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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
commit554fd8c5195424bdbcabf5de30fdc183aba391bd (patch)
tree976dc5ab7fddf506dadce60ae936f43f58787092 /libgo/go/crypto/cipher/ofb.go
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Diffstat (limited to 'libgo/go/crypto/cipher/ofb.go')
-rw-r--r--libgo/go/crypto/cipher/ofb.go44
1 files changed, 44 insertions, 0 deletions
diff --git a/libgo/go/crypto/cipher/ofb.go b/libgo/go/crypto/cipher/ofb.go
new file mode 100644
index 000000000..85e5f02b0
--- /dev/null
+++ b/libgo/go/crypto/cipher/ofb.go
@@ -0,0 +1,44 @@
+// Copyright 2011 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.
+
+// OFB (Output Feedback) Mode.
+
+package cipher
+
+type ofb struct {
+ b Block
+ out []byte
+ outUsed int
+}
+
+// NewOFB returns a Stream that encrypts or decrypts using the block cipher b
+// in output feedback mode. The initialization vector iv's length must be equal
+// to b's block size.
+func NewOFB(b Block, iv []byte) Stream {
+ blockSize := b.BlockSize()
+ if len(iv) != blockSize {
+ return nil
+ }
+
+ x := &ofb{
+ b: b,
+ out: make([]byte, blockSize),
+ outUsed: 0,
+ }
+ b.Encrypt(x.out, iv)
+
+ return x
+}
+
+func (x *ofb) XORKeyStream(dst, src []byte) {
+ for i, s := range src {
+ if x.outUsed == len(x.out) {
+ x.b.Encrypt(x.out, x.out)
+ x.outUsed = 0
+ }
+
+ dst[i] = s ^ x.out[x.outUsed]
+ x.outUsed++
+ }
+}