rc2.go 6.2 KB

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  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. // Package rc2 implements the RC2 cipher
  5. /*
  6. https://www.ietf.org/rfc/rfc2268.txt
  7. http://people.csail.mit.edu/rivest/pubs/KRRR98.pdf
  8. This code is licensed under the MIT license.
  9. */
  10. package rc2
  11. import (
  12. "crypto/cipher"
  13. "encoding/binary"
  14. )
  15. // The rc2 block size in bytes
  16. const BlockSize = 8
  17. type rc2Cipher struct {
  18. k [64]uint16
  19. }
  20. // New returns a new rc2 cipher with the given key and effective key length t1
  21. func New(key []byte, t1 int) (cipher.Block, error) {
  22. // TODO(dgryski): error checking for key length
  23. return &rc2Cipher{
  24. k: expandKey(key, t1),
  25. }, nil
  26. }
  27. func (*rc2Cipher) BlockSize() int { return BlockSize }
  28. var piTable = [256]byte{
  29. 0xd9, 0x78, 0xf9, 0xc4, 0x19, 0xdd, 0xb5, 0xed, 0x28, 0xe9, 0xfd, 0x79, 0x4a, 0xa0, 0xd8, 0x9d,
  30. 0xc6, 0x7e, 0x37, 0x83, 0x2b, 0x76, 0x53, 0x8e, 0x62, 0x4c, 0x64, 0x88, 0x44, 0x8b, 0xfb, 0xa2,
  31. 0x17, 0x9a, 0x59, 0xf5, 0x87, 0xb3, 0x4f, 0x13, 0x61, 0x45, 0x6d, 0x8d, 0x09, 0x81, 0x7d, 0x32,
  32. 0xbd, 0x8f, 0x40, 0xeb, 0x86, 0xb7, 0x7b, 0x0b, 0xf0, 0x95, 0x21, 0x22, 0x5c, 0x6b, 0x4e, 0x82,
  33. 0x54, 0xd6, 0x65, 0x93, 0xce, 0x60, 0xb2, 0x1c, 0x73, 0x56, 0xc0, 0x14, 0xa7, 0x8c, 0xf1, 0xdc,
  34. 0x12, 0x75, 0xca, 0x1f, 0x3b, 0xbe, 0xe4, 0xd1, 0x42, 0x3d, 0xd4, 0x30, 0xa3, 0x3c, 0xb6, 0x26,
  35. 0x6f, 0xbf, 0x0e, 0xda, 0x46, 0x69, 0x07, 0x57, 0x27, 0xf2, 0x1d, 0x9b, 0xbc, 0x94, 0x43, 0x03,
  36. 0xf8, 0x11, 0xc7, 0xf6, 0x90, 0xef, 0x3e, 0xe7, 0x06, 0xc3, 0xd5, 0x2f, 0xc8, 0x66, 0x1e, 0xd7,
  37. 0x08, 0xe8, 0xea, 0xde, 0x80, 0x52, 0xee, 0xf7, 0x84, 0xaa, 0x72, 0xac, 0x35, 0x4d, 0x6a, 0x2a,
  38. 0x96, 0x1a, 0xd2, 0x71, 0x5a, 0x15, 0x49, 0x74, 0x4b, 0x9f, 0xd0, 0x5e, 0x04, 0x18, 0xa4, 0xec,
  39. 0xc2, 0xe0, 0x41, 0x6e, 0x0f, 0x51, 0xcb, 0xcc, 0x24, 0x91, 0xaf, 0x50, 0xa1, 0xf4, 0x70, 0x39,
  40. 0x99, 0x7c, 0x3a, 0x85, 0x23, 0xb8, 0xb4, 0x7a, 0xfc, 0x02, 0x36, 0x5b, 0x25, 0x55, 0x97, 0x31,
  41. 0x2d, 0x5d, 0xfa, 0x98, 0xe3, 0x8a, 0x92, 0xae, 0x05, 0xdf, 0x29, 0x10, 0x67, 0x6c, 0xba, 0xc9,
  42. 0xd3, 0x00, 0xe6, 0xcf, 0xe1, 0x9e, 0xa8, 0x2c, 0x63, 0x16, 0x01, 0x3f, 0x58, 0xe2, 0x89, 0xa9,
  43. 0x0d, 0x38, 0x34, 0x1b, 0xab, 0x33, 0xff, 0xb0, 0xbb, 0x48, 0x0c, 0x5f, 0xb9, 0xb1, 0xcd, 0x2e,
  44. 0xc5, 0xf3, 0xdb, 0x47, 0xe5, 0xa5, 0x9c, 0x77, 0x0a, 0xa6, 0x20, 0x68, 0xfe, 0x7f, 0xc1, 0xad,
  45. }
  46. func expandKey(key []byte, t1 int) [64]uint16 {
  47. l := make([]byte, 128)
  48. copy(l, key)
  49. var t = len(key)
  50. var t8 = (t1 + 7) / 8
  51. var tm = byte(255 % uint(1<<(8+uint(t1)-8*uint(t8))))
  52. for i := len(key); i < 128; i++ {
  53. l[i] = piTable[l[i-1]+l[uint8(i-t)]]
  54. }
  55. l[128-t8] = piTable[l[128-t8]&tm]
  56. for i := 127 - t8; i >= 0; i-- {
  57. l[i] = piTable[l[i+1]^l[i+t8]]
  58. }
  59. var k [64]uint16
  60. for i := range k {
  61. k[i] = uint16(l[2*i]) + uint16(l[2*i+1])*256
  62. }
  63. return k
  64. }
  65. func rotl16(x uint16, b uint) uint16 {
  66. return (x >> (16 - b)) | (x << b)
  67. }
  68. func (c *rc2Cipher) Encrypt(dst, src []byte) {
  69. r0 := binary.LittleEndian.Uint16(src[0:])
  70. r1 := binary.LittleEndian.Uint16(src[2:])
  71. r2 := binary.LittleEndian.Uint16(src[4:])
  72. r3 := binary.LittleEndian.Uint16(src[6:])
  73. var j int
  74. for j <= 16 {
  75. // mix r0
  76. r0 = r0 + c.k[j] + (r3 & r2) + ((^r3) & r1)
  77. r0 = rotl16(r0, 1)
  78. j++
  79. // mix r1
  80. r1 = r1 + c.k[j] + (r0 & r3) + ((^r0) & r2)
  81. r1 = rotl16(r1, 2)
  82. j++
  83. // mix r2
  84. r2 = r2 + c.k[j] + (r1 & r0) + ((^r1) & r3)
  85. r2 = rotl16(r2, 3)
  86. j++
  87. // mix r3
  88. r3 = r3 + c.k[j] + (r2 & r1) + ((^r2) & r0)
  89. r3 = rotl16(r3, 5)
  90. j++
  91. }
  92. r0 = r0 + c.k[r3&63]
  93. r1 = r1 + c.k[r0&63]
  94. r2 = r2 + c.k[r1&63]
  95. r3 = r3 + c.k[r2&63]
  96. for j <= 40 {
  97. // mix r0
  98. r0 = r0 + c.k[j] + (r3 & r2) + ((^r3) & r1)
  99. r0 = rotl16(r0, 1)
  100. j++
  101. // mix r1
  102. r1 = r1 + c.k[j] + (r0 & r3) + ((^r0) & r2)
  103. r1 = rotl16(r1, 2)
  104. j++
  105. // mix r2
  106. r2 = r2 + c.k[j] + (r1 & r0) + ((^r1) & r3)
  107. r2 = rotl16(r2, 3)
  108. j++
  109. // mix r3
  110. r3 = r3 + c.k[j] + (r2 & r1) + ((^r2) & r0)
  111. r3 = rotl16(r3, 5)
  112. j++
  113. }
  114. r0 = r0 + c.k[r3&63]
  115. r1 = r1 + c.k[r0&63]
  116. r2 = r2 + c.k[r1&63]
  117. r3 = r3 + c.k[r2&63]
  118. for j <= 60 {
  119. // mix r0
  120. r0 = r0 + c.k[j] + (r3 & r2) + ((^r3) & r1)
  121. r0 = rotl16(r0, 1)
  122. j++
  123. // mix r1
  124. r1 = r1 + c.k[j] + (r0 & r3) + ((^r0) & r2)
  125. r1 = rotl16(r1, 2)
  126. j++
  127. // mix r2
  128. r2 = r2 + c.k[j] + (r1 & r0) + ((^r1) & r3)
  129. r2 = rotl16(r2, 3)
  130. j++
  131. // mix r3
  132. r3 = r3 + c.k[j] + (r2 & r1) + ((^r2) & r0)
  133. r3 = rotl16(r3, 5)
  134. j++
  135. }
  136. binary.LittleEndian.PutUint16(dst[0:], r0)
  137. binary.LittleEndian.PutUint16(dst[2:], r1)
  138. binary.LittleEndian.PutUint16(dst[4:], r2)
  139. binary.LittleEndian.PutUint16(dst[6:], r3)
  140. }
  141. func (c *rc2Cipher) Decrypt(dst, src []byte) {
  142. r0 := binary.LittleEndian.Uint16(src[0:])
  143. r1 := binary.LittleEndian.Uint16(src[2:])
  144. r2 := binary.LittleEndian.Uint16(src[4:])
  145. r3 := binary.LittleEndian.Uint16(src[6:])
  146. j := 63
  147. for j >= 44 {
  148. // unmix r3
  149. r3 = rotl16(r3, 16-5)
  150. r3 = r3 - c.k[j] - (r2 & r1) - ((^r2) & r0)
  151. j--
  152. // unmix r2
  153. r2 = rotl16(r2, 16-3)
  154. r2 = r2 - c.k[j] - (r1 & r0) - ((^r1) & r3)
  155. j--
  156. // unmix r1
  157. r1 = rotl16(r1, 16-2)
  158. r1 = r1 - c.k[j] - (r0 & r3) - ((^r0) & r2)
  159. j--
  160. // unmix r0
  161. r0 = rotl16(r0, 16-1)
  162. r0 = r0 - c.k[j] - (r3 & r2) - ((^r3) & r1)
  163. j--
  164. }
  165. r3 = r3 - c.k[r2&63]
  166. r2 = r2 - c.k[r1&63]
  167. r1 = r1 - c.k[r0&63]
  168. r0 = r0 - c.k[r3&63]
  169. for j >= 20 {
  170. // unmix r3
  171. r3 = rotl16(r3, 16-5)
  172. r3 = r3 - c.k[j] - (r2 & r1) - ((^r2) & r0)
  173. j--
  174. // unmix r2
  175. r2 = rotl16(r2, 16-3)
  176. r2 = r2 - c.k[j] - (r1 & r0) - ((^r1) & r3)
  177. j--
  178. // unmix r1
  179. r1 = rotl16(r1, 16-2)
  180. r1 = r1 - c.k[j] - (r0 & r3) - ((^r0) & r2)
  181. j--
  182. // unmix r0
  183. r0 = rotl16(r0, 16-1)
  184. r0 = r0 - c.k[j] - (r3 & r2) - ((^r3) & r1)
  185. j--
  186. }
  187. r3 = r3 - c.k[r2&63]
  188. r2 = r2 - c.k[r1&63]
  189. r1 = r1 - c.k[r0&63]
  190. r0 = r0 - c.k[r3&63]
  191. for j >= 0 {
  192. // unmix r3
  193. r3 = rotl16(r3, 16-5)
  194. r3 = r3 - c.k[j] - (r2 & r1) - ((^r2) & r0)
  195. j--
  196. // unmix r2
  197. r2 = rotl16(r2, 16-3)
  198. r2 = r2 - c.k[j] - (r1 & r0) - ((^r1) & r3)
  199. j--
  200. // unmix r1
  201. r1 = rotl16(r1, 16-2)
  202. r1 = r1 - c.k[j] - (r0 & r3) - ((^r0) & r2)
  203. j--
  204. // unmix r0
  205. r0 = rotl16(r0, 16-1)
  206. r0 = r0 - c.k[j] - (r3 & r2) - ((^r3) & r1)
  207. j--
  208. }
  209. binary.LittleEndian.PutUint16(dst[0:], r0)
  210. binary.LittleEndian.PutUint16(dst[2:], r1)
  211. binary.LittleEndian.PutUint16(dst[4:], r2)
  212. binary.LittleEndian.PutUint16(dst[6:], r3)
  213. }