--- /dev/null
+// 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
+}