http://www.jbox.dk/sanos/source/lib/crypt.c.html
//
// crypt.c
//
// DES based implementation of crypt()
//
// Copyright (C) 2005 Michael Ringgaard. All rights reserved.
// Copyright (C) 1999 America Online, Inc. All Rights Reserved.
//
// The contents of this file are subject to the AOLserver Public License
// Version 1.1 (the "License"); you may not use this file except in
// compliance with the License. You may obtain a copy of the License at
// http://aolserver.com/.
//
// Software distributed under the License is distributed on an "AS IS"
// basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
// the License for the specific language governing rights and limitations
// under the License.
//
// The Original Code is AOLserver Code and related documentation
// distributed by AOL.
//
// The Initial Developer of the Original Code is America Online, Inc.
// Portions created by AOL are Copyright (C) 1999 America Online,Inc.
// All Rights Reserved.
//
#include <sys/types.h>
//
// This program implements the Proposed Federal Information Processing Data
// Encryption Standard. See Federal Register, March 17, 1975 (40FR12134)
//
//
// Initial permutation
//
static const char IP[] = {
58, 50, 42, 34, 26, 18, 10, 2,
60, 52, 44, 36, 28, 20, 12, 4,
62, 54, 46, 38, 30, 22, 14, 6,
64, 56, 48, 40, 32, 24, 16, 8,
57, 49, 41, 33, 25, 17, 9, 1,
59, 51, 43, 35, 27, 19, 11, 3,
61, 53, 45, 37, 29, 21, 13, 5,
63, 55, 47, 39, 31, 23, 15, 7,
};
//
// Final permutation, FP = IP^(-1)
//
static const char FP[] = {
40, 8, 48, 16, 56, 24, 64, 32,
39, 7, 47, 15, 55, 23, 63, 31,
38, 6, 46, 14, 54, 22, 62, 30,
37, 5, 45, 13, 53, 21, 61, 29,
36, 4, 44, 12, 52, 20, 60, 28,
35, 3, 43, 11, 51, 19, 59, 27,
34, 2, 42, 10, 50, 18, 58, 26,
33, 1, 41, 9, 49, 17, 57, 25,
};
//
// Permuted-choice 1 from the key bits to yield C and D. Note that bits
// 8,16... are left out: They are intended for a parity check.
//
static const char PC1_C[] = {
57, 49, 41, 33, 25, 17, 9,
1, 58, 50, 42, 34, 26, 18,
10, 2, 59, 51, 43, 35, 27,
19, 11, 3, 60, 52, 44, 36,
};
static const char PC1_D[] = {
63, 55, 47, 39, 31, 23, 15,
7, 62, 54, 46, 38, 30, 22,
14, 6, 61, 53, 45, 37, 29,
21, 13, 5, 28, 20, 12, 4,
};
//
// Sequence of shifts used for the key schedule.
//
static const char shifts[] = {
1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1,
};
//
// Permuted-choice 2, to pick out the bits from the CD array that generate
// the key schedule.
//
static const char PC2_C[] = {
14, 17, 11, 24, 1, 5,
3, 28, 15, 6, 21, 10,
23, 19, 12, 4, 26, 8,
16, 7, 27, 20, 13, 2,
};
static const char PC2_D[] = {
41, 52, 31, 37, 47, 55,
30, 40, 51, 45, 33, 48,
44, 49, 39, 56, 34, 53,
46, 42, 50, 36, 29, 32,
};
//
// The following structure maitains the key schedule.
//
struct sched {
// The C and D arrays used to calculate the key schedule.
char C[28];
char D[28];
// The key schedule. Generated from the key.
char KS[16][48];
// The E bit-selection table.
char E[48];
};
static const char e[] = {
32, 1, 2, 3, 4, 5,
4, 5, 6, 7, 8, 9,
8, 9, 10, 11, 12, 13,
12, 13, 14, 15, 16, 17,
16, 17, 18, 19, 20, 21,
20, 21, 22, 23, 24, 25,
24, 25, 26, 27, 28, 29,
28, 29, 30, 31, 32, 1,
};
//
// Set up the key schedule from the key.
//
static void setkey_r(struct sched *sp, const char *key) {
int i, j, k;
int t;
// First, generate C and D by permuting the key. The low order bit of
// each 8-bit char is not used, so C and D are only 28 bits apiece.
for (i = 0; i < 28; i++) {
sp->C[i] = key[PC1_C[i] - 1];
sp->D[i] = key[PC1_D[i] - 1];
}
// To generate Ki, rotate C and D according to schedule and pick up a
// permutation using PC2.
for (i = 0; i < 16; i++) {
// Rotate
for (k = 0; k < shifts[i]; k++) {
t = sp->C[0];
for (j = 0; j < 28 - 1; j++) sp->C[j] = sp->C[j + 1];
sp->C[27] = t;
t = sp->D[0];
for (j = 0; j < 28 - 1; j++) sp->D[j] = sp->D[j + 1];
sp->D[27] = t;
}
// Get Ki (note C and D are concatenated)
for (j = 0; j < 24; j++) {
sp->KS[i][j] = sp->C[PC2_C[j] - 1];
sp->KS[i][j + 24] = sp->D[PC2_D[j] - 28 - 1];
}
}
for (i = 0; i < 48; i++) sp->E[i] = e[i];
}
//
// The 8 selection functions. For some reason, they give a 0-origin index,
// unlike everything else.
//
static const char S[8][64] = {
{ 14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7,
0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8,
4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0,
15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13 },
{ 15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10,
3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5,
0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15,
13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9 },
{ 10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8,
13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1,
13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7,
1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12 },
{ 7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15,
13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9,
10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4,
3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14 },
{ 2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9,
14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6,
4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14,
11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3 },
{ 12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11,
10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8,
9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6,
4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13 },
{ 4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1,
13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6,
1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2,
6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12 },
{ 13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7,
1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2,
7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8,
2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11 },
};
//
// P is a permutation on the selected combination of the current L and key
//
static const char P[] = {
16, 7, 20, 21,
29, 12, 28, 17,
1, 15, 23, 26,
5, 18, 31, 10,
2, 8, 24, 14,
32, 27, 3, 9,
19, 13, 30, 6,
22, 11, 4, 25,
};
//
// Encrypt a block
//
static void encrypt_r(struct sched *sp, char *block, int edflag) {
// The current block, divided into 2 halves.
char L[64], *R = L + 32;
char tempL[32];
char f[32];
// The combination of the key and the input, before selection
char preS[48];
int i, ii;
int t, j, k;
// First, permute the bits in the input
for (j = 0; j < 64; j++) L[j] = block[IP[j] - 1];
// Perform an encryption operation 16 times
for (ii = 0; ii < 16; ii++) {
// Set direction
if (edflag) {
i = 15 - ii;
} else {
i = ii;
}
// Save the R array, which will be the new L
for (j = 0; j < 32; j++) tempL[j] = R[j];
// Expand R to 48 bits using the E selector; exclusive-or with the current key bits
for (j = 0; j < 48; j++) preS[j] = R[sp->E[j] - 1] ^ sp->KS[i][j];
// The pre-select bits are now considered in 8 groups of 6 bits each.
// The 8 selection functions map these 6-bit quantities into 4-bit
// quantities and the results permuted to make an f(R, K). The
// indexing into the selection functions is peculiar; it could be
// simplified by rewriting the tables.
for (j = 0; j < 8; j++) {
t = 6 * j;
k = S[j][(preS[t + 0] << 5) +
(preS[t + 1] << 3) +
(preS[t + 2] << 2) +
(preS[t + 3] << 1) +
(preS[t + 4] << 0) +
(preS[t + 5] << 4)];
t = 4 * j;
f[t + 0] = (k >> 3) & 01;
f[t + 1] = (k >> 2) & 01;
f[t + 2] = (k >> 1) & 01;
f[t + 3] = (k >> 0) & 01;
}
// The new R is L ^ f(R, K). The f here has to be permuted first, though.
for (j = 0; j < 32; j++) R[j] = L[j] ^ f[P[j] - 1];
// Finally, the new L (the original R) is copied back.
for (j = 0; j < 32; j++) L[j] = tempL[j];
}
// The output L and R are reversed.
for (j = 0; j < 32; j++) {
t = L[j];
L[j] = R[j];
R[j] = t;
}
// The final output gets the inverse permutation of the very original.
for (j = 0; j < 64; j++) block[j] = L[FP[j] - 1];
}
char *crypt_r(const char *key, const char *salt, char *buf) {
int i, j, c;
int temp;
char block[66];
struct sched s;
for (i = 0; i < 66; i++) block[i] = 0;
for (i = 0; (c = *key) && i < 64; key++) {
for (j = 0; j < 7; j++, i++) block[i] = (c >> (6 - j)) & 01;
i++;
}
setkey_r(&s, block);
for (i = 0; i < 66; i++) block[i] = 0;
for (i = 0; i < 2; i++) {
c = *salt++;
buf[i] = c;
if (c > 'Z') c -= 6;
if (c > '9') c -= 7;
c -= '.';
for (j = 0; j < 6; j++) {
if ((c >> j) & 01) {
temp = s.E[6 * i + j];
s.E[6 * i + j] = s.E[6 * i + j + 24];
s.E[6 * i + j + 24] = temp;
}
}
}
for (i = 0; i < 25; i++) encrypt_r(&s, block, 0);
for (i = 0; i < 11; i++) {
c = 0;
for (j = 0; j < 6; j++) {
c <<= 1;
c |= block[6 * i + j];
}
c += '.';
if (c > '9') c += 7;
if (c > 'Z') c += 6;
buf[i + 2] = c;
}
buf[i + 2] = 0;
if (buf[1] == 0) buf[1] = buf[0];
return buf;
}