add frame size to poseidon hasher

babyjub/babyjub_wrapper_test.go

@@ -29,7 +29,8 @@ func TestBjjWrappedPrivateKeyInterfaceImpl(t *testing.T) {
 func TestBjjWrappedPrivateKey(t *testing.T) {
 	pk := RandomBjjWrappedKey()
 
-	hasher := poseidon.New()
+	hasher, err := poseidon.New(16)
+	require.NoError(t, err)
 	hasher.Write([]byte("test"))
 	digest := hasher.Sum(nil)
 

poseidon/poseidon_wrapper.go

@@ -2,25 +2,32 @@ package poseidon
 
 import (
 	"bytes"
+	"errors"
 	"hash"
 )
 
 type digest struct {
-	buf *bytes.Buffer
+	buf       *bytes.Buffer
+	frameSize int
 }
 
 // NewPoseidon returns the Poseidon hash of the input bytes.
+// use frame size of 16 inputs by default
 func NewPoseidon(b []byte) []byte {
-	h := New()
+	h, _ := New(16)
 	h.Write(b)
 	return h.Sum(nil)
 }
 
 // New returns a new hash.Hash computing the Poseidon hash.
-func New() hash.Hash {
-	return &digest{
-		buf: bytes.NewBuffer([]byte{}),
+func New(frameSize int) (hash.Hash, error) {
+	if frameSize < 2 || frameSize > 16 {
+		return nil, errors.New("incorrect frame size")
 	}
+	return &digest{
+		buf:       bytes.NewBuffer([]byte{}),
+		frameSize: frameSize,
+	}, nil
 }
 
 // Write (via the embedded io.Writer interface) adds more data to the running hash.
@@ -30,7 +37,7 @@ func (d *digest) Write(p []byte) (n int, err error) {
 
 // Sum returns the Poseidon checksum of the data.
 func (d *digest) Sum(b []byte) []byte {
-	hahs, err := HashBytes(d.buf.Bytes())
+	hahs, err := HashBytesX(d.buf.Bytes(), d.frameSize)
 	if err != nil {
 		panic(err)
 	}

poseidon/poseidon_wrapper_test.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"testing"
 
-	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
@@ -58,12 +57,13 @@ func TestPoseidonWrapperSum(t *testing.T) {
 			inputBytes, err := hex.DecodeString(vector.bytes)
 			require.NoError(t, err)
 
-			hasher := New()
+			hasher, err := New(16)
+			require.NoError(t, err)
 			hasher.Write(inputBytes)
 			res := hasher.Sum(nil)
 
 			require.NotEmpty(t, res)
-			assert.Equal(t, vector.expectedHash, hex.EncodeToString(res))
+			require.Equal(t, vector.expectedHash, hex.EncodeToString(res))
 		})
 	}
 }
@@ -120,7 +120,7 @@ func TestPoseidonNewPoseidon(t *testing.T) {
 			res := NewPoseidon(inputBytes)
 
 			require.NotEmpty(t, res)
-			assert.Equal(t, vector.expectedHash, hex.EncodeToString(res))
+			require.Equal(t, vector.expectedHash, hex.EncodeToString(res))
 		})
 	}
 }