diff options
Diffstat (limited to 'libdes/f_cbc.c')
| -rw-r--r-- | libdes/f_cbc.c | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/libdes/f_cbc.c b/libdes/f_cbc.c new file mode 100644 index 0000000..eba53be --- /dev/null +++ b/libdes/f_cbc.c @@ -0,0 +1,198 @@ +/* + * Copyright (c) 1990 Dennis Ferguson. All rights reserved. + * + * Commercial use is permitted only if products which are derived from + * or include this software are made available for purchase and/or use + * in Canada. Otherwise, redistribution and use in source and binary + * forms are permitted. + */ + +/* + * des_cbc_encrypt.c - an implementation of the DES cipher function in cbc mode + */ +#include "des.h" +#include "f_tables.h" + +/* + * des_cbc_encrypt - {en,de}crypt a stream in CBC mode + */ +int +des_cbc_encrypt(in, out, length, schedule, ivec, encrypt) + des_cblock *in; + des_cblock *out; + long length; + des_key_schedule schedule; + des_cblock ivec; + int encrypt; +{ + register unsigned long left, right; + register unsigned long temp; + register u_int32 *kp; + register unsigned char *ip, *op; + + /* + * Get key pointer here. This won't need to be reinitialized + */ + kp = (u_int32 *)schedule; + + /* + * Deal with encryption and decryption separately. + */ + if (encrypt) { + /* + * Initialize left and right with the contents of the initial + * vector. + */ + ip = (unsigned char *)ivec; + GET_HALF_BLOCK(left, ip); + GET_HALF_BLOCK(right, ip); + + /* + * Suitably initialized, now work the length down 8 bytes + * at a time. + */ + ip = (unsigned char *)in; + op = (unsigned char *)out; + while (length > 0) { + /* + * Get more input, xor it in. If the length is + * greater than or equal to 8 this is straight + * forward. Otherwise we have to fart around. + */ + if (length >= 8) { + left ^= ((*ip++) & 0xff) << 24; + left ^= ((*ip++) & 0xff) << 16; + left ^= ((*ip++) & 0xff) << 8; + left ^= (*ip++) & 0xff; + right ^= ((*ip++) & 0xff) << 24; + right ^= ((*ip++) & 0xff) << 16; + right ^= ((*ip++) & 0xff) << 8; + right ^= (*ip++) & 0xff; + length -= 8; + } else { + /* + * Oh, shoot. We need to pad the + * end with zeroes. Work backwards + * to do this. + */ + ip += (int) length; + switch(length) { + case 7: + right ^= (*(--ip) & 0xff) << 8; + case 6: + right ^= (*(--ip) & 0xff) << 16; + case 5: + right ^= (*(--ip) & 0xff) << 24; + case 4: + left ^= *(--ip) & 0xff; + case 3: + left ^= (*(--ip) & 0xff) << 8; + case 2: + left ^= (*(--ip) & 0xff) << 16; + case 1: + left ^= (*(--ip) & 0xff) << 24; + break; + } + length = 0; + } + + /* + * Encrypt what we have + */ + DES_DO_ENCRYPT(left, right, temp, kp); + + /* + * Copy the results out + */ + PUT_HALF_BLOCK(left, op); + PUT_HALF_BLOCK(right, op); + } + } else { + /* + * Decrypting is harder than encrypting because of + * the necessity of remembering a lot more things. + * Should think about this a little more... + */ + unsigned long ocipherl, ocipherr; + unsigned long cipherl, cipherr; + + if (length <= 0) + return 0; + + /* + * Prime the old cipher with ivec. + */ + ip = (unsigned char *)ivec; + GET_HALF_BLOCK(ocipherl, ip); + GET_HALF_BLOCK(ocipherr, ip); + + /* + * Now do this in earnest until we run out of length. + */ + ip = (unsigned char *)in; + op = (unsigned char *)out; + for (;;) { /* check done inside loop */ + /* + * Read a block from the input into left and + * right. Save this cipher block for later. + */ + GET_HALF_BLOCK(left, ip); + GET_HALF_BLOCK(right, ip); + cipherl = left; + cipherr = right; + + /* + * Decrypt this. + */ + DES_DO_DECRYPT(left, right, temp, kp); + + /* + * Xor with the old cipher to get plain + * text. Output 8 or less bytes of this. + */ + left ^= ocipherl; + right ^= ocipherr; + if (length > 8) { + length -= 8; + PUT_HALF_BLOCK(left, op); + PUT_HALF_BLOCK(right, op); + /* + * Save current cipher block here + */ + ocipherl = cipherl; + ocipherr = cipherr; + } else { + /* + * Trouble here. Start at end of output, + * work backwards. + */ + op += (int) length; + switch(length) { + case 8: + *(--op) = right & 0xff; + case 7: + *(--op) = (right >> 8) & 0xff; + case 6: + *(--op) = (right >> 16) & 0xff; + case 5: + *(--op) = (right >> 24) & 0xff; + case 4: + *(--op) = left & 0xff; + case 3: + *(--op) = (left >> 8) & 0xff; + case 2: + *(--op) = (left >> 16) & 0xff; + case 1: + *(--op) = (left >> 24) & 0xff; + break; + } + break; /* we're done */ + } + } + } + + /* + * Done, return nothing. + */ + return 0; +} |