2 * Copyright 1985, 1986, 1987, 1988 by the Massachusetts Institute
5 * For copying and distribution information, please see the file
8 * These routines perform encryption and decryption using the DES
9 * private key algorithm, or else a subset of it-- fewer inner loops.
10 * ( AUTH_DES_ITER defaults to 16, may be less)
12 * Under U.S. law, this software may not be exported outside the US
13 * without license from the U.S. Commerce department.
15 * The key schedule is passed as an arg, as well as the cleartext or
16 * ciphertext. The cleartext and ciphertext should be in host order.
18 * These routines form the library interface to the des facilities.
20 * spm 8/85 MIT project athena
23 #include <mit-cpyright.h>
28 #include <afsconfig.h>
29 #include <afs/param.h>
30 #include "des_prototypes.h"
35 #include "des_internal.h"
37 #define XPRT_PCBC_ENCRYPT
40 * pcbc_encrypt is an "error propagation chaining" encrypt operation
41 * for DES, similar to CBC, but that, on encryption, "xor"s the
42 * plaintext of block N with the ciphertext resulting from block N,
43 * then "xor"s that result with the plaintext of block N+1 prior to
44 * encrypting block N+1. (decryption the appropriate inverse. This
45 * "pcbc" mode propagates a single bit error anywhere in either the
46 * cleartext or ciphertext chain all the way through to the end. In
47 * contrast, CBC mode limits a single bit error in the ciphertext to
48 * affect only the current (8byte) block and the subsequent block.
50 * performs pcbc error-propagation chaining operation by xor-ing block
51 * N+1 with both the plaintext (block N) and the ciphertext from block
52 * N. Either encrypts from cleartext to ciphertext, if encrypt != 0
53 * or decrypts from ciphertext to cleartext, if encrypt == 0
55 * NOTE-- the output is ALWAYS an multiple of 8 bytes long. If not
56 * enough space was provided, your program will get trashed.
58 * For encryption, the cleartext string is null padded, at the end, to
59 * an integral multiple of eight bytes.
61 * For decryption, the ciphertext will be used in integral multiples
62 * of 8 bytes, but only the first "length" bytes returned into the
65 * This is NOT a standard mode of operation.
69 des_cblock *in; * >= length bytes of input text *
70 des_cblock *out; * >= length bytes of output text *
71 register afs_int32 length; * in bytes *
72 int encrypt; * 0 ==> decrypt, else encrypt *
73 des_key_schedule key; * precomputed key schedule *
74 des_cblock *iv; * 8 bytes of ivec *
77 des_pcbc_encrypt(des_cblock * in, des_cblock * out, register afs_int32 length,
78 des_key_schedule key, des_cblock * iv, int encrypt)
80 register afs_uint32 *input = (afs_uint32 *) in;
81 register afs_uint32 *output = (afs_uint32 *) out;
82 register afs_uint32 *ivec = (afs_uint32 *) iv;
85 afs_uint32 t_input[2];
86 afs_uint32 t_output[2];
87 unsigned char *t_in_p = (unsigned char *)t_input;
88 afs_uint32 xor_0, xor_1;
92 if ((afs_int32) ivec & 3) {
93 memcpy((char *)&xor_0, (char *)ivec++, sizeof(xor_0));
94 memcpy((char *)&xor_1, (char *)ivec, sizeof(xor_1));
102 for (i = 0; length > 0; i++, length -= 8) {
105 if ((afs_int32) input & 3) {
106 memcpy((char *)&t_input[0], (char *)input,
108 memcpy((char *)&t_input[1], (char *)(input + 1),
114 t_input[1] = *(input + 1);
119 for (j = length; j <= 7; j++)
124 des_debug_print("clear", length, t_input[0], t_input[1]);
126 /* do the xor for cbc into the temp */
130 (void)des_ecb_encrypt(t_input, t_output, key, encrypt);
133 * We want to XOR with both the plaintext and ciphertext
134 * of the previous block, before we write the output, in
135 * case both input and output are the same space.
138 if ((afs_int32) input & 3) {
139 memcpy((char *)&xor_0, (char *)input++, sizeof(xor_0));
140 xor_0 ^= t_output[0];
141 memcpy((char *)&xor_1, (char *)input++, sizeof(xor_1));
142 xor_1 ^= t_output[1];
146 xor_0 = *input++ ^ t_output[0];
147 xor_1 = *input++ ^ t_output[1];
151 /* copy temp output and save it for cbc */
153 if ((afs_int32) output & 3) {
154 memcpy((char *)output++, (char *)&t_output[0],
155 sizeof(t_output[0]));
156 memcpy((char *)output++, (char *)&t_output[1],
157 sizeof(t_output[1]));
161 *output++ = t_output[0];
162 *output++ = t_output[1];
167 des_debug_print("xor'ed", i, t_input[0], t_input[1]);
168 des_debug_print("cipher", i, t_output[0], t_output[1]);
182 if ((afs_int32) ivec & 3) {
183 memcpy((char *)&xor_0, (char *)ivec++, sizeof(xor_0));
184 memcpy((char *)&xor_1, (char *)ivec, sizeof(xor_1));
192 for (i = 0; length > 0; i++, length -= 8) {
195 if ((afs_int32) input & 3) {
196 memcpy((char *)&t_input[0], (char *)input++,
198 memcpy((char *)&t_input[1], (char *)input++,
203 t_input[0] = *input++;
204 t_input[1] = *input++;
207 /* no padding for decrypt */
210 des_debug_print("cipher", i, t_input[0], t_input[1]);
217 (void)des_ecb_encrypt(t_input, t_output, key, encrypt);
220 des_debug_print("out pre xor", i, t_output[0], t_output[1]);
222 /* do the xor for cbc into the output */
223 t_output[0] ^= xor_0;
224 t_output[1] ^= xor_1;
225 /* copy temp output */
227 if ((afs_int32) output & 3) {
228 memcpy((char *)output++, (char *)&t_output[0],
229 sizeof(t_output[0]));
230 memcpy((char *)output++, (char *)&t_output[1],
231 sizeof(t_output[1]));
235 *output++ = t_output[0];
236 *output++ = t_output[1];
239 /* save xor value for next round */
240 xor_0 = t_output[0] ^ t_input[0];
241 xor_1 = t_output[1] ^ t_input[1];
245 des_debug_print("clear", i, t_output[0], t_output[1]);