Starknet Keccak

Cargo.toml

@@ -13,6 +13,7 @@ indexmap = { version = "1.9.2", features = ["serde"] }
 once_cell = { version = "1.16.0" }
 serde = { version = "1.0.130", features = ["derive", "rc"] }
 serde_json = { version = "1.0.81" }
+sha3 = { version = "0.10.6"}
 starknet-crypto = { version = "0.2.0" }
 thiserror = { version = "1.0.31" }
 web3 = { version = "0.18.0" }

src/hash.rs

@@ -6,7 +6,9 @@ use std::fmt::{Debug, Display};
 use std::io::Error;
 
 use serde::{Deserialize, Serialize};
+use sha3::Digest;
 use starknet_crypto::{pedersen_hash as starknet_crypto_pedersen_hash, FieldElement};
+use web3::types::U256;
 
 use crate::serde_utils::{
     bytes_from_hex_str, hex_str_from_bytes, BytesAsHex, NonPrefixedBytesAsHex, PrefixedBytesAsHex,
@@ -19,6 +21,9 @@ pub const GENESIS_HASH: &str = "0x0";
 // Felt encoding constants.
 const CHOOSER_FULL: u8 = 15;
 const CHOOSER_HALF: u8 = 14;
+/// The MASK equals to U256::pow(U256::from(2), U256::from(250)) - U256::from(1)
+const MASK: U256 =
+    U256([18446744073709551615, 18446744073709551615, 18446744073709551615, 288230376151711743]);
 
 /// An alias for [`StarkFelt`].
 /// The output of the [Pedersen hash](https://docs.starknet.io/documentation/architecture_and_concepts/Hashing/hash-functions/#pedersen_hash).
@@ -43,6 +48,17 @@ pub fn pedersen_hash_array(felts: &[StarkFelt]) -> StarkHash {
     pedersen_hash(&current_hash, &data_len)
 }
 
+/// Computes Starknet Keccak Hash, as defined
+/// in <https://docs.starknet.io/documentation/architecture_and_concepts/Hashing/hash-functions/#starknet-keccak.>
+pub fn starknet_keccak(data: &[u8]) -> Result<StarkFelt, StarknetApiError> {
+    let keccak256 = sha3::Keccak256::digest(data);
+    let number = U256::from_big_endian(keccak256.as_slice());
+    let masked_number = number & MASK;
+    let mut res_bytes: [u8; 32] = [0; 32];
+    masked_number.to_big_endian(&mut res_bytes);
+    StarkFelt::new(res_bytes)
+}
+
 // TODO: Move to a different crate.
 /// The StarkNet [field element](https://docs.starknet.io/documentation/architecture_and_concepts/Hashing/hash-functions/#domain_and_range).
 #[derive(Copy, Clone, Eq, PartialEq, Default, Hash, Deserialize, Serialize, PartialOrd, Ord)]

src/hash_test.rs

@@ -1,4 +1,6 @@
-use crate::hash::{pedersen_hash, pedersen_hash_array, StarkFelt};
+use web3::types::U256;
+
+use crate::hash::{pedersen_hash, pedersen_hash_array, starknet_keccak, StarkFelt, MASK};
 use crate::stark_felt;
 
 #[test]
@@ -67,3 +69,20 @@ fn hash_serde() {
         assert_eq!(bytes, d.0);
     }
 }
+
+#[test]
+fn starknet_keccak_mask() {
+    let mask: U256 = U256::pow(U256::from(2), U256::from(250)) - U256::from(1);
+    assert_eq!(mask, MASK);
+}
+
+#[test]
+fn starknet_keccak_calculation() {
+    // Test result is taken from <https://www.cairo-lang.org/docs/hello_starknet/intro.html> tutorial.
+    // increase_balance function selector can be found in contract_compiled.json ->
+    // entry_points_by_type object.
+    let expected_keccak_felt =
+        stark_felt!("0x362398bec32bc0ebb411203221a35a0301193a96f317ebe5e40be9f60d15320");
+    let increase_balance_keccak_felt = starknet_keccak("increase_balance".as_bytes()).unwrap();
+    assert_eq!(increase_balance_keccak_felt, expected_keccak_felt);
+}