Fix @ismail comments

crypto/hashers/coniks/coniks.go

@@ -0,0 +1,80 @@
+// TODO(huyvq): Remove package import.
+// Other package shouldn't need to import this package,
+// instead they should insert `hashers` and import this
+// package using a blank import name.
+// Should be adressed in #06.
+
+package coniks
+
+import (
+	"crypto"
+
+	"github.com/coniks-sys/coniks-go/crypto/hashers"
+	"github.com/coniks-sys/coniks-go/utils"
+)
+
+func init() {
+	hashers.RegisterHasher(CONIKS_Hash_SHA512_256, New)
+}
+
+const (
+	// CONIKS_Hash_SHA512_256 is the identity of the hashing strategy
+	// specified in the Coniks paper with SHA512_256 as the hash algorithm.
+	CONIKS_Hash_SHA512_256 = "CONIKS_Hash_SHA512_256"
+
+	emptyIdentifier = 'E'
+	leafIdentifier  = 'L'
+)
+
+type hasher struct {
+	crypto.Hash
+}
+
+// New returns an instance of CONIKS_Hash_SHA512_256.
+func New() hashers.PADHasher {
+	return &hasher{Hash: crypto.SHA512_256}
+}
+
+func (ch *hasher) Digest(ms ...[]byte) []byte {
+	h := ch.New()
+	for _, m := range ms {
+		h.Write(m)
+	}
+	return h.Sum(nil)
+}
+
+func (hasher) ID() string {
+	return CONIKS_Hash_SHA512_256
+}
+
+func (ch *hasher) Size() int {
+	return ch.Size()
+}
+
+// HashInterior computes the hash of an interior node as: H(left || right).
+func (ch *hasher) HashInterior(left, right []byte) []byte {
+	return ch.Digest(left, right)
+}
+
+// HashLeaf computes the hash of a user leaf node as:
+// H(Identifier || nonce || index || level || commit).
+func (ch *hasher) HashLeaf(nonce []byte, index []byte, level uint32, commit []byte) []byte {
+	return ch.Digest(
+		[]byte{leafIdentifier},
+		nonce,
+		index,
+		utils.UInt32ToBytes(level),
+		commit,
+	)
+}
+
+// HashEmpty computes the hash of an empty leaf node as:
+// H(Identifier || nonce || index || level).
+func (ch *hasher) HashEmpty(nonce []byte, index []byte, level uint32) []byte {
+	return ch.Digest(
+		[]byte{emptyIdentifier},
+		nonce,
+		index,
+		utils.UInt32ToBytes(level),
+	)
+}

crypto/hasher/coniks/coniks_test.go → crypto/hashers/coniks/coniks_test.go

@@ -4,23 +4,23 @@ import (
 	"encoding/hex"
 	"testing"
 
-	"github.com/coniks-sys/coniks-go/crypto/hasher"
+	"github.com/coniks-sys/coniks-go/crypto/hashers"
 )
 
 // h2h converts a hex string into its Hash object.
-func h2h(h string) hasher.Hash {
+func h2h(h string) hashers.Hash {
 	b, err := hex.DecodeString(h)
 	if err != nil {
 		panic("invalid hex string")
 	}
-	var ret hasher.Hash
+	var ret hashers.Hash
 	copy(ret[:], b)
 	return ret
 }
 
 // s2h converts a byte slice into its Hash object.
-func s2h(s []byte) hasher.Hash {
-	var ret hasher.Hash
+func s2h(s []byte) hashers.Hash {
+	var ret hashers.Hash
 	copy(ret[:], s)
 	return ret
 }
@@ -31,7 +31,7 @@ func TestHashLeafVectors(t *testing.T) {
 		index     []byte
 		depth     uint32
 		leaf      []byte
-		want      hasher.Hash
+		want      hashers.Hash
 	}{
 		{treeNonce: [32]byte{0}, index: []byte("foo"), depth: 128, leaf: []byte("leaf"), want: h2h("65e7f29787a6168affd016656bb1f4f03af91cf7416270f5015005f8594d3eb6")},
 	} {
@@ -46,7 +46,7 @@ func TestHashEmptyVectors(t *testing.T) {
 		treeNonce [32]byte // treeNonce is treeID in KT, it should be a 32-byte array for cross-project compatibility
 		index     []byte
 		depth     uint32
-		want      hasher.Hash
+		want      hashers.Hash
 	}{
 		{treeNonce: [32]byte{0}, index: []byte("foo"), depth: 128, want: h2h("1a6b0eb739b32a46e7d679a9be03f522e907f53423aacb82e550bf657d1afb10")},
 	} {

crypto/hasher/hasher.go → crypto/hashers/hasher.go

@@ -1,4 +1,4 @@
-package hasher
+package hashers
 
 import (
 	"fmt"
@@ -9,28 +9,24 @@ import (
 // Hash represents the output of the used hash function.
 type Hash [crypto.DefaultHashSizeByte]byte
 
-// PADHasher provides hash functions for the PAD implementations.
+// PADHasher provides hash functions for the PAD implementations,
+// and defines the way empty / node / leaf hashes of the underlying tree
+// are constructed.
 type PADHasher interface {
 	// ID returns the name of the cryptographic hash function.
 	ID() string
 	// Size returns the size of the hash output in bytes.
 	Size() int
 	// Digest hashes all passed byte slices. The passed slices won't be mutated.
 	Digest(ms ...[]byte) []byte
-	treeHasher
-}
 
-// treeHasher provides hash functions for tree implementations.
-type treeHasher interface {
-	// HashInterior computes the hash of an interior node as: H(left || right)
+	// HashInterior computes the hash of an interior node.
 	HashInterior(left, right []byte) []byte
 
-	// HashLeaf computes the hash of a user leaf node as:
-	// H(Identifier || nonce || index || level || commit)
+	// HashLeaf computes the hash of a user leaf node.
 	HashLeaf(nonce []byte, index []byte, level uint32, data []byte) []byte
 
-	// HashEmpty computes the hash of an empty leaf node as:
-	// H(Identifier || nonce || index || level)
+	// HashEmpty computes the hash of an empty leaf node.
 	HashEmpty(nonce []byte, index []byte, level uint32) []byte
 }
 
@@ -44,8 +40,9 @@ func RegisterHasher(h string, f func() PADHasher) {
 	hashers[h] = f()
 }
 
-// Hasher returns a PADHasher.
-func Hasher(h string) (PADHasher, error) {
+// NewPADHasher returns a registered PADHasher identified by the given string.
+// If no such PADHasher exists, it returns an error.
+func NewPADHasher(h string) (PADHasher, error) {
 	if f, ok := hashers[h]; ok {
 		return f, nil
 	}

crypto/hasher/hasher_test.go → crypto/hashers/hasher_test.go

@@ -1,4 +1,4 @@
-package hasher
+package hashers
 
 import (
 	"testing"
@@ -25,7 +25,7 @@ func TestGetHasher(t *testing.T) {
 		RegisterHasher(fakeHasherID, fakeHasher)
 	}
 
-	_, err := Hasher(fakeHasherID)
+	_, err := NewPADHasher(fakeHasherID)
 	if err != nil {
 		t.Error("Expect a hasher.")
 	}

merkletree/merkletree.go

@@ -5,7 +5,7 @@ import (
 	"errors"
 
 	"github.com/coniks-sys/coniks-go/crypto"
-	"github.com/coniks-sys/coniks-go/crypto/hasher"
+	"github.com/coniks-sys/coniks-go/crypto/hashers"
 	"github.com/coniks-sys/coniks-go/utils"
 )
 
@@ -63,7 +63,7 @@ func (m *MerkleTree) Get(lookupIndex []byte) *AuthenticationPath {
 			break
 		}
 		direction := lookupIndexBits[depth]
-		var hashArr hasher.Hash
+		var hashArr hashers.Hash
 		if direction {
 			copy(hashArr[:], nodePointer.(*interiorNode).leftHash)
 			nodePointer = nodePointer.(*interiorNode).rightChild

merkletree/node.go

@@ -2,7 +2,7 @@ package merkletree
 
 import (
 	"github.com/coniks-sys/coniks-go/crypto"
-	chasher "github.com/coniks-sys/coniks-go/crypto/hasher/coniks"
+	chasher "github.com/coniks-sys/coniks-go/crypto/hashers/coniks"
 	"github.com/coniks-sys/coniks-go/utils"
 )
 

merkletree/pad.go

@@ -5,7 +5,7 @@ import (
 	"errors"
 
 	"github.com/coniks-sys/coniks-go/crypto"
-	chasher "github.com/coniks-sys/coniks-go/crypto/hasher/coniks"
+	chasher "github.com/coniks-sys/coniks-go/crypto/hashers/coniks"
 	"github.com/coniks-sys/coniks-go/crypto/sign"
 	"github.com/coniks-sys/coniks-go/crypto/vrf"
 )

merkletree/proof.go

@@ -5,8 +5,8 @@ import (
 	"errors"
 
 	"github.com/coniks-sys/coniks-go/crypto"
-	"github.com/coniks-sys/coniks-go/crypto/hasher"
-	chasher "github.com/coniks-sys/coniks-go/crypto/hasher/coniks"
+	"github.com/coniks-sys/coniks-go/crypto/hashers"
+	chasher "github.com/coniks-sys/coniks-go/crypto/hashers/coniks"
 	"github.com/coniks-sys/coniks-go/utils"
 )
 
@@ -74,7 +74,7 @@ const (
 // equals the lookup index.
 type AuthenticationPath struct {
 	TreeNonce   []byte
-	PrunedTree  []hasher.Hash
+	PrunedTree  []hashers.Hash
 	LookupIndex []byte
 	VrfProof    []byte
 	Leaf        *ProofNode

merkletree/str.go

@@ -3,7 +3,7 @@ package merkletree
 import (
 	"bytes"
 
-	chasher "github.com/coniks-sys/coniks-go/crypto/hasher/coniks"
+	chasher "github.com/coniks-sys/coniks-go/crypto/hashers/coniks"
 	"github.com/coniks-sys/coniks-go/crypto/sign"
 	"github.com/coniks-sys/coniks-go/utils"
 )

protocol/policy.go

@@ -1,7 +1,7 @@
 package protocol
 
 import (
-	chasher "github.com/coniks-sys/coniks-go/crypto/hasher/coniks"
+	chasher "github.com/coniks-sys/coniks-go/crypto/hashers/coniks"
 	"github.com/coniks-sys/coniks-go/crypto/vrf"
 	"github.com/coniks-sys/coniks-go/merkletree"
 	"github.com/coniks-sys/coniks-go/utils"