1# Miden Crypto
 2This crate contains cryptographic primitives used in Polygon Miden.
 3
 4## Hash
 5[Hash module](./src/hash) provides a set of cryptographic hash functions which are used by the Miden VM and the Miden rollup. Currently, these functions are:
 6
 7* [BLAKE3](https://github.com/BLAKE3-team/BLAKE3) hash function with 256-bit, 192-bit, or 160-bit output. The 192-bit and 160-bit outputs are obtained by truncating the 256-bit output of the standard BLAKE3.
 8* [RPO](https://eprint.iacr.org/2022/1577) hash function with 256-bit output. This hash function is an algebraic hash function suitable for recursive STARKs.
 9
10For performance benchmarks of these hash functions and their comparison to other popular hash functions please see [here](./benches/).
11
12## Merkle
13[Merkle module](./src/merkle/) provides a set of data structures related to Merkle trees. All these data structures are implemented using the RPO hash function described above. The data structures are:
14
15* `MerkleTree`: a regular fully-balanced binary Merkle tree. The depth of this tree can be at most 64.
16* `MerklePathSet`: a collection of Merkle authentication paths all resolving to the same root. The length of the paths can be at most 64.
17* `MerkleStore`: a collection of Merkle trees of different heights designed to efficiently store trees with common subtrees.
18* `Mmr`: a Merkle mountain range structure designed to function as an append-only log.
19* `SimpleSmt`: a Sparse Merkle Tree (with no compaction), mapping 64-bit keys to 4-element values.
20* `TieredSmt`: a Sparse Merkle tree (with compaction), mapping 4-element keys to 4-element values.
21
22The module also contains additional supporting components such as `NodeIndex`, `MerklePath`,  and `MerkleError`  to assist with tree indexation, opening proofs, and reporting inconsistent arguments/state.
23
24## Crate features
25This crate can be compiled with the following features:
26
27* `std` - enabled by default and relies on the Rust standard library.
28* `no_std` does not rely on the Rust standard library and enables compilation to WebAssembly.
29
30Both of these features imply the use of [alloc](https://doc.rust-lang.org/alloc/) to support heap-allocated collections.
31
32To compile with `no_std`, disable default features via `--no-default-features` flag.
33
34## Testing
35
36You can use cargo defaults to test the library:
37
38```shell
39cargo test
40```
41
42However, some of the functions are heavy and might take a while for the tests to complete. In order to test in release mode, we have to replicate the test conditions of the development mode so all debug assertions can be verified.
43
44We do that by enabling some special [flags](https://doc.rust-lang.org/cargo/reference/profiles.html) for the compilation.
45
46```shell
47RUSTFLAGS="-C debug-assertions -C overflow-checks -C debuginfo=2" cargo test --release
48```
49
50## License
51This project is [MIT licensed](./LICENSE).