Arkworks MiMC

Arkworks implementation of cryptographic hash function MiMC [AGR+16] on $n/n$ non-feistel and $2n/n$ feistel block cipher with variable round keys and exponentiation.

R1CS gadgets and CRH gadget traits are available under r1cs crate feature.

Supported Field Parameters

We provide pre-generated round keys for some selected prime fields which available in circomlibjs package.

Feistel ($2n/n$)

• 220 rounds with $x^5$ on BN254
• 220 rounds with $x^5$ on BLS12-381
• 218 rounds with $x^5$ on BLS12-377

Non-Feistel ($n/n$)

• 91 rounds with $x^7$ on BN254
• 91 rounds with $x^7$ on BLS12-381
• 90 rounds with $x^7$ on BLS12-377

Usage

Custom Rounds And Exponent

```rust // Create new struct to use as MiMC param

[derive(Clone, Default)]

struct MyMiMCParams;

// Implement MiMCParameters for that struct impl MiMCParameters for MyMiMCParams { const ROUNDS: usize = 220; // Customizable const EXPONENT: usize = 3; // Customizable }

// Randomize MiMC key and round keys let mimc = as CRHTrait>::setup(rng)?; // Or initialize with customized key/round keys/outputs let custommimc = MiMC::new(1, Fr::from(1), mimc.roundkeys.clone());

// Use MiMC directly, // Non-Feistel let _ = mimc.permutenonfeistel(vec![Fr::from(1), Fr::from(0)]) // Feistel let _ = mimc.permute_feistel(vec![Fr::from(1), Fr::from(0)]);

// Or use MiMC through arkworks's crypto-primitive traits // CRH let _ = as CRH>::evaluate( &mimc, &tobytes!(Fr::from(1))? )?; // CRH let _ = as TwoToOneCRH>::evaluate( &mimc, &tobytes!(Fr::from(1))? )?; ```

Pre-Generated Rounds

Enable specific feature containing parameter that will be used.

In cargo.toml

toml arkworks-mimc = { ..., features = ["mimc-7-91-bn254"] }

In .rs

rust let mimc = MiMC::<Fr, MIMC_7_91_BN254_PARAMS>::new( 1, Fr::zero(), round_keys_contants_to_vec(&MIMC_7_91_BN254_ROUND_KEYS), );