From d82699bf438fe3c991f47df08ec07d8283f86b2a Mon Sep 17 00:00:00 2001
From: Ethan Buchman <ethan@coinculture.info>
Date: Mon, 21 May 2018 20:15:32 -0400
Subject: [PATCH] tmhash

---
 merkle/simple_map.go       |  4 ++--
 merkle/simple_tree.go      |  6 +++---
 merkle/tmhash/hash.go      | 41 ++++++++++++++++++++++++++++++++++++++
 merkle/tmhash/hash_test.go | 23 +++++++++++++++++++++
 4 files changed, 69 insertions(+), 5 deletions(-)
 create mode 100644 merkle/tmhash/hash.go
 create mode 100644 merkle/tmhash/hash_test.go

diff --git a/merkle/simple_map.go b/merkle/simple_map.go
index cd38de761..bd5c88d85 100644
--- a/merkle/simple_map.go
+++ b/merkle/simple_map.go
@@ -2,7 +2,7 @@ package merkle
 
 import (
 	cmn "github.com/tendermint/tmlibs/common"
-	"golang.org/x/crypto/ripemd160"
+	"github.com/tendermint/tmlibs/merkle/tmhash"
 )
 
 type SimpleMap struct {
@@ -63,7 +63,7 @@ func (sm *SimpleMap) KVPairs() cmn.KVPairs {
 type KVPair cmn.KVPair
 
 func (kv KVPair) Hash() []byte {
-	hasher := ripemd160.New()
+	hasher := tmhash.New()
 	err := encodeByteSlice(hasher, kv.Key)
 	if err != nil {
 		panic(err)
diff --git a/merkle/simple_tree.go b/merkle/simple_tree.go
index 9bdf52cb2..6bd80f55f 100644
--- a/merkle/simple_tree.go
+++ b/merkle/simple_tree.go
@@ -25,11 +25,11 @@ For larger datasets, use IAVLTree.
 package merkle
 
 import (
-	"golang.org/x/crypto/ripemd160"
+	"github.com/tendermint/tmlibs/merkle/tmhash"
 )
 
 func SimpleHashFromTwoHashes(left []byte, right []byte) []byte {
-	var hasher = ripemd160.New()
+	var hasher = tmhash.New()
 	err := encodeByteSlice(hasher, left)
 	if err != nil {
 		panic(err)
@@ -68,7 +68,7 @@ func SimpleHashFromByteslices(bzs [][]byte) []byte {
 }
 
 func SimpleHashFromBytes(bz []byte) []byte {
-	hasher := ripemd160.New()
+	hasher := tmhash.New()
 	hasher.Write(bz)
 	return hasher.Sum(nil)
 }
diff --git a/merkle/tmhash/hash.go b/merkle/tmhash/hash.go
new file mode 100644
index 000000000..de69c406f
--- /dev/null
+++ b/merkle/tmhash/hash.go
@@ -0,0 +1,41 @@
+package tmhash
+
+import (
+	"crypto/sha256"
+	"hash"
+)
+
+var (
+	Size      = 20
+	BlockSize = sha256.BlockSize
+)
+
+type sha256trunc struct {
+	sha256 hash.Hash
+}
+
+func (h sha256trunc) Write(p []byte) (n int, err error) {
+	return h.sha256.Write(p)
+}
+func (h sha256trunc) Sum(b []byte) []byte {
+	shasum := h.sha256.Sum(b)
+	return shasum[:Size]
+}
+
+func (h sha256trunc) Reset() {
+	h.sha256.Reset()
+}
+
+func (h sha256trunc) Size() int {
+	return Size
+}
+
+func (h sha256trunc) BlockSize() int {
+	return h.sha256.BlockSize()
+}
+
+func New() hash.Hash {
+	return sha256trunc{
+		sha256: sha256.New(),
+	}
+}
diff --git a/merkle/tmhash/hash_test.go b/merkle/tmhash/hash_test.go
new file mode 100644
index 000000000..c9e80f2bc
--- /dev/null
+++ b/merkle/tmhash/hash_test.go
@@ -0,0 +1,23 @@
+package tmhash_test
+
+import (
+	"crypto/sha256"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/tendermint/tmlibs/merkle/tmhash"
+)
+
+func TestHash(t *testing.T) {
+	testVector := []byte("abc")
+	hasher := tmhash.New()
+	hasher.Write(testVector)
+	bz := hasher.Sum(nil)
+
+	hasher = sha256.New()
+	hasher.Write(testVector)
+	bz2 := hasher.Sum(nil)
+	bz2 = bz2[:20]
+
+	assert.Equal(t, bz, bz2)
+}