasher;
+use crate::protocol::{EntropyData, StackState};
+
+/// Initial hash for a brand-new session: Blake3(session_id || pub_key || salt)
+pub fn initial_hash(session_id: &str, pub_key: &[u8], salt: &[u8]) -> Vec<u8> {
+    let mut h = Hasher::new();
+    h.update(session_id.as_bytes());
+    h.update(pub_key);
+    h.update(salt);
+    h.finalize().as_bytes().to_vec()
+}
+
+/// Next hash in the chain: Blake3 with the salt mixed in (no keyed mode needed)
+pub fn next_chain_hash(
+    prev_hash: &[u8],
+    timestamp: u64,
+    entropy: &EntropyData,
+    stack: &StackState,
+    salt: &[u8],
+) -> Vec<u8> {
+    let entropy_json = serde_json::to_string(entropy).unwrap();
+    let stack_json = serde_json::to_string(stack).unwrap();
+
+    let entropy_hash = blake3::hash(entropy_json.as_bytes());
+    let stack_hash = blake3::hash(stack_json.as_bytes());
+
+    let mut h = Hasher::new();
+    // Mix the salt into the hash state
+    h.update(salt);
+    h.update(prev_hash);
+    h.update(&timestamp.to_le_bytes());
+    h.update(entropy_hash.as_bytes());
+    h.update(stack_hash.as_bytes());
+    h.finalize().as_bytes().to_vec()
+}
+
+/// Hash of all stack items for VM HASH opcode
+pub fn hash_stack(stack: &[u32]) -> u32 {
+    let data: Vec<u8> = stack.iter().flat_map(|x| x.to_le_bytes()).collect();
+    let hash = blake3::hash(&data);
+    u32::from_le_bytes(hash.as_bytes()[..4].try_into().unwrap())
+}