106 lines
3.0 KiB
Rust
106 lines
3.0 KiB
Rust
use tiny_keccak::Keccak;
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pub fn hash(input: &[u8]) -> Vec<u8> {
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let mut keccak = Keccak::new_keccak256();
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keccak.update(input);
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let mut result = vec![0; 32];
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keccak.finalize(result.as_mut_slice());
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result
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}
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/// Get merkle root of some hashed values - the input leaf nodes is expected to already be hashed
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/// Outputs a `Vec<u8>` byte array of the merkle root given a set of leaf node values.
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pub fn merkle_root(values: &[Vec<u8>]) -> Option<Vec<u8>> {
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let values_len = values.len();
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// check size of vector > 0 and ^ 2
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if values.is_empty() || !values_len.is_power_of_two() {
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return None;
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}
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// vector to store hashes
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// filled with 0 as placeholders
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let mut o: Vec<Vec<u8>> = vec![vec![0]; values_len];
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// append values to the end
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o.append(&mut values.to_vec());
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// traverse backwards as values are at the end
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// then fill placeholders with a hash of two leaf nodes
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for i in (0..values_len).rev() {
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let mut current_value: Vec<u8> = o[i * 2].clone();
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current_value.append(&mut o[i * 2 + 1].clone());
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o[i] = hash(¤t_value[..]);
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}
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// the root hash will be at index 1
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return Some(o[1].clone());
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use std::convert::From;
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#[test]
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fn test_hashing() {
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let input: Vec<u8> = From::from("hello");
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let output = hash(input.as_ref());
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let expected = &[
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0x1c, 0x8a, 0xff, 0x95, 0x06, 0x85, 0xc2, 0xed, 0x4b, 0xc3, 0x17, 0x4f, 0x34, 0x72,
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0x28, 0x7b, 0x56, 0xd9, 0x51, 0x7b, 0x9c, 0x94, 0x81, 0x27, 0x31, 0x9a, 0x09, 0xa7,
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0xa3, 0x6d, 0xea, 0xc8,
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];
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assert_eq!(expected, output.as_slice());
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}
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#[test]
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fn test_merkle_root() {
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// hash the leaf nodes
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let mut input = vec![
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hash("a".as_bytes()),
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hash("b".as_bytes()),
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hash("c".as_bytes()),
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hash("d".as_bytes()),
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];
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// generate a merkle tree and return the root
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let output = merkle_root(&input[..]);
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// create merkle root manually
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let mut leaf_1_2: Vec<u8> = input[0].clone(); // a
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leaf_1_2.append(&mut input[1].clone()); // b
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let mut leaf_3_4: Vec<u8> = input[2].clone(); // c
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leaf_3_4.append(&mut input[3].clone()); // d
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let node_1 = hash(&leaf_1_2[..]);
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let node_2 = hash(&leaf_3_4[..]);
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let mut root: Vec<u8> = node_1.clone(); // ab
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root.append(&mut node_2.clone()); // cd
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let expected = hash(&root[..]);
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assert_eq!(&expected[..], output.unwrap().as_slice());
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}
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#[test]
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fn test_empty_input_merkle_root() {
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let input = vec![];
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let output = merkle_root(&input[..]);
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assert_eq!(None, output);
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}
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#[test]
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fn test_odd_leaf_merkle_root() {
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let input = vec![
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hash("a".as_bytes()),
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hash("b".as_bytes()),
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hash("a".as_bytes()),
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];
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let output = merkle_root(&input[..]);
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assert_eq!(None, output);
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}
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}
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