diff --git a/README.md b/README.md
index 8ffcb77..15f9030 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,6 @@
 # keccak256-circom [![Test](https://github.com/arnaucube/keccak256-circom/workflows/Test/badge.svg)](https://github.com/arnaucube/keccak256-circom/actions?query=workflow%3ATest)
 
-WIP repo. Once ready, will do a PR into [circomlib](https://github.com/iden3/circomlib).
+Keccak256 hash function (ethereum version) implemented in [circom](https://github.com/iden3/circom). Spec: https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.202.pdf
+
+**Warning**: WIP, this is an experimental repo.
 
-Spec: https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.202.pdf
diff --git a/circuits/keccak256.circom b/circuits/keccak256.circom
new file mode 100644
index 0000000..a646742
--- /dev/null
+++ b/circuits/keccak256.circom
@@ -0,0 +1,46 @@
+pragma circom 2.0.0;
+
+include "./utils.circom";
+
+template Pad(nBits) {
+    signal input in[nBits];
+    var blockSize=136*8;
+    signal output out[blockSize];
+    signal out2[blockSize];
+    var i;
+
+    for (i=0; i<nBits; i++) {
+        out2[i] <== in[i];
+    }
+    var domain = 0x01;
+    for (i=0; i<8; i++) {
+        out2[nBits+i] <== (domain >> i) & 1;
+    }
+    for (i=nBits+8; i<blockSize; i++) {
+        out2[i] <== 0;
+    }
+    component aux = OrArray(8);
+    for (i=0; i<8; i++) {
+        aux.a[i] <== out2[blockSize-8+i];
+        aux.b[i] <== (0x80 >> i) & 1;
+    }
+    for (i=0; i<8; i++) {
+        out[blockSize-8+i] <== aux.out[i];
+    }
+    for (i=0; i<blockSize-8; i++) {
+        out[i]<==out2[i];
+    }
+}
+
+template Keccak256(nBits) {
+    signal input in[nBits];
+    signal output out[256];
+    var i;
+
+    // pad
+    component pad = Pad(nBits);
+    for (i=0; i<nBits; i++) {
+        pad.in[i] <== in[i];
+    }
+    
+}
diff --git a/go-keccak256-bits-impl/keccak_test.go b/go-keccak256-bits-impl/keccak_test.go
index aeb21ec..49b77e8 100644
--- a/go-keccak256-bits-impl/keccak_test.go
+++ b/go-keccak256-bits-impl/keccak_test.go
@@ -2,6 +2,7 @@ package keccak
 
 import (
 	"encoding/hex"
+	"fmt"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/crypto"
@@ -23,3 +24,29 @@ func testKeccak(t *testing.T, input []byte, expectedHex string) {
 	qt.Assert(t, h, qt.DeepEquals, expected)
 	qt.Assert(t, hex.EncodeToString(h), qt.Equals, expectedHex)
 }
+
+func TestPad(t *testing.T) {
+	b := make([]byte, 32)
+	for i := 0; i < len(b); i++ {
+		b[i] = byte(i)
+	}
+	fmt.Println(b)
+	bBits := bytesToBits(b)
+	fBits := pad(bBits)
+
+	qt.Assert(t, bitsToBytes(fBits[:]), qt.DeepEquals,
+		[]byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 128})
+}
+
+func TestFinal(t *testing.T) {
+	b := make([]byte, 32)
+	for i := 0; i < len(b); i++ {
+		b[i] = byte(i)
+	}
+	fmt.Println(b)
+	bBits := bytesToBits(b)
+	fBits := final(bBits)
+
+	qt.Assert(t, bitsToU64Array(fBits[:]), qt.DeepEquals,
+		[]uint64{16953415415620100490, 7495738965189503699, 12723370805759944158, 3295955328722933810, 12121371508560456016, 174876831679863147, 15944933357501475584, 7502339663607726274, 12048918224562833898, 16715284461100269102, 15582559130083209842, 1743886467337678829, 2424196198791253761, 1116417308245482383, 10367365997906434042, 1849801549382613906, 13294939539683415102, 4478091053375708790, 2969967870313332958, 14618962068930014237, 2721742233407503451, 12003265593030191290, 8109318293656735684, 6346795302983965746, 12210038122000333046})
+}
diff --git a/test/circuits/pad_test.circom b/test/circuits/pad_test.circom
new file mode 100644
index 0000000..25d1644
--- /dev/null
+++ b/test/circuits/pad_test.circom
@@ -0,0 +1,5 @@
+pragma circom 2.0.0;
+
+include "../../circuits/keccak256.circom";
+
+component main = Pad(32*8);
diff --git a/test/keccak256.js b/test/keccak256.js
index dfcb9c4..d01eb9f 100644
--- a/test/keccak256.js
+++ b/test/keccak256.js
@@ -218,3 +218,24 @@ describe("Iota test", function () {
 	assert.deepEqual(stateOutU64, expectedOut);
     });
 });
+
+describe("Keccak-Pad test", function () {
+    this.timeout(100000);
+
+    it ("Pad (testvector generated from go)", async () => {
+	const cir = await wasm_tester(path.join(__dirname, "circuits", "pad_test.circom"));
+
+	const input = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31];
+	const expectedOut = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 128];
+
+	const stateIn = bytesToBits(input);
+
+	const witness = await cir.calculateWitness({ "in": stateIn }, true);
+
+	const stateOut = witness.slice(1, 1+(136*8));
+	const stateOutBytes = bitsToBytes(stateOut);
+	// console.log(stateOutBytes, expectedOut);
+	assert.deepEqual(stateOutBytes, expectedOut);
+    });
+});
+