Merge pull request #16 from 0xPolygonMiden/next

Tracking PR for v0.1 release

.github/workflows/ci.yml

@@ -7,14 +7,39 @@ on:
     types: [opened, repoened, synchronize]
 
 jobs:
-  test:
-    name: Test Rust ${{matrix.toolchain}} on ${{matrix.os}}
+  build:
+    name: Build ${{matrix.toolchain}} on ${{matrix.os}} with ${{matrix.args}}
     runs-on: ${{matrix.os}}-latest
     strategy:
       fail-fast: false
       matrix:
         toolchain: [stable, nightly]
         os: [ubuntu]
+        target: [wasm32-unknown-unknown]
+        args: [--no-default-features --target wasm32-unknown-unknown]
+    steps:
+      - uses: actions/checkout@main
+      - name: Install rust
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: ${{matrix.toolchain}}
+          override: true
+      - run: rustup target add ${{matrix.target}}
+      - name: Test
+        uses: actions-rs/cargo@v1
+        with:
+          command: build
+          args: ${{matrix.args}}
+
+  test:
+    name: Test ${{matrix.toolchain}} on ${{matrix.os}} with ${{matrix.features}}
+    runs-on: ${{matrix.os}}-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        toolchain: [stable, nightly]
+        os: [ubuntu]
+        features: [--all-features, --no-default-features]
     steps:
       - uses: actions/checkout@main
       - name: Install rust
@@ -26,25 +51,29 @@ jobs:
         uses: actions-rs/cargo@v1
         with:
           command: test
+          args: ${{matrix.features}}
 
   clippy:
-    name: Clippy
+    name: Clippy with ${{matrix.features}}
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        features: [--all-features, --no-default-features]
     steps:
       - uses: actions/checkout@main
-      - name: Install minimal stable with clippy
+      - name: Install minimal nightly with clippy
         uses: actions-rs/toolchain@v1
         with:
           profile: minimal
-          toolchain: stable
+          toolchain: nightly
           components: clippy
           override: true
-
       - name: Clippy
         uses: actions-rs/cargo@v1
         with:
           command: clippy
-          args: --all -- -D clippy::all -D warnings
+          args: --all ${{matrix.features}} -- -D clippy::all -D warnings
 
   rustfmt:
     name: rustfmt

Cargo.toml

@@ -10,11 +10,21 @@ categories = ["cryptography", "no-std"]
 keywords = ["miden", "crypto", "hash", "merkle"]
 edition = "2021"
 
+[[bench]]
+name = "hash"
+harness = false
+
+[features]
+default = ["blake3/default", "std", "winter_crypto/default", "winter_math/default", "winter_utils/default"]
+std = ["blake3/std", "winter_crypto/std", "winter_math/std", "winter_utils/std"]
+
 [dependencies]
-winter_crypto = { version = "0.4.1", package = "winter-crypto" }
-winter_math = { version = "0.4.1", package = "winter-math" }
-winter_utils = { version = "0.4.1", package = "winter-utils" }
+blake3 = { version = "1.0", default-features = false }
+winter_crypto = { version = "0.4.1", package = "winter-crypto", default-features = false }
+winter_math = { version = "0.4.1", package = "winter-math", default-features = false }
+winter_utils = { version = "0.4.1", package = "winter-utils", default-features = false }
 
 [dev-dependencies]
+criterion = "0.4"
 proptest = "1.0.0"
 rand_utils = { version = "0.4", package = "winter-rand-utils" }

README.md

@@ -1,2 +1,27 @@
-# crypto
-Cryptographic primitives used in Polygon Miden rollup
+# Miden Crypto
+This crate contains cryptographic primitives used in Polygon Miden.
+
+## Hash
+[Hash module](./src/hash) provides a set of cryptographic hash functions which are used by Miden VM and Miden Rollup. Currently, these functions are:
+
+* [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.
+* [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.
+
+## Merkle
+[Merkle module](./src/merkle/) provides a set of data structures related to Merkle tree. All these data structures are implemented using RPO hash function described above. The data structure are:
+
+* `MerkleTree`: a regular fully-balanced binary Merkle tree. The depth of this tree can be at most 64.
+* `MerklePathSet`: a collection of Merkle authentication paths all resolving to the same root. The length of the paths can be at most 64.
+
+## Crate features
+This carate can be compiled with the following features:
+
+* `std` - enabled by default and relies on the Rust standard library.
+* `no_std` does not rely on the Rust standard library and enables compilation to WebAssembly.
+
+Both of these features imply use of [alloc](https://doc.rust-lang.org/alloc/) to support heap-allocated collections.
+
+To compile with `no_std`, disable default features via `--no-default-features` flag.
+
+## License
+This project is [MIT licensed](./LICENSE).

benches/hash.rs

@@ -0,0 +1,57 @@
+use criterion::{black_box, criterion_group, criterion_main, BatchSize, Criterion};
+use miden_crypto::{
+    hash::rpo::{Rpo256, RpoDigest},
+    Felt,
+};
+use rand_utils::rand_value;
+
+fn rpo256_2to1(c: &mut Criterion) {
+    let v: [RpoDigest; 2] = [Rpo256::hash(&[1_u8]), Rpo256::hash(&[2_u8])];
+    c.bench_function("RPO256 2-to-1 hashing (cached)", |bench| {
+        bench.iter(|| Rpo256::merge(black_box(&v)))
+    });
+
+    c.bench_function("RPO256 2-to-1 hashing (random)", |bench| {
+        bench.iter_batched(
+            || {
+                [
+                    Rpo256::hash(&rand_value::<u64>().to_le_bytes()),
+                    Rpo256::hash(&rand_value::<u64>().to_le_bytes()),
+                ]
+            },
+            |state| Rpo256::merge(&state),
+            BatchSize::SmallInput,
+        )
+    });
+}
+
+fn rpo256_sequential(c: &mut Criterion) {
+    let v: [Felt; 100] = (0..100)
+        .into_iter()
+        .map(Felt::new)
+        .collect::<Vec<Felt>>()
+        .try_into()
+        .expect("should not fail");
+    c.bench_function("RPO256 sequential hashing (cached)", |bench| {
+        bench.iter(|| Rpo256::hash_elements(black_box(&v)))
+    });
+
+    c.bench_function("RPO256 sequential hashing (random)", |bench| {
+        bench.iter_batched(
+            || {
+                let v: [Felt; 100] = (0..100)
+                    .into_iter()
+                    .map(|_| Felt::new(rand_value()))
+                    .collect::<Vec<Felt>>()
+                    .try_into()
+                    .expect("should not fail");
+                v
+            },
+            |state| Rpo256::hash_elements(&state),
+            BatchSize::SmallInput,
+        )
+    });
+}
+
+criterion_group!(hash_group, rpo256_sequential, rpo256_2to1);
+criterion_main!(hash_group);

src/hash/blake/mod.rs

@@ -0,0 +1,319 @@
+use super::{Digest, ElementHasher, Felt, FieldElement, Hasher, StarkField};
+use crate::utils::{ByteReader, ByteWriter, Deserializable, DeserializationError, Serializable};
+use core::{
+    mem::{size_of, transmute, transmute_copy},
+    ops::Deref,
+    slice::from_raw_parts,
+};
+
+#[cfg(test)]
+mod tests;
+
+// CONSTANTS
+// ================================================================================================
+
+const DIGEST32_BYTES: usize = 32;
+const DIGEST24_BYTES: usize = 24;
+const DIGEST20_BYTES: usize = 20;
+
+// BLAKE3 N-BIT OUTPUT
+// ================================================================================================
+
+/// N-bytes output of a blake3 function.
+///
+/// Note: `N` can't be greater than `32` because [`Digest::as_bytes`] currently supports only 32
+/// bytes.
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub struct Blake3Digest<const N: usize>([u8; N]);
+
+impl<const N: usize> Default for Blake3Digest<N> {
+    fn default() -> Self {
+        Self([0; N])
+    }
+}
+
+impl<const N: usize> Deref for Blake3Digest<N> {
+    type Target = [u8];
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<const N: usize> From<Blake3Digest<N>> for [u8; N] {
+    fn from(value: Blake3Digest<N>) -> Self {
+        value.0
+    }
+}
+
+impl<const N: usize> From<[u8; N]> for Blake3Digest<N> {
+    fn from(value: [u8; N]) -> Self {
+        Self(value)
+    }
+}
+
+impl<const N: usize> Serializable for Blake3Digest<N> {
+    fn write_into<W: ByteWriter>(&self, target: &mut W) {
+        target.write_u8_slice(&self.0);
+    }
+}
+
+impl<const N: usize> Deserializable for Blake3Digest<N> {
+    fn read_from<R: ByteReader>(source: &mut R) -> Result<Self, DeserializationError> {
+        source.read_u8_array().map(Self)
+    }
+}
+
+impl<const N: usize> Digest for Blake3Digest<N> {
+    fn as_bytes(&self) -> [u8; 32] {
+        // compile-time assertion
+        assert!(N <= 32, "digest currently supports only 32 bytes!");
+        expand_bytes(&self.0)
+    }
+}
+
+// BLAKE3 256-BIT OUTPUT
+// ================================================================================================
+
+/// 256-bit output blake3 hasher.
+pub struct Blake3_256;
+
+impl Hasher for Blake3_256 {
+    type Digest = Blake3Digest<32>;
+
+    fn hash(bytes: &[u8]) -> Self::Digest {
+        Blake3Digest(blake3::hash(bytes).into())
+    }
+
+    fn merge(values: &[Self::Digest; 2]) -> Self::Digest {
+        Self::hash(prepare_merge(values))
+    }
+
+    fn merge_with_int(seed: Self::Digest, value: u64) -> Self::Digest {
+        let mut hasher = blake3::Hasher::new();
+        hasher.update(&seed.0);
+        hasher.update(&value.to_le_bytes());
+        Blake3Digest(hasher.finalize().into())
+    }
+}
+
+impl ElementHasher for Blake3_256 {
+    type BaseField = Felt;
+
+    fn hash_elements<E>(elements: &[E]) -> Self::Digest
+    where
+        E: FieldElement<BaseField = Self::BaseField>,
+    {
+        Blake3Digest(hash_elements(elements))
+    }
+}
+
+impl Blake3_256 {
+    /// Returns a hash of the provided sequence of bytes.
+    #[inline(always)]
+    pub fn hash(bytes: &[u8]) -> Blake3Digest<DIGEST32_BYTES> {
+        <Self as Hasher>::hash(bytes)
+    }
+
+    /// Returns a hash of two digests. This method is intended for use in construction of
+    /// Merkle trees and verification of Merkle paths.
+    #[inline(always)]
+    pub fn merge(values: &[Blake3Digest<DIGEST32_BYTES>; 2]) -> Blake3Digest<DIGEST32_BYTES> {
+        <Self as Hasher>::merge(values)
+    }
+
+    /// Returns a hash of the provided field elements.
+    #[inline(always)]
+    pub fn hash_elements<E>(elements: &[E]) -> Blake3Digest<DIGEST32_BYTES>
+    where
+        E: FieldElement<BaseField = Felt>,
+    {
+        <Self as ElementHasher>::hash_elements(elements)
+    }
+}
+
+// BLAKE3 192-BIT OUTPUT
+// ================================================================================================
+
+/// 192-bit output blake3 hasher.
+pub struct Blake3_192;
+
+impl Hasher for Blake3_192 {
+    type Digest = Blake3Digest<24>;
+
+    fn hash(bytes: &[u8]) -> Self::Digest {
+        Blake3Digest(*shrink_bytes(&blake3::hash(bytes).into()))
+    }
+
+    fn merge(values: &[Self::Digest; 2]) -> Self::Digest {
+        Self::hash(prepare_merge(values))
+    }
+
+    fn merge_with_int(seed: Self::Digest, value: u64) -> Self::Digest {
+        let mut hasher = blake3::Hasher::new();
+        hasher.update(&seed.0);
+        hasher.update(&value.to_le_bytes());
+        Blake3Digest(*shrink_bytes(&hasher.finalize().into()))
+    }
+}
+
+impl ElementHasher for Blake3_192 {
+    type BaseField = Felt;
+
+    fn hash_elements<E>(elements: &[E]) -> Self::Digest
+    where
+        E: FieldElement<BaseField = Self::BaseField>,
+    {
+        Blake3Digest(hash_elements(elements))
+    }
+}
+
+impl Blake3_192 {
+    /// Returns a hash of the provided sequence of bytes.
+    #[inline(always)]
+    pub fn hash(bytes: &[u8]) -> Blake3Digest<DIGEST24_BYTES> {
+        <Self as Hasher>::hash(bytes)
+    }
+
+    /// Returns a hash of two digests. This method is intended for use in construction of
+    /// Merkle trees and verification of Merkle paths.
+    #[inline(always)]
+    pub fn merge(values: &[Blake3Digest<DIGEST24_BYTES>; 2]) -> Blake3Digest<DIGEST24_BYTES> {
+        <Self as Hasher>::merge(values)
+    }
+
+    /// Returns a hash of the provided field elements.
+    #[inline(always)]
+    pub fn hash_elements<E>(elements: &[E]) -> Blake3Digest<DIGEST24_BYTES>
+    where
+        E: FieldElement<BaseField = Felt>,
+    {
+        <Self as ElementHasher>::hash_elements(elements)
+    }
+}
+
+// BLAKE3 160-BIT OUTPUT
+// ================================================================================================
+
+/// 160-bit output blake3 hasher.
+pub struct Blake3_160;
+
+impl Hasher for Blake3_160 {
+    type Digest = Blake3Digest<20>;
+
+    fn hash(bytes: &[u8]) -> Self::Digest {
+        Blake3Digest(*shrink_bytes(&blake3::hash(bytes).into()))
+    }
+
+    fn merge(values: &[Self::Digest; 2]) -> Self::Digest {
+        Self::hash(prepare_merge(values))
+    }
+
+    fn merge_with_int(seed: Self::Digest, value: u64) -> Self::Digest {
+        let mut hasher = blake3::Hasher::new();
+        hasher.update(&seed.0);
+        hasher.update(&value.to_le_bytes());
+        Blake3Digest(*shrink_bytes(&hasher.finalize().into()))
+    }
+}
+
+impl ElementHasher for Blake3_160 {
+    type BaseField = Felt;
+
+    fn hash_elements<E>(elements: &[E]) -> Self::Digest
+    where
+        E: FieldElement<BaseField = Self::BaseField>,
+    {
+        Blake3Digest(hash_elements(elements))
+    }
+}
+
+impl Blake3_160 {
+    /// Returns a hash of the provided sequence of bytes.
+    #[inline(always)]
+    pub fn hash(bytes: &[u8]) -> Blake3Digest<DIGEST20_BYTES> {
+        <Self as Hasher>::hash(bytes)
+    }
+
+    /// Returns a hash of two digests. This method is intended for use in construction of
+    /// Merkle trees and verification of Merkle paths.
+    #[inline(always)]
+    pub fn merge(values: &[Blake3Digest<DIGEST20_BYTES>; 2]) -> Blake3Digest<DIGEST20_BYTES> {
+        <Self as Hasher>::merge(values)
+    }
+
+    /// Returns a hash of the provided field elements.
+    #[inline(always)]
+    pub fn hash_elements<E>(elements: &[E]) -> Blake3Digest<DIGEST20_BYTES>
+    where
+        E: FieldElement<BaseField = Felt>,
+    {
+        <Self as ElementHasher>::hash_elements(elements)
+    }
+}
+
+// HELPER FUNCTIONS
+// ================================================================================================
+
+/// Zero-copy ref shrink to array.
+fn shrink_bytes<const M: usize, const N: usize>(bytes: &[u8; M]) -> &[u8; N] {
+    // compile-time assertion
+    assert!(
+        M >= N,
+        "N should fit in M so it can be safely transmuted into a smaller slice!"
+    );
+    // safety: bytes len is asserted
+    unsafe { transmute(bytes) }
+}
+
+/// Hash the elements into bytes and shrink the output.
+fn hash_elements<const N: usize, E>(elements: &[E]) -> [u8; N]
+where
+    E: FieldElement<BaseField = Felt>,
+{
+    // don't leak assumptions from felt and check its actual implementation.
+    // this is a compile-time branch so it is for free
+    let digest = if Felt::IS_CANONICAL {
+        blake3::hash(E::elements_as_bytes(elements))
+    } else {
+        E::as_base_elements(elements)
+            .iter()
+            .fold(blake3::Hasher::new(), |mut hasher, felt| {
+                hasher.update(&felt.as_int().to_le_bytes());
+                hasher
+            })
+            .finalize()
+    };
+    *shrink_bytes(&digest.into())
+}
+
+/// Owned bytes expansion.
+fn expand_bytes<const M: usize, const N: usize>(bytes: &[u8; M]) -> [u8; N] {
+    // compile-time assertion
+    assert!(M <= N, "M should fit in N so M can be expanded!");
+    // this branch is constant so it will be optimized to be either one of the variants in release
+    // mode
+    if M == N {
+        // safety: the sizes are checked to be the same
+        unsafe { transmute_copy(bytes) }
+    } else {
+        let mut expanded = [0u8; N];
+        expanded[..M].copy_from_slice(bytes);
+        expanded
+    }
+}
+
+// Cast the slice into contiguous bytes.
+fn prepare_merge<const N: usize, D>(args: &[D; N]) -> &[u8]
+where
+    D: Deref<Target = [u8]>,
+{
+    // compile-time assertion
+    assert!(N > 0, "N shouldn't represent an empty slice!");
+    let values = args.as_ptr() as *const u8;
+    let len = size_of::<D>() * N;
+    // safety: the values are tested to be contiguous
+    let bytes = unsafe { from_raw_parts(values, len) };
+    debug_assert_eq!(args[0].deref(), &bytes[..len / N]);
+    bytes
+}

src/hash/blake/tests.rs

@@ -0,0 +1,20 @@
+use super::*;
+use crate::utils::collections::Vec;
+use proptest::prelude::*;
+
+proptest! {
+    #[test]
+    fn blake160_wont_panic_with_arbitrary_input(ref vec in any::<Vec<u8>>()) {
+        Blake3_160::hash(vec);
+    }
+
+    #[test]
+    fn blake192_wont_panic_with_arbitrary_input(ref vec in any::<Vec<u8>>()) {
+        Blake3_192::hash(vec);
+    }
+
+    #[test]
+    fn blake256_wont_panic_with_arbitrary_input(ref vec in any::<Vec<u8>>()) {
+        Blake3_256::hash(vec);
+    }
+}

src/hash/mod.rs

@@ -1,18 +1,5 @@
-use crate::{ElementHasher, HashFn};
+use super::{Felt, FieldElement, StarkField, ONE, ZERO};
+use winter_crypto::{Digest, ElementHasher, Hasher};
 
-mod rpo;
-pub use rpo::Rpo256 as Hasher;
-pub use rpo::{INV_MDS, MDS};
-
-// TYPE ALIASES
-// ================================================================================================
-
-pub type Digest = <Hasher as HashFn>::Digest;
-
-// HELPER FUNCTIONS
-// ================================================================================================
-
-#[inline(always)]
-pub fn merge(values: &[Digest; 2]) -> Digest {
-    Hasher::merge(values)
-}
+pub mod blake;
+pub mod rpo;

src/hash/rpo/digest.rs

@@ -1,17 +1,16 @@
-use super::DIGEST_SIZE;
-use crate::{
-    ByteReader, ByteWriter, Deserializable, DeserializationError, Digest, Felt, Serializable,
-    StarkField, ZERO,
+use super::{Digest, Felt, StarkField, DIGEST_SIZE, ZERO};
+use crate::utils::{
+    string::String, ByteReader, ByteWriter, Deserializable, DeserializationError, Serializable,
 };
-use core::ops::Deref;
+use core::{cmp::Ordering, ops::Deref};
 
 // DIGEST TRAIT IMPLEMENTATIONS
 // ================================================================================================
 
-#[derive(Debug, Copy, Clone, Eq, PartialEq)]
-pub struct RpoDigest256([Felt; DIGEST_SIZE]);
+#[derive(Debug, Default, Copy, Clone, Eq, PartialEq)]
+pub struct RpoDigest([Felt; DIGEST_SIZE]);
 
-impl RpoDigest256 {
+impl RpoDigest {
     pub fn new(value: [Felt; DIGEST_SIZE]) -> Self {
         Self(value)
     }
@@ -20,6 +19,10 @@ impl RpoDigest256 {
         self.as_ref()
     }
 
+    pub fn as_bytes(&self) -> [u8; 32] {
+        <Self as Digest>::as_bytes(self)
+    }
+
     pub fn digests_as_elements<'a, I>(digests: I) -> impl Iterator<Item = &'a Felt>
     where
         I: Iterator<Item = &'a Self>,
@@ -28,7 +31,7 @@ impl RpoDigest256 {
     }
 }
 
-impl Digest for RpoDigest256 {
+impl Digest for RpoDigest {
     fn as_bytes(&self) -> [u8; 32] {
         let mut result = [0; 32];
 
@@ -41,27 +44,21 @@ impl Digest for RpoDigest256 {
     }
 }
 
-impl Default for RpoDigest256 {
-    fn default() -> Self {
-        RpoDigest256([Felt::default(); DIGEST_SIZE])
-    }
-}
-
-impl Serializable for RpoDigest256 {
+impl Serializable for RpoDigest {
     fn write_into<W: ByteWriter>(&self, target: &mut W) {
         target.write_u8_slice(&self.as_bytes());
     }
 }
 
-impl Deserializable for RpoDigest256 {
+impl Deserializable for RpoDigest {
     fn read_from<R: ByteReader>(source: &mut R) -> Result<Self, DeserializationError> {
         let mut inner: [Felt; DIGEST_SIZE] = [ZERO; DIGEST_SIZE];
         for inner in inner.iter_mut() {
             let e = source.read_u64()?;
             if e >= Felt::MODULUS {
-                return Err(DeserializationError::InvalidValue(
-                    "Value not in the appropriate range".to_owned(),
-                ));
+                return Err(DeserializationError::InvalidValue(String::from(
+                    "Value not in the appropriate range",
+                )));
             }
             *inner = Felt::new(e);
         }
@@ -70,25 +67,25 @@ impl Deserializable for RpoDigest256 {
     }
 }
 
-impl From<[Felt; DIGEST_SIZE]> for RpoDigest256 {
+impl From<[Felt; DIGEST_SIZE]> for RpoDigest {
     fn from(value: [Felt; DIGEST_SIZE]) -> Self {
         Self(value)
     }
 }
 
-impl From<RpoDigest256> for [Felt; DIGEST_SIZE] {
-    fn from(value: RpoDigest256) -> Self {
+impl From<RpoDigest> for [Felt; DIGEST_SIZE] {
+    fn from(value: RpoDigest) -> Self {
         value.0
     }
 }
 
-impl From<RpoDigest256> for [u8; 32] {
-    fn from(value: RpoDigest256) -> Self {
+impl From<RpoDigest> for [u8; 32] {
+    fn from(value: RpoDigest) -> Self {
         value.as_bytes()
     }
 }
 
-impl Deref for RpoDigest256 {
+impl Deref for RpoDigest {
     type Target = [Felt; DIGEST_SIZE];
 
     fn deref(&self) -> &Self::Target {
@@ -96,14 +93,44 @@ impl Deref for RpoDigest256 {
     }
 }
 
+impl Ord for RpoDigest {
+    fn cmp(&self, other: &Self) -> Ordering {
+        // compare the inner u64 of both elements.
+        //
+        // it will iterate the elements and will return the first computation different than
+        // `Equal`. Otherwise, the ordering is equal.
+        //
+        // the endianness is irrelevant here because since, this being a cryptographically secure
+        // hash computation, the digest shouldn't have any ordered property of its input.
+        //
+        // finally, we use `Felt::inner` instead of `Felt::as_int` so we avoid performing a
+        // montgomery reduction for every limb. that is safe because every inner element of the
+        // digest is guaranteed to be in its canonical form (that is, `x in [0,p)`).
+        self.0
+            .iter()
+            .map(Felt::inner)
+            .zip(other.0.iter().map(Felt::inner))
+            .fold(Ordering::Equal, |ord, (a, b)| match ord {
+                Ordering::Equal => a.cmp(&b),
+                _ => ord,
+            })
+    }
+}
+
+impl PartialOrd for RpoDigest {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
 // TESTS
 // ================================================================================================
 
 #[cfg(test)]
 mod tests {
 
-    use super::RpoDigest256;
-    use crate::{Deserializable, Felt, Serializable, SliceReader};
+    use super::{Deserializable, Felt, RpoDigest, Serializable};
+    use crate::utils::SliceReader;
     use rand_utils::rand_value;
 
     #[test]
@@ -113,14 +140,14 @@ mod tests {
         let e3 = Felt::new(rand_value());
         let e4 = Felt::new(rand_value());
 
-        let d1 = RpoDigest256([e1, e2, e3, e4]);
+        let d1 = RpoDigest([e1, e2, e3, e4]);
 
         let mut bytes = vec![];
         d1.write_into(&mut bytes);
         assert_eq!(32, bytes.len());
 
         let mut reader = SliceReader::new(&bytes);
-        let d2 = RpoDigest256::read_from(&mut reader).unwrap();
+        let d2 = RpoDigest::read_from(&mut reader).unwrap();
 
         assert_eq!(d1, d2);
     }

src/hash/rpo/mds_freq.rs

@@ -156,9 +156,7 @@ const fn block3(x: [i64; 3], y: [i64; 3]) -> [i64; 3] {
 
 #[cfg(test)]
 mod tests {
-    use super::super::Rpo256;
-    use crate::hash::rpo::MDS;
-    use crate::{Felt, FieldElement};
+    use super::super::{Felt, FieldElement, Rpo256, MDS};
     use proptest::prelude::*;
 
     const STATE_WIDTH: usize = 12;

src/hash/rpo/mod.rs

@@ -1,9 +1,8 @@
-use super::{ElementHasher, HashFn};
-use crate::{Felt, FieldElement, StarkField, ONE, ZERO};
+use super::{Digest, ElementHasher, Felt, FieldElement, Hasher, StarkField, ONE, ZERO};
 use core::{convert::TryInto, ops::Range};
 
 mod digest;
-pub use digest::RpoDigest256;
+pub use digest::RpoDigest;
 
 mod mds_freq;
 use mds_freq::mds_multiply_freq;
@@ -53,10 +52,10 @@ const INV_ALPHA: u64 = 10540996611094048183;
 // HASHER IMPLEMENTATION
 // ================================================================================================
 
-/// Implementation of [Hasher] trait for Rescue Prime Optimized (Rpo256) hash function with 256-bit output.
+/// Implementation of the Rescue Prime Optimized hash function with 256-bit output.
 ///
 /// The hash function is implemented according to the Rescue Prime Optimized
-/// [specifications](https://github.com/ASDiscreteMathematics/rpo)
+/// [specifications](https://eprint.iacr.org/2022/1577)
 ///
 /// The parameters used to instantiate the function are:
 /// * Field: 64-bit prime field with modulus 2^64 - 2^32 + 1.
@@ -91,8 +90,8 @@ const INV_ALPHA: u64 = 10540996611094048183;
 /// using [hash()](Rpo256::hash) function.
 pub struct Rpo256();
 
-impl HashFn for Rpo256 {
-    type Digest = RpoDigest256;
+impl Hasher for Rpo256 {
+    type Digest = RpoDigest;
 
     fn hash(bytes: &[u8]) -> Self::Digest {
         // compute the number of elements required to represent the string; we will be processing
@@ -150,7 +149,7 @@ impl HashFn for Rpo256 {
         }
 
         // return the first 4 elements of the state as hash result
-        RpoDigest256::new(state[DIGEST_RANGE].try_into().unwrap())
+        RpoDigest::new(state[DIGEST_RANGE].try_into().unwrap())
     }
 
     fn merge(values: &[Self::Digest; 2]) -> Self::Digest {
@@ -164,7 +163,7 @@ impl HashFn for Rpo256 {
 
         // apply the RPO permutation and return the first four elements of the state
         Self::apply_permutation(&mut state);
-        RpoDigest256::new(state[DIGEST_RANGE].try_into().unwrap())
+        RpoDigest::new(state[DIGEST_RANGE].try_into().unwrap())
     }
 
     fn merge_with_int(seed: Self::Digest, value: u64) -> Self::Digest {
@@ -191,7 +190,7 @@ impl HashFn for Rpo256 {
 
         // apply the RPO permutation and return the first four elements of the state
         Self::apply_permutation(&mut state);
-        RpoDigest256::new(state[DIGEST_RANGE].try_into().unwrap())
+        RpoDigest::new(state[DIGEST_RANGE].try_into().unwrap())
     }
 }
 
@@ -237,7 +236,7 @@ impl ElementHasher for Rpo256 {
         }
 
         // return the first 4 elements of the state as hash result
-        RpoDigest256::new(state[DIGEST_RANGE].try_into().unwrap())
+        RpoDigest::new(state[DIGEST_RANGE].try_into().unwrap())
     }
 }
 
@@ -245,10 +244,61 @@ impl ElementHasher for Rpo256 {
 // ================================================================================================
 
 impl Rpo256 {
+    // CONSTANTS
+    // --------------------------------------------------------------------------------------------
+
+    /// The number of rounds is set to 7 to target 128-bit security level.
+    pub const NUM_ROUNDS: usize = NUM_ROUNDS;
+
+    /// Sponge state is set to 12 field elements or 768 bytes; 8 elements are reserved for rate and
+    /// the remaining 4 elements are reserved for capacity.
+    pub const STATE_WIDTH: usize = STATE_WIDTH;
+
+    /// The rate portion of the state is located in elements 4 through 11 (inclusive).
+    pub const RATE_RANGE: Range<usize> = RATE_RANGE;
+
+    /// The capacity portion of the state is located in elements 0, 1, 2, and 3.
+    pub const CAPACITY_RANGE: Range<usize> = CAPACITY_RANGE;
+
+    /// The output of the hash function can be read from state elements 4, 5, 6, and 7.
+    pub const DIGEST_RANGE: Range<usize> = DIGEST_RANGE;
+
+    /// MDS matrix used for computing the linear layer in a RPO round.
+    pub const MDS: [[Felt; STATE_WIDTH]; STATE_WIDTH] = MDS;
+
+    /// Round constants added to the hasher state in the first half of the RPO round.
+    pub const ARK1: [[Felt; STATE_WIDTH]; NUM_ROUNDS] = ARK1;
+
+    /// Round constants added to the hasher state in the second half of the RPO round.
+    pub const ARK2: [[Felt; STATE_WIDTH]; NUM_ROUNDS] = ARK2;
+
+    // TRAIT PASS-THROUGH FUNCTIONS
+    // --------------------------------------------------------------------------------------------
+
+    /// Returns a hash of the provided sequence of bytes.
+    #[inline(always)]
+    pub fn hash(bytes: &[u8]) -> RpoDigest {
+        <Self as Hasher>::hash(bytes)
+    }
+
+    /// Returns a hash of two digests. This method is intended for use in construction of
+    /// Merkle trees and verification of Merkle paths.
+    #[inline(always)]
+    pub fn merge(values: &[RpoDigest; 2]) -> RpoDigest {
+        <Self as Hasher>::merge(values)
+    }
+
+    /// Returns a hash of the provided field elements.
+    #[inline(always)]
+    pub fn hash_elements<E: FieldElement<BaseField = Felt>>(elements: &[E]) -> RpoDigest {
+        <Self as ElementHasher>::hash_elements(elements)
+    }
+
     // RESCUE PERMUTATION
     // --------------------------------------------------------------------------------------------
 
     /// Applies RPO permutation to the provided state.
+    #[inline(always)]
     pub fn apply_permutation(state: &mut [Felt; STATE_WIDTH]) {
         for i in 0..NUM_ROUNDS {
             Self::apply_round(state, i);
@@ -378,7 +428,7 @@ impl Rpo256 {
 // MDS
 // ================================================================================================
 /// RPO MDS matrix
-pub const MDS: [[Felt; STATE_WIDTH]; STATE_WIDTH] = [
+const MDS: [[Felt; STATE_WIDTH]; STATE_WIDTH] = [
     [
         Felt::new(7),
         Felt::new(23),
@@ -549,178 +599,6 @@ pub const MDS: [[Felt; STATE_WIDTH]; STATE_WIDTH] = [
     ],
 ];
 
-/// RPO Inverse MDS matrix
-pub const INV_MDS: [[Felt; STATE_WIDTH]; STATE_WIDTH] = [
-    [
-        Felt::new(14868391535953158196),
-        Felt::new(13278298489594233127),
-        Felt::new(389999932707070822),
-        Felt::new(9782021734907796003),
-        Felt::new(4829905704463175582),
-        Felt::new(7567822018949214430),
-        Felt::new(14205019324568680367),
-        Felt::new(15489674211196160593),
-        Felt::new(17636013826542227504),
-        Felt::new(16254215311946436093),
-        Felt::new(3641486184877122796),
-        Felt::new(11069068059762973582),
-    ],
-    [
-        Felt::new(11069068059762973582),
-        Felt::new(14868391535953158196),
-        Felt::new(13278298489594233127),
-        Felt::new(389999932707070822),
-        Felt::new(9782021734907796003),
-        Felt::new(4829905704463175582),
-        Felt::new(7567822018949214430),
-        Felt::new(14205019324568680367),
-        Felt::new(15489674211196160593),
-        Felt::new(17636013826542227504),
-        Felt::new(16254215311946436093),
-        Felt::new(3641486184877122796),
-    ],
-    [
-        Felt::new(3641486184877122796),
-        Felt::new(11069068059762973582),
-        Felt::new(14868391535953158196),
-        Felt::new(13278298489594233127),
-        Felt::new(389999932707070822),
-        Felt::new(9782021734907796003),
-        Felt::new(4829905704463175582),
-        Felt::new(7567822018949214430),
-        Felt::new(14205019324568680367),
-        Felt::new(15489674211196160593),
-        Felt::new(17636013826542227504),
-        Felt::new(16254215311946436093),
-    ],
-    [
-        Felt::new(16254215311946436093),
-        Felt::new(3641486184877122796),
-        Felt::new(11069068059762973582),
-        Felt::new(14868391535953158196),
-        Felt::new(13278298489594233127),
-        Felt::new(389999932707070822),
-        Felt::new(9782021734907796003),
-        Felt::new(4829905704463175582),
-        Felt::new(7567822018949214430),
-        Felt::new(14205019324568680367),
-        Felt::new(15489674211196160593),
-        Felt::new(17636013826542227504),
-    ],
-    [
-        Felt::new(17636013826542227504),
-        Felt::new(16254215311946436093),
-        Felt::new(3641486184877122796),
-        Felt::new(11069068059762973582),
-        Felt::new(14868391535953158196),
-        Felt::new(13278298489594233127),
-        Felt::new(389999932707070822),
-        Felt::new(9782021734907796003),
-        Felt::new(4829905704463175582),
-        Felt::new(7567822018949214430),
-        Felt::new(14205019324568680367),
-        Felt::new(15489674211196160593),
-    ],
-    [
-        Felt::new(15489674211196160593),
-        Felt::new(17636013826542227504),
-        Felt::new(16254215311946436093),
-        Felt::new(3641486184877122796),
-        Felt::new(11069068059762973582),
-        Felt::new(14868391535953158196),
-        Felt::new(13278298489594233127),
-        Felt::new(389999932707070822),
-        Felt::new(9782021734907796003),
-        Felt::new(4829905704463175582),
-        Felt::new(7567822018949214430),
-        Felt::new(14205019324568680367),
-    ],
-    [
-        Felt::new(14205019324568680367),
-        Felt::new(15489674211196160593),
-        Felt::new(17636013826542227504),
-        Felt::new(16254215311946436093),
-        Felt::new(3641486184877122796),
-        Felt::new(11069068059762973582),
-        Felt::new(14868391535953158196),
-        Felt::new(13278298489594233127),
-        Felt::new(389999932707070822),
-        Felt::new(9782021734907796003),
-        Felt::new(4829905704463175582),
-        Felt::new(7567822018949214430),
-    ],
-    [
-        Felt::new(7567822018949214430),
-        Felt::new(14205019324568680367),
-        Felt::new(15489674211196160593),
-        Felt::new(17636013826542227504),
-        Felt::new(16254215311946436093),
-        Felt::new(3641486184877122796),
-        Felt::new(11069068059762973582),
-        Felt::new(14868391535953158196),
-        Felt::new(13278298489594233127),
-        Felt::new(389999932707070822),
-        Felt::new(9782021734907796003),
-        Felt::new(4829905704463175582),
-    ],
-    [
-        Felt::new(4829905704463175582),
-        Felt::new(7567822018949214430),
-        Felt::new(14205019324568680367),
-        Felt::new(15489674211196160593),
-        Felt::new(17636013826542227504),
-        Felt::new(16254215311946436093),
-        Felt::new(3641486184877122796),
-        Felt::new(11069068059762973582),
-        Felt::new(14868391535953158196),
-        Felt::new(13278298489594233127),
-        Felt::new(389999932707070822),
-        Felt::new(9782021734907796003),
-    ],
-    [
-        Felt::new(9782021734907796003),
-        Felt::new(4829905704463175582),
-        Felt::new(7567822018949214430),
-        Felt::new(14205019324568680367),
-        Felt::new(15489674211196160593),
-        Felt::new(17636013826542227504),
-        Felt::new(16254215311946436093),
-        Felt::new(3641486184877122796),
-        Felt::new(11069068059762973582),
-        Felt::new(14868391535953158196),
-        Felt::new(13278298489594233127),
-        Felt::new(389999932707070822),
-    ],
-    [
-        Felt::new(389999932707070822),
-        Felt::new(9782021734907796003),
-        Felt::new(4829905704463175582),
-        Felt::new(7567822018949214430),
-        Felt::new(14205019324568680367),
-        Felt::new(15489674211196160593),
-        Felt::new(17636013826542227504),
-        Felt::new(16254215311946436093),
-        Felt::new(3641486184877122796),
-        Felt::new(11069068059762973582),
-        Felt::new(14868391535953158196),
-        Felt::new(13278298489594233127),
-    ],
-    [
-        Felt::new(13278298489594233127),
-        Felt::new(389999932707070822),
-        Felt::new(9782021734907796003),
-        Felt::new(4829905704463175582),
-        Felt::new(7567822018949214430),
-        Felt::new(14205019324568680367),
-        Felt::new(15489674211196160593),
-        Felt::new(17636013826542227504),
-        Felt::new(16254215311946436093),
-        Felt::new(3641486184877122796),
-        Felt::new(11069068059762973582),
-        Felt::new(14868391535953158196),
-    ],
-];
-
 // ROUND CONSTANTS
 // ================================================================================================
 

src/hash/rpo/tests.rs

@@ -1,32 +1,9 @@
 use super::{
-    ElementHasher, Felt, FieldElement, HashFn, Rpo256, RpoDigest256, StarkField, ALPHA, INV_ALPHA,
-    INV_MDS, MDS, STATE_WIDTH, ZERO,
+    Felt, FieldElement, Hasher, Rpo256, RpoDigest, StarkField, ALPHA, INV_ALPHA, STATE_WIDTH, ZERO,
 };
 use core::convert::TryInto;
 use rand_utils::rand_value;
 
-#[test]
-#[allow(clippy::needless_range_loop)]
-fn mds_inv_test() {
-    let mut mul_result = [[Felt::new(0); STATE_WIDTH]; STATE_WIDTH];
-    for i in 0..STATE_WIDTH {
-        for j in 0..STATE_WIDTH {
-            let result = {
-                let mut result = Felt::new(0);
-                for k in 0..STATE_WIDTH {
-                    result += MDS[i][k] * INV_MDS[k][j]
-                }
-                result
-            };
-            mul_result[i][j] = result;
-            if i == j {
-                assert_eq!(result, Felt::new(1));
-            } else {
-                assert_eq!(result, Felt::new(0));
-            }
-        }
-    }
-}
 #[test]
 fn test_alphas() {
     let e: Felt = Felt::new(rand_value());
@@ -64,9 +41,9 @@ fn test_inv_sbox() {
 fn hash_elements_vs_merge() {
     let elements = [Felt::new(rand_value()); 8];
 
-    let digests: [RpoDigest256; 2] = [
-        RpoDigest256::new(elements[..4].try_into().unwrap()),
-        RpoDigest256::new(elements[4..].try_into().unwrap()),
+    let digests: [RpoDigest; 2] = [
+        RpoDigest::new(elements[..4].try_into().unwrap()),
+        RpoDigest::new(elements[4..].try_into().unwrap()),
     ];
 
     let m_result = Rpo256::merge(&digests);
@@ -77,7 +54,7 @@ fn hash_elements_vs_merge() {
 #[test]
 fn hash_elements_vs_merge_with_int() {
     let tmp = [Felt::new(rand_value()); 4];
-    let seed = RpoDigest256::new(tmp);
+    let seed = RpoDigest::new(tmp);
 
     // ----- value fits into a field element ------------------------------------------------------
     let val: Felt = Felt::new(rand_value());
@@ -147,9 +124,9 @@ fn hash_elements() {
         Felt::new(7),
     ];
 
-    let digests: [RpoDigest256; 2] = [
-        RpoDigest256::new(elements[..4].try_into().unwrap()),
-        RpoDigest256::new(elements[4..8].try_into().unwrap()),
+    let digests: [RpoDigest; 2] = [
+        RpoDigest::new(elements[..4].try_into().unwrap()),
+        RpoDigest::new(elements[4..8].try_into().unwrap()),
     ];
 
     let m_result = Rpo256::merge(&digests);
@@ -182,7 +159,7 @@ fn hash_test_vectors() {
     ];
 
     for i in 0..elements.len() {
-        let expected = RpoDigest256::new(EXPECTED[i]);
+        let expected = RpoDigest::new(EXPECTED[i]);
         let result = Rpo256::hash_elements(&elements[..(i + 1)]);
         assert_eq!(result, expected);
     }

src/lib.rs

@@ -1,27 +1,35 @@
-pub use winter_crypto::{Digest, ElementHasher, Hasher as HashFn};
-pub use winter_math::{
-    fields::{f64::BaseElement as Felt, QuadExtension},
-    log2, ExtensionOf, FieldElement, StarkField,
-};
-pub use winter_utils::{
-    collections::{BTreeMap, Vec},
-    uninit_vector, ByteReader, ByteWriter, Deserializable, DeserializationError, Serializable,
-    SliceReader,
-};
+#![cfg_attr(not(feature = "std"), no_std)]
+
+#[cfg(not(feature = "std"))]
+#[cfg_attr(test, macro_use)]
+extern crate alloc;
 
 pub mod hash;
 pub mod merkle;
 
+// RE-EXPORTS
+// ================================================================================================
+
+pub use winter_math::{fields::f64::BaseElement as Felt, FieldElement, StarkField};
+
+pub mod utils {
+    pub use winter_utils::{
+        collections, string, uninit_vector, ByteReader, ByteWriter, Deserializable,
+        DeserializationError, Serializable, SliceReader,
+    };
+}
+
 // TYPE ALIASES
 // ================================================================================================
 
+/// A group of four field elements in the Miden base field.
 pub type Word = [Felt; 4];
 
 // CONSTANTS
 // ================================================================================================
 
-/// Field element representing ZERO in the base field of the VM.
+/// Field element representing ZERO in the Miden base filed.
 pub const ZERO: Felt = Felt::ZERO;
 
-/// Field element representing ONE in the base field of the VM.
+/// Field element representing ONE in the Miden base filed.
 pub const ONE: Felt = Felt::ONE;

src/merkle/merkle_path_set.rs

@@ -1,12 +1,9 @@
-use super::{MerkleError, Word};
-use crate::{hash::merge, BTreeMap, Vec, ZERO};
+use super::{BTreeMap, MerkleError, Rpo256, Vec, Word, ZERO};
 
 // MERKLE PATH SET
 // ================================================================================================
 
 /// A set of Merkle paths.
-///
-/// This struct is intended to be used as one of the variants of the MerkleSet enum.
 #[derive(Clone, Debug)]
 pub struct MerklePathSet {
     root: Word,
@@ -57,7 +54,7 @@ impl MerklePathSet {
         let pos = 2u64.pow(self.total_depth) + index;
 
         // Index of the leaf path in map. Paths of neighboring leaves are stored in one key-value pair
-        let half_pos = (pos / 2) as u64;
+        let half_pos = pos / 2;
 
         let mut extended_path = path;
         if is_even(pos) {
@@ -104,7 +101,7 @@ impl MerklePathSet {
         }
 
         let pos = 2u64.pow(depth) + index;
-        let index = (pos / 2) as u64;
+        let index = pos / 2;
 
         match self.paths.get(&index) {
             None => Err(MerkleError::NodeNotInSet(index)),
@@ -208,9 +205,9 @@ fn is_even(pos: u64) -> bool {
 /// - sibling — neighboring vertex in the tree
 fn calculate_parent_hash(node: Word, node_pos: u64, sibling: Word) -> Word {
     if is_even(node_pos) {
-        merge(&[node.into(), sibling.into()]).into()
+        Rpo256::merge(&[node.into(), sibling.into()]).into()
     } else {
-        merge(&[sibling.into(), node.into()]).into()
+        Rpo256::merge(&[sibling.into(), node.into()]).into()
     }
 }
 
@@ -220,7 +217,7 @@ fn compute_path_trace(path: &[Word], depth: u32, index: u64) -> (Vec<Word>, Word
 
     let mut computed_hashes = Vec::<Word>::new();
 
-    let mut comp_hash = merge(&[path[0].into(), path[1].into()]).into();
+    let mut comp_hash = Rpo256::merge(&[path[0].into(), path[1].into()]).into();
 
     if path.len() != 2 {
         for path_hash in path.iter().skip(2) {
@@ -238,7 +235,7 @@ fn compute_path_root(path: &[Word], depth: u32, index: u64) -> Word {
     let mut pos = 2u64.pow(depth) + index;
 
     // hash that is obtained after calculating the current hash and path hash
-    let mut comp_hash = merge(&[path[0].into(), path[1].into()]).into();
+    let mut comp_hash = Rpo256::merge(&[path[0].into(), path[1].into()]).into();
 
     for path_hash in path.iter().skip(2) {
         pos /= 2;

src/merkle/merkle_tree.rs

@@ -1,16 +1,12 @@
-use super::MerkleError;
-use crate::{
-    hash::{merge, Digest},
-    log2, uninit_vector, Felt, FieldElement, Word,
-};
+use super::{Digest, Felt, MerkleError, Rpo256, Vec, Word};
+use crate::{utils::uninit_vector, FieldElement};
 use core::slice;
+use winter_math::log2;
 
 // MERKLE TREE
 // ================================================================================================
 
 /// A fully-balanced binary Merkle tree (i.e., a tree where the number of leaves is a power of two).
-///
-/// This struct is intended to be used as one of the variants of the MerkleSet enum.
 #[derive(Clone, Debug)]
 pub struct MerkleTree {
     nodes: Vec<Word>,
@@ -43,7 +39,7 @@ impl MerkleTree {
 
         // calculate all internal tree nodes
         for i in (1..n).rev() {
-            nodes[i] = merge(&two_nodes[i]).into();
+            nodes[i] = Rpo256::merge(&two_nodes[i]).into();
         }
 
         Ok(Self { nodes })
@@ -80,7 +76,7 @@ impl MerkleTree {
             return Err(MerkleError::InvalidIndex(depth, index));
         }
 
-        let pos = 2usize.pow(depth as u32) + (index as usize);
+        let pos = 2_usize.pow(depth) + (index as usize);
         Ok(self.nodes[pos])
     }
 
@@ -102,7 +98,7 @@ impl MerkleTree {
         }
 
         let mut path = Vec::with_capacity(depth as usize);
-        let mut pos = 2usize.pow(depth as u32) + (index as usize);
+        let mut pos = 2_usize.pow(depth) + (index as usize);
 
         while pos > 1 {
             path.push(self.nodes[pos ^ 1]);
@@ -131,7 +127,7 @@ impl MerkleTree {
 
         for _ in 0..depth {
             index /= 2;
-            self.nodes[index] = merge(&two_nodes[index]).into();
+            self.nodes[index] = Rpo256::merge(&two_nodes[index]).into();
         }
 
         Ok(())
@@ -143,7 +139,10 @@ impl MerkleTree {
 
 #[cfg(test)]
 mod tests {
-    use crate::{hash::Hasher, merkle::int_to_node, ElementHasher, HashFn, Word};
+    use super::{
+        super::{int_to_node, Rpo256},
+        Word,
+    };
 
     const LEAVES4: [Word; 4] = [
         int_to_node(1),
@@ -244,9 +243,9 @@ mod tests {
     // --------------------------------------------------------------------------------------------
 
     fn compute_internal_nodes() -> (Word, Word, Word) {
-        let node2 = Hasher::hash_elements(&[LEAVES4[0], LEAVES4[1]].concat());
-        let node3 = Hasher::hash_elements(&[LEAVES4[2], LEAVES4[3]].concat());
-        let root = Hasher::merge(&[node2, node3]);
+        let node2 = Rpo256::hash_elements(&[LEAVES4[0], LEAVES4[1]].concat());
+        let node3 = Rpo256::hash_elements(&[LEAVES4[2], LEAVES4[3]].concat());
+        let root = Rpo256::merge(&[node2, node3]);
 
         (root.into(), node2.into(), node3.into())
     }

src/merkle/mod.rs

@@ -1,10 +1,14 @@
-use crate::Word;
+use super::{
+    hash::rpo::{Rpo256, RpoDigest as Digest},
+    utils::collections::{BTreeMap, Vec},
+    Felt, Word, ZERO,
+};
 
-#[cfg(test)]
-use crate::{Felt, ZERO};
+mod merkle_tree;
+pub use merkle_tree::MerkleTree;
 
-pub mod merkle_path_set;
-pub mod merkle_tree;
+mod merkle_path_set;
+pub use merkle_path_set::MerklePathSet;
 
 // ERRORS
 // ================================================================================================