Add Hash160 func to calculate ripemd160(sha256(data)).

hash160.go

@@ -0,0 +1,22 @@
+// Copyright (c) 2013 Conformal Systems LLC.
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package btcutil
+
+import (
+	"code.google.com/p/go.crypto/ripemd160"
+	"crypto/sha256"
+	"hash"
+)
+
+// Calculate the hash of hasher over buf.
+func calcHash(buf []byte, hasher hash.Hash) []byte {
+	hasher.Write(buf)
+	return hasher.Sum(nil)
+}
+
+// Hash160 calculates the hash ripemd160(sha256(b)).
+func Hash160(buf []byte) []byte {
+	return calcHash(calcHash(buf, sha256.New()), ripemd160.New())
+}