rc2.go raw
1 // Copyright 2015 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4
5 // Package rc2 implements the RC2 cipher
6 /*
7 https://www.ietf.org/rfc/rfc2268.txt
8 http://people.csail.mit.edu/rivest/pubs/KRRR98.pdf
9
10 This code is licensed under the MIT license.
11 */
12 package rc2
13
14 import (
15 "crypto/cipher"
16 "encoding/binary"
17 "math/bits"
18 )
19
20 // The rc2 block size in bytes
21 const BlockSize = 8
22
23 type rc2Cipher struct {
24 k [64]uint16
25 }
26
27 // New returns a new rc2 cipher with the given key and effective key length t1
28 func New(key []byte, t1 int) (cipher.Block, error) {
29 // TODO(dgryski): error checking for key length
30 return &rc2Cipher{
31 k: expandKey(key, t1),
32 }, nil
33 }
34
35 func (*rc2Cipher) BlockSize() int { return BlockSize }
36
37 var piTable = [256]byte{
38 0xd9, 0x78, 0xf9, 0xc4, 0x19, 0xdd, 0xb5, 0xed, 0x28, 0xe9, 0xfd, 0x79, 0x4a, 0xa0, 0xd8, 0x9d,
39 0xc6, 0x7e, 0x37, 0x83, 0x2b, 0x76, 0x53, 0x8e, 0x62, 0x4c, 0x64, 0x88, 0x44, 0x8b, 0xfb, 0xa2,
40 0x17, 0x9a, 0x59, 0xf5, 0x87, 0xb3, 0x4f, 0x13, 0x61, 0x45, 0x6d, 0x8d, 0x09, 0x81, 0x7d, 0x32,
41 0xbd, 0x8f, 0x40, 0xeb, 0x86, 0xb7, 0x7b, 0x0b, 0xf0, 0x95, 0x21, 0x22, 0x5c, 0x6b, 0x4e, 0x82,
42 0x54, 0xd6, 0x65, 0x93, 0xce, 0x60, 0xb2, 0x1c, 0x73, 0x56, 0xc0, 0x14, 0xa7, 0x8c, 0xf1, 0xdc,
43 0x12, 0x75, 0xca, 0x1f, 0x3b, 0xbe, 0xe4, 0xd1, 0x42, 0x3d, 0xd4, 0x30, 0xa3, 0x3c, 0xb6, 0x26,
44 0x6f, 0xbf, 0x0e, 0xda, 0x46, 0x69, 0x07, 0x57, 0x27, 0xf2, 0x1d, 0x9b, 0xbc, 0x94, 0x43, 0x03,
45 0xf8, 0x11, 0xc7, 0xf6, 0x90, 0xef, 0x3e, 0xe7, 0x06, 0xc3, 0xd5, 0x2f, 0xc8, 0x66, 0x1e, 0xd7,
46 0x08, 0xe8, 0xea, 0xde, 0x80, 0x52, 0xee, 0xf7, 0x84, 0xaa, 0x72, 0xac, 0x35, 0x4d, 0x6a, 0x2a,
47 0x96, 0x1a, 0xd2, 0x71, 0x5a, 0x15, 0x49, 0x74, 0x4b, 0x9f, 0xd0, 0x5e, 0x04, 0x18, 0xa4, 0xec,
48 0xc2, 0xe0, 0x41, 0x6e, 0x0f, 0x51, 0xcb, 0xcc, 0x24, 0x91, 0xaf, 0x50, 0xa1, 0xf4, 0x70, 0x39,
49 0x99, 0x7c, 0x3a, 0x85, 0x23, 0xb8, 0xb4, 0x7a, 0xfc, 0x02, 0x36, 0x5b, 0x25, 0x55, 0x97, 0x31,
50 0x2d, 0x5d, 0xfa, 0x98, 0xe3, 0x8a, 0x92, 0xae, 0x05, 0xdf, 0x29, 0x10, 0x67, 0x6c, 0xba, 0xc9,
51 0xd3, 0x00, 0xe6, 0xcf, 0xe1, 0x9e, 0xa8, 0x2c, 0x63, 0x16, 0x01, 0x3f, 0x58, 0xe2, 0x89, 0xa9,
52 0x0d, 0x38, 0x34, 0x1b, 0xab, 0x33, 0xff, 0xb0, 0xbb, 0x48, 0x0c, 0x5f, 0xb9, 0xb1, 0xcd, 0x2e,
53 0xc5, 0xf3, 0xdb, 0x47, 0xe5, 0xa5, 0x9c, 0x77, 0x0a, 0xa6, 0x20, 0x68, 0xfe, 0x7f, 0xc1, 0xad,
54 }
55
56 func expandKey(key []byte, t1 int) [64]uint16 {
57
58 l := make([]byte, 128)
59 copy(l, key)
60
61 var t = len(key)
62 var t8 = (t1 + 7) / 8
63 var tm = byte(255 % uint(1<<(8+uint(t1)-8*uint(t8))))
64
65 for i := len(key); i < 128; i++ {
66 l[i] = piTable[l[i-1]+l[uint8(i-t)]]
67 }
68
69 l[128-t8] = piTable[l[128-t8]&tm]
70
71 for i := 127 - t8; i >= 0; i-- {
72 l[i] = piTable[l[i+1]^l[i+t8]]
73 }
74
75 var k [64]uint16
76
77 for i := range k {
78 k[i] = uint16(l[2*i]) + uint16(l[2*i+1])*256
79 }
80
81 return k
82 }
83
84 func (c *rc2Cipher) Encrypt(dst, src []byte) {
85
86 r0 := binary.LittleEndian.Uint16(src[0:])
87 r1 := binary.LittleEndian.Uint16(src[2:])
88 r2 := binary.LittleEndian.Uint16(src[4:])
89 r3 := binary.LittleEndian.Uint16(src[6:])
90
91 var j int
92
93 for j <= 16 {
94 // mix r0
95 r0 = r0 + c.k[j] + (r3 & r2) + ((^r3) & r1)
96 r0 = bits.RotateLeft16(r0, 1)
97 j++
98
99 // mix r1
100 r1 = r1 + c.k[j] + (r0 & r3) + ((^r0) & r2)
101 r1 = bits.RotateLeft16(r1, 2)
102 j++
103
104 // mix r2
105 r2 = r2 + c.k[j] + (r1 & r0) + ((^r1) & r3)
106 r2 = bits.RotateLeft16(r2, 3)
107 j++
108
109 // mix r3
110 r3 = r3 + c.k[j] + (r2 & r1) + ((^r2) & r0)
111 r3 = bits.RotateLeft16(r3, 5)
112 j++
113
114 }
115
116 r0 = r0 + c.k[r3&63]
117 r1 = r1 + c.k[r0&63]
118 r2 = r2 + c.k[r1&63]
119 r3 = r3 + c.k[r2&63]
120
121 for j <= 40 {
122 // mix r0
123 r0 = r0 + c.k[j] + (r3 & r2) + ((^r3) & r1)
124 r0 = bits.RotateLeft16(r0, 1)
125 j++
126
127 // mix r1
128 r1 = r1 + c.k[j] + (r0 & r3) + ((^r0) & r2)
129 r1 = bits.RotateLeft16(r1, 2)
130 j++
131
132 // mix r2
133 r2 = r2 + c.k[j] + (r1 & r0) + ((^r1) & r3)
134 r2 = bits.RotateLeft16(r2, 3)
135 j++
136
137 // mix r3
138 r3 = r3 + c.k[j] + (r2 & r1) + ((^r2) & r0)
139 r3 = bits.RotateLeft16(r3, 5)
140 j++
141
142 }
143
144 r0 = r0 + c.k[r3&63]
145 r1 = r1 + c.k[r0&63]
146 r2 = r2 + c.k[r1&63]
147 r3 = r3 + c.k[r2&63]
148
149 for j <= 60 {
150 // mix r0
151 r0 = r0 + c.k[j] + (r3 & r2) + ((^r3) & r1)
152 r0 = bits.RotateLeft16(r0, 1)
153 j++
154
155 // mix r1
156 r1 = r1 + c.k[j] + (r0 & r3) + ((^r0) & r2)
157 r1 = bits.RotateLeft16(r1, 2)
158 j++
159
160 // mix r2
161 r2 = r2 + c.k[j] + (r1 & r0) + ((^r1) & r3)
162 r2 = bits.RotateLeft16(r2, 3)
163 j++
164
165 // mix r3
166 r3 = r3 + c.k[j] + (r2 & r1) + ((^r2) & r0)
167 r3 = bits.RotateLeft16(r3, 5)
168 j++
169 }
170
171 binary.LittleEndian.PutUint16(dst[0:], r0)
172 binary.LittleEndian.PutUint16(dst[2:], r1)
173 binary.LittleEndian.PutUint16(dst[4:], r2)
174 binary.LittleEndian.PutUint16(dst[6:], r3)
175 }
176
177 func (c *rc2Cipher) Decrypt(dst, src []byte) {
178
179 r0 := binary.LittleEndian.Uint16(src[0:])
180 r1 := binary.LittleEndian.Uint16(src[2:])
181 r2 := binary.LittleEndian.Uint16(src[4:])
182 r3 := binary.LittleEndian.Uint16(src[6:])
183
184 j := 63
185
186 for j >= 44 {
187 // unmix r3
188 r3 = bits.RotateLeft16(r3, 16-5)
189 r3 = r3 - c.k[j] - (r2 & r1) - ((^r2) & r0)
190 j--
191
192 // unmix r2
193 r2 = bits.RotateLeft16(r2, 16-3)
194 r2 = r2 - c.k[j] - (r1 & r0) - ((^r1) & r3)
195 j--
196
197 // unmix r1
198 r1 = bits.RotateLeft16(r1, 16-2)
199 r1 = r1 - c.k[j] - (r0 & r3) - ((^r0) & r2)
200 j--
201
202 // unmix r0
203 r0 = bits.RotateLeft16(r0, 16-1)
204 r0 = r0 - c.k[j] - (r3 & r2) - ((^r3) & r1)
205 j--
206 }
207
208 r3 = r3 - c.k[r2&63]
209 r2 = r2 - c.k[r1&63]
210 r1 = r1 - c.k[r0&63]
211 r0 = r0 - c.k[r3&63]
212
213 for j >= 20 {
214 // unmix r3
215 r3 = bits.RotateLeft16(r3, 16-5)
216 r3 = r3 - c.k[j] - (r2 & r1) - ((^r2) & r0)
217 j--
218
219 // unmix r2
220 r2 = bits.RotateLeft16(r2, 16-3)
221 r2 = r2 - c.k[j] - (r1 & r0) - ((^r1) & r3)
222 j--
223
224 // unmix r1
225 r1 = bits.RotateLeft16(r1, 16-2)
226 r1 = r1 - c.k[j] - (r0 & r3) - ((^r0) & r2)
227 j--
228
229 // unmix r0
230 r0 = bits.RotateLeft16(r0, 16-1)
231 r0 = r0 - c.k[j] - (r3 & r2) - ((^r3) & r1)
232 j--
233
234 }
235
236 r3 = r3 - c.k[r2&63]
237 r2 = r2 - c.k[r1&63]
238 r1 = r1 - c.k[r0&63]
239 r0 = r0 - c.k[r3&63]
240
241 for j >= 0 {
242 // unmix r3
243 r3 = bits.RotateLeft16(r3, 16-5)
244 r3 = r3 - c.k[j] - (r2 & r1) - ((^r2) & r0)
245 j--
246
247 // unmix r2
248 r2 = bits.RotateLeft16(r2, 16-3)
249 r2 = r2 - c.k[j] - (r1 & r0) - ((^r1) & r3)
250 j--
251
252 // unmix r1
253 r1 = bits.RotateLeft16(r1, 16-2)
254 r1 = r1 - c.k[j] - (r0 & r3) - ((^r0) & r2)
255 j--
256
257 // unmix r0
258 r0 = bits.RotateLeft16(r0, 16-1)
259 r0 = r0 - c.k[j] - (r3 & r2) - ((^r3) & r1)
260 j--
261
262 }
263
264 binary.LittleEndian.PutUint16(dst[0:], r0)
265 binary.LittleEndian.PutUint16(dst[2:], r1)
266 binary.LittleEndian.PutUint16(dst[4:], r2)
267 binary.LittleEndian.PutUint16(dst[6:], r3)
268 }
269