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/* 7https://www.ietf.org/rfc/rfc2268.txt 8http://people.csail.mit.edu/rivest/pubs/KRRR98.pdf 9 10This code is licensed under the MIT license. 11*/ 12package rc2 13 14import ( 15 "crypto/cipher" 16 "encoding/binary" 17) 18 19// The rc2 block size in bytes 20const BlockSize = 8 21 22type rc2Cipher struct { 23 k [64]uint16 24} 25 26// New returns a new rc2 cipher with the given key and effective key length t1 27func New(key []byte, t1 int) (cipher.Block, error) { 28 // TODO(dgryski): error checking for key length 29 return &rc2Cipher{ 30 k: expandKey(key, t1), 31 }, nil 32} 33 34func (*rc2Cipher) BlockSize() int { return BlockSize } 35 36var piTable = [256]byte{ 37 0xd9, 0x78, 0xf9, 0xc4, 0x19, 0xdd, 0xb5, 0xed, 0x28, 0xe9, 0xfd, 0x79, 0x4a, 0xa0, 0xd8, 0x9d, 38 0xc6, 0x7e, 0x37, 0x83, 0x2b, 0x76, 0x53, 0x8e, 0x62, 0x4c, 0x64, 0x88, 0x44, 0x8b, 0xfb, 0xa2, 39 0x17, 0x9a, 0x59, 0xf5, 0x87, 0xb3, 0x4f, 0x13, 0x61, 0x45, 0x6d, 0x8d, 0x09, 0x81, 0x7d, 0x32, 40 0xbd, 0x8f, 0x40, 0xeb, 0x86, 0xb7, 0x7b, 0x0b, 0xf0, 0x95, 0x21, 0x22, 0x5c, 0x6b, 0x4e, 0x82, 41 0x54, 0xd6, 0x65, 0x93, 0xce, 0x60, 0xb2, 0x1c, 0x73, 0x56, 0xc0, 0x14, 0xa7, 0x8c, 0xf1, 0xdc, 42 0x12, 0x75, 0xca, 0x1f, 0x3b, 0xbe, 0xe4, 0xd1, 0x42, 0x3d, 0xd4, 0x30, 0xa3, 0x3c, 0xb6, 0x26, 43 0x6f, 0xbf, 0x0e, 0xda, 0x46, 0x69, 0x07, 0x57, 0x27, 0xf2, 0x1d, 0x9b, 0xbc, 0x94, 0x43, 0x03, 44 0xf8, 0x11, 0xc7, 0xf6, 0x90, 0xef, 0x3e, 0xe7, 0x06, 0xc3, 0xd5, 0x2f, 0xc8, 0x66, 0x1e, 0xd7, 45 0x08, 0xe8, 0xea, 0xde, 0x80, 0x52, 0xee, 0xf7, 0x84, 0xaa, 0x72, 0xac, 0x35, 0x4d, 0x6a, 0x2a, 46 0x96, 0x1a, 0xd2, 0x71, 0x5a, 0x15, 0x49, 0x74, 0x4b, 0x9f, 0xd0, 0x5e, 0x04, 0x18, 0xa4, 0xec, 47 0xc2, 0xe0, 0x41, 0x6e, 0x0f, 0x51, 0xcb, 0xcc, 0x24, 0x91, 0xaf, 0x50, 0xa1, 0xf4, 0x70, 0x39, 48 0x99, 0x7c, 0x3a, 0x85, 0x23, 0xb8, 0xb4, 0x7a, 0xfc, 0x02, 0x36, 0x5b, 0x25, 0x55, 0x97, 0x31, 49 0x2d, 0x5d, 0xfa, 0x98, 0xe3, 0x8a, 0x92, 0xae, 0x05, 0xdf, 0x29, 0x10, 0x67, 0x6c, 0xba, 0xc9, 50 0xd3, 0x00, 0xe6, 0xcf, 0xe1, 0x9e, 0xa8, 0x2c, 0x63, 0x16, 0x01, 0x3f, 0x58, 0xe2, 0x89, 0xa9, 51 0x0d, 0x38, 0x34, 0x1b, 0xab, 0x33, 0xff, 0xb0, 0xbb, 0x48, 0x0c, 0x5f, 0xb9, 0xb1, 0xcd, 0x2e, 52 0xc5, 0xf3, 0xdb, 0x47, 0xe5, 0xa5, 0x9c, 0x77, 0x0a, 0xa6, 0x20, 0x68, 0xfe, 0x7f, 0xc1, 0xad, 53} 54 55func expandKey(key []byte, t1 int) [64]uint16 { 56 57 l := make([]byte, 128) 58 copy(l, key) 59 60 var t = len(key) 61 var t8 = (t1 + 7) / 8 62 var tm = byte(255 % uint(1<<(8+uint(t1)-8*uint(t8)))) 63 64 for i := len(key); i < 128; i++ { 65 l[i] = piTable[l[i-1]+l[uint8(i-t)]] 66 } 67 68 l[128-t8] = piTable[l[128-t8]&tm] 69 70 for i := 127 - t8; i >= 0; i-- { 71 l[i] = piTable[l[i+1]^l[i+t8]] 72 } 73 74 var k [64]uint16 75 76 for i := range k { 77 k[i] = uint16(l[2*i]) + uint16(l[2*i+1])*256 78 } 79 80 return k 81} 82 83func rotl16(x uint16, b uint) uint16 { 84 return (x >> (16 - b)) | (x << b) 85} 86 87func (c *rc2Cipher) Encrypt(dst, src []byte) { 88 89 r0 := binary.LittleEndian.Uint16(src[0:]) 90 r1 := binary.LittleEndian.Uint16(src[2:]) 91 r2 := binary.LittleEndian.Uint16(src[4:]) 92 r3 := binary.LittleEndian.Uint16(src[6:]) 93 94 var j int 95 96 for j <= 16 { 97 // mix r0 98 r0 = r0 + c.k[j] + (r3 & r2) + ((^r3) & r1) 99 r0 = rotl16(r0, 1) 100 j++ 101 102 // mix r1 103 r1 = r1 + c.k[j] + (r0 & r3) + ((^r0) & r2) 104 r1 = rotl16(r1, 2) 105 j++ 106 107 // mix r2 108 r2 = r2 + c.k[j] + (r1 & r0) + ((^r1) & r3) 109 r2 = rotl16(r2, 3) 110 j++ 111 112 // mix r3 113 r3 = r3 + c.k[j] + (r2 & r1) + ((^r2) & r0) 114 r3 = rotl16(r3, 5) 115 j++ 116 117 } 118 119 r0 = r0 + c.k[r3&63] 120 r1 = r1 + c.k[r0&63] 121 r2 = r2 + c.k[r1&63] 122 r3 = r3 + c.k[r2&63] 123 124 for j <= 40 { 125 // mix r0 126 r0 = r0 + c.k[j] + (r3 & r2) + ((^r3) & r1) 127 r0 = rotl16(r0, 1) 128 j++ 129 130 // mix r1 131 r1 = r1 + c.k[j] + (r0 & r3) + ((^r0) & r2) 132 r1 = rotl16(r1, 2) 133 j++ 134 135 // mix r2 136 r2 = r2 + c.k[j] + (r1 & r0) + ((^r1) & r3) 137 r2 = rotl16(r2, 3) 138 j++ 139 140 // mix r3 141 r3 = r3 + c.k[j] + (r2 & r1) + ((^r2) & r0) 142 r3 = rotl16(r3, 5) 143 j++ 144 145 } 146 147 r0 = r0 + c.k[r3&63] 148 r1 = r1 + c.k[r0&63] 149 r2 = r2 + c.k[r1&63] 150 r3 = r3 + c.k[r2&63] 151 152 for j <= 60 { 153 // mix r0 154 r0 = r0 + c.k[j] + (r3 & r2) + ((^r3) & r1) 155 r0 = rotl16(r0, 1) 156 j++ 157 158 // mix r1 159 r1 = r1 + c.k[j] + (r0 & r3) + ((^r0) & r2) 160 r1 = rotl16(r1, 2) 161 j++ 162 163 // mix r2 164 r2 = r2 + c.k[j] + (r1 & r0) + ((^r1) & r3) 165 r2 = rotl16(r2, 3) 166 j++ 167 168 // mix r3 169 r3 = r3 + c.k[j] + (r2 & r1) + ((^r2) & r0) 170 r3 = rotl16(r3, 5) 171 j++ 172 } 173 174 binary.LittleEndian.PutUint16(dst[0:], r0) 175 binary.LittleEndian.PutUint16(dst[2:], r1) 176 binary.LittleEndian.PutUint16(dst[4:], r2) 177 binary.LittleEndian.PutUint16(dst[6:], r3) 178} 179 180func (c *rc2Cipher) Decrypt(dst, src []byte) { 181 182 r0 := binary.LittleEndian.Uint16(src[0:]) 183 r1 := binary.LittleEndian.Uint16(src[2:]) 184 r2 := binary.LittleEndian.Uint16(src[4:]) 185 r3 := binary.LittleEndian.Uint16(src[6:]) 186 187 j := 63 188 189 for j >= 44 { 190 // unmix r3 191 r3 = rotl16(r3, 16-5) 192 r3 = r3 - c.k[j] - (r2 & r1) - ((^r2) & r0) 193 j-- 194 195 // unmix r2 196 r2 = rotl16(r2, 16-3) 197 r2 = r2 - c.k[j] - (r1 & r0) - ((^r1) & r3) 198 j-- 199 200 // unmix r1 201 r1 = rotl16(r1, 16-2) 202 r1 = r1 - c.k[j] - (r0 & r3) - ((^r0) & r2) 203 j-- 204 205 // unmix r0 206 r0 = rotl16(r0, 16-1) 207 r0 = r0 - c.k[j] - (r3 & r2) - ((^r3) & r1) 208 j-- 209 } 210 211 r3 = r3 - c.k[r2&63] 212 r2 = r2 - c.k[r1&63] 213 r1 = r1 - c.k[r0&63] 214 r0 = r0 - c.k[r3&63] 215 216 for j >= 20 { 217 // unmix r3 218 r3 = rotl16(r3, 16-5) 219 r3 = r3 - c.k[j] - (r2 & r1) - ((^r2) & r0) 220 j-- 221 222 // unmix r2 223 r2 = rotl16(r2, 16-3) 224 r2 = r2 - c.k[j] - (r1 & r0) - ((^r1) & r3) 225 j-- 226 227 // unmix r1 228 r1 = rotl16(r1, 16-2) 229 r1 = r1 - c.k[j] - (r0 & r3) - ((^r0) & r2) 230 j-- 231 232 // unmix r0 233 r0 = rotl16(r0, 16-1) 234 r0 = r0 - c.k[j] - (r3 & r2) - ((^r3) & r1) 235 j-- 236 237 } 238 239 r3 = r3 - c.k[r2&63] 240 r2 = r2 - c.k[r1&63] 241 r1 = r1 - c.k[r0&63] 242 r0 = r0 - c.k[r3&63] 243 244 for j >= 0 { 245 // unmix r3 246 r3 = rotl16(r3, 16-5) 247 r3 = r3 - c.k[j] - (r2 & r1) - ((^r2) & r0) 248 j-- 249 250 // unmix r2 251 r2 = rotl16(r2, 16-3) 252 r2 = r2 - c.k[j] - (r1 & r0) - ((^r1) & r3) 253 j-- 254 255 // unmix r1 256 r1 = rotl16(r1, 16-2) 257 r1 = r1 - c.k[j] - (r0 & r3) - ((^r0) & r2) 258 j-- 259 260 // unmix r0 261 r0 = rotl16(r0, 16-1) 262 r0 = r0 - c.k[j] - (r3 & r2) - ((^r3) & r1) 263 j-- 264 265 } 266 267 binary.LittleEndian.PutUint16(dst[0:], r0) 268 binary.LittleEndian.PutUint16(dst[2:], r1) 269 binary.LittleEndian.PutUint16(dst[4:], r2) 270 binary.LittleEndian.PutUint16(dst[6:], r3) 271} 272