| 72 | } |
| 73 | |
| 74 | void ChaCha20::Keystream(unsigned char* c, size_t bytes) |
| 75 | { |
| 76 | uint32_t x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15; |
| 77 | uint32_t j0, j1, j2, j3, j4, j5, j6, j7, j8, j9, j10, j11, j12, j13, j14, j15; |
| 78 | unsigned char *ctarget = nullptr; |
| 79 | unsigned char tmp[64]; |
| 80 | unsigned int i; |
| 81 | |
| 82 | if (!bytes) return; |
| 83 | |
| 84 | j0 = input[0]; |
| 85 | j1 = input[1]; |
| 86 | j2 = input[2]; |
| 87 | j3 = input[3]; |
| 88 | j4 = input[4]; |
| 89 | j5 = input[5]; |
| 90 | j6 = input[6]; |
| 91 | j7 = input[7]; |
| 92 | j8 = input[8]; |
| 93 | j9 = input[9]; |
| 94 | j10 = input[10]; |
| 95 | j11 = input[11]; |
| 96 | j12 = input[12]; |
| 97 | j13 = input[13]; |
| 98 | j14 = input[14]; |
| 99 | j15 = input[15]; |
| 100 | |
| 101 | for (;;) { |
| 102 | if (bytes < 64) { |
| 103 | ctarget = c; |
| 104 | c = tmp; |
| 105 | } |
| 106 | x0 = j0; |
| 107 | x1 = j1; |
| 108 | x2 = j2; |
| 109 | x3 = j3; |
| 110 | x4 = j4; |
| 111 | x5 = j5; |
| 112 | x6 = j6; |
| 113 | x7 = j7; |
| 114 | x8 = j8; |
| 115 | x9 = j9; |
| 116 | x10 = j10; |
| 117 | x11 = j11; |
| 118 | x12 = j12; |
| 119 | x13 = j13; |
| 120 | x14 = j14; |
| 121 | x15 = j15; |
| 122 | for (i = 20;i > 0;i -= 2) { |
| 123 | QUARTERROUND( x0, x4, x8,x12) |
| 124 | QUARTERROUND( x1, x5, x9,x13) |
| 125 | QUARTERROUND( x2, x6,x10,x14) |
| 126 | QUARTERROUND( x3, x7,x11,x15) |
| 127 | QUARTERROUND( x0, x5,x10,x15) |
| 128 | QUARTERROUND( x1, x6,x11,x12) |
| 129 | QUARTERROUND( x2, x7, x8,x13) |
| 130 | QUARTERROUND( x3, x4, x9,x14) |
| 131 | } |