/* @(#) $Revision: 66.2 $ */
/*LINTLIBRARY*/
/*
* This program implements the
* Proposed Federal Information Processing
* Data Encryption Standard.
* See Federal Register, March 17, 1975 (40FR12134)
*/
/*
* 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 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,
};
/*
* Sequence of shifts used for the key schedule.
*/
static 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 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,
};
void
setkey(key)
char *key;
{
register 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++) {
C[i] = key[PC1_C[i]-1];
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 = C[0];
for(j=0; j < 28-1; j++)
C[j] = C[j+1];
C[27] = t;
t = D[0];
for(j=0; j < 28-1; j++)
D[j] = D[j+1];
D[27] = t;
}
/*
* get Ki. Note C and D are concatenated.
*/
for(j=0; j < 24; j++) {
KS[i][j] = C[PC2_C[j]-1];
KS[i][j+24] = D[PC2_D[j]-28-1];
}
}
/*
* P is a permutation on the selected combination
* of the current L and key.
*/
static 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,
};
/*
* The current block, divided into 2 halves.
*/
static char L[32], R[32];
static char tempL[32];
static char f[32];
/*
* The combination of the key and the input, before selection.
*/
static char preS[48];
void
encrypt(block, edflag)
char *block;
int edflag;
{
int i, ii;
register 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++) {
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[E[j]-1] ^ 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];
}
