1 files changed, 60 insertions, 0 deletions
diff --git a/crypto/sha3/shake.go b/crypto/sha3/shake.go
new file mode 100644
index 000000000..841f9860f
--- /dev/null
+++ b/crypto/sha3/shake.go
@@ -0,0 +1,60 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sha3
+
+// This file defines the ShakeHash interface, and provides
+// functions for creating SHAKE instances, as well as utility
+// functions for hashing bytes to arbitrary-length output.
+
+import (
+	"io"
+)
+
+// ShakeHash defines the interface to hash functions that
+// support arbitrary-length output.
+type ShakeHash interface {
+	// Write absorbs more data into the hash's state. It panics if input is
+	// written to it after output has been read from it.
+	io.Writer
+
+	// Read reads more output from the hash; reading affects the hash's
+	// state. (ShakeHash.Read is thus very different from Hash.Sum)
+	// It never returns an error.
+	io.Reader
+
+	// Clone returns a copy of the ShakeHash in its current state.
+	Clone() ShakeHash
+
+	// Reset resets the ShakeHash to its initial state.
+	Reset()
+}
+
+func (d *state) Clone() ShakeHash {
+	return d.clone()
+}
+
+// NewShake128 creates a new SHAKE128 variable-output-length ShakeHash.
+// Its generic security strength is 128 bits against all attacks if at
+// least 32 bytes of its output are used.
+func NewShake128() ShakeHash { return &state{rate: 168, dsbyte: 0x1f} }
+
+// NewShake256 creates a new SHAKE128 variable-output-length ShakeHash.
+// Its generic security strength is 256 bits against all attacks if
+// at least 64 bytes of its output are used.
+func NewShake256() ShakeHash { return &state{rate: 136, dsbyte: 0x1f} }
+
+// ShakeSum128 writes an arbitrary-length digest of data into hash.
+func ShakeSum128(hash, data []byte) {
+	h := NewShake128()
+	h.Write(data)
+	h.Read(hash)
+}
+
+// ShakeSum256 writes an arbitrary-length digest of data into hash.
+func ShakeSum256(hash, data []byte) {
+	h := NewShake256()
+	h.Write(data)
+	h.Read(hash)
+}