X-Git-Url: http://www.git.cypherpunks.ru/?a=blobdiff_plain;f=gost28147%2Fcfb.go;fp=gost28147%2Fcfb.go;h=dfcd8f7b7f9812ea3f23c52a34580cf3f6a8d8f8;hb=c07494bbd559b9d00f391e28cfd070e18afe9900;hp=0000000000000000000000000000000000000000;hpb=107600dede989f0cc479b5a72c5f97e174307154;p=gogost.git

diff --git a/gost28147/cfb.go b/gost28147/cfb.go
new file mode 100644
index 0000000..dfcd8f7
--- /dev/null
+++ b/gost28147/cfb.go
@@ -0,0 +1,80 @@
+// GoGOST -- Pure Go GOST cryptographic functions library
+// Copyright (C) 2015-2019 Sergey Matveev <stargrave@stargrave.org>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, version 3 of the License.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package gost28147
+
+type CFBEncrypter struct {
+	c  *Cipher
+	iv []byte
+}
+
+func (c *Cipher) NewCFBEncrypter(iv []byte) *CFBEncrypter {
+	if len(iv) != BlockSize {
+		panic("iv length is not equal to blocksize")
+	}
+	encrypter := CFBEncrypter{c: c, iv: make([]byte, BlockSize)}
+	copy(encrypter.iv, iv)
+	return &encrypter
+}
+
+func (c *CFBEncrypter) XORKeyStream(dst, src []byte) {
+	var n int
+	i := 0
+MainLoop:
+	for {
+		c.c.Encrypt(c.iv, c.iv)
+		for n = 0; n < BlockSize; n++ {
+			if i*BlockSize+n == len(src) {
+				break MainLoop
+			}
+			c.iv[n] ^= src[i*BlockSize+n]
+			dst[i*BlockSize+n] = c.iv[n]
+		}
+		i++
+	}
+	return
+}
+
+type CFBDecrypter struct {
+	c  *Cipher
+	iv []byte
+}
+
+func (c *Cipher) NewCFBDecrypter(iv []byte) *CFBDecrypter {
+	if len(iv) != BlockSize {
+		panic("iv length is not equal to blocksize")
+	}
+	decrypter := CFBDecrypter{c: c, iv: make([]byte, BlockSize)}
+	copy(decrypter.iv, iv)
+	return &decrypter
+}
+
+func (c *CFBDecrypter) XORKeyStream(dst, src []byte) {
+	var n int
+	i := 0
+MainLoop:
+	for {
+		c.c.Encrypt(c.iv, c.iv)
+		for n = 0; n < BlockSize; n++ {
+			if i*BlockSize+n == len(src) {
+				break MainLoop
+			}
+			dst[i*BlockSize+n] = c.iv[n] ^ src[i*BlockSize+n]
+			c.iv[n] = src[i*BlockSize+n]
+		}
+		i++
+	}
+	return
+}