Add benchmark

On a Intel(R) Core(TM) i7-8705G CPU @ 3.10GHz, with 32 GB of RAM:
hash	time:   [927.61 us 927.78 us 927.98 us]

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mimc-rs"
-version = "0.0.2"
+version = "0.0.3"
 authors = ["arnaucube <root@arnaucube.com>"]
 edition = "2018"
 license = "GPL-3.0"
@@ -9,8 +9,18 @@ repository = "https://github.com/arnaucube/mimc-rs"
 readme = "README.md"
 
 [dependencies]
+ff = {package="ff_ce" , version="0.11", features = ["derive"]}
+rand = "0.4"
+
 num = "0.2.0"
 num-bigint = "0.2.2"
 num-traits = "0.2.8"
 tiny-keccak = "1.5"
 rustc-hex = "1.0.0"
+
+[dev-dependencies]
+criterion = "0.3"
+
+[[bench]]
+name = "bench_mimc_hash"
+harness = false

benches/bench_mimc_hash.rs

@@ -0,0 +1,27 @@
+use criterion::{criterion_group, criterion_main, Criterion};
+
+use num_bigint::BigInt;
+
+use mimc_rs::Mimc7;
+
+fn criterion_benchmark(c: &mut Criterion) {
+    let b1: BigInt = BigInt::parse_bytes(
+        b"12242166908188651009877250812424843524687801523336557272219921456462821518061",
+        10,
+    )
+    .unwrap();
+    let b2: BigInt = BigInt::parse_bytes(
+        b"12242166908188651009877250812424843524687801523336557272219921456462821518061",
+        10,
+    )
+    .unwrap();
+    let mut big_arr: Vec<BigInt> = Vec::new();
+    big_arr.push(b1.clone());
+    big_arr.push(b2.clone());
+    let mimc7 = Mimc7::new();
+
+    c.bench_function("hash", |b| b.iter(|| mimc7.hash(big_arr.clone()).unwrap()));
+}
+
+criterion_group!(benches, criterion_benchmark);
+criterion_main!(benches);