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Annotation of researchv10no/cmd/descrypt/des.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  *     Data Encryption Standard (DES) Layer
                      3:  *     D.P.Mitchell  83/06/08.
                      4:  */
                      5: 
                      6: #include "crypt.h"
                      7: 
                      8: extern long s0p[],s1p[],s2p[],s3p[],s4p[],s5p[],s6p[],s7p[];
                      9: extern int subkeys[];
                     10: 
                     11: des(block)
                     12: Block *block;
                     13: {
                     14:        register long crypto, temp;
                     15:        register int *key;
                     16:        register round;
                     17:        register long right, left;
                     18: 
                     19:        left = block->left;
                     20:        right = block->right;
                     21:        key = subkeys;
                     22:        for (round = 0; round < 16; round++) {
                     23:                temp = (right << 1) | ((right >> 31) & 1);
                     24:                crypto  = s0p[(temp & 0x3f) ^ *key++];
                     25:                crypto |= s1p[((temp & 0x3f0) >> 4) ^ *key++];
                     26:                crypto |= s2p[((temp & 0x3f00) >> 8) ^ *key++];
                     27:                crypto |= s3p[((temp & 0x3f000) >> 12) ^ *key++];
                     28:                crypto |= s4p[((temp & 0x3f0000) >> 16) ^ *key++];
                     29:                crypto |= s5p[((temp & 0x3f00000) >> 20) ^ *key++];
                     30:                crypto |= s6p[((temp & 0x3f000000) >> 24) ^ *key++];
                     31:                temp = ((right & 1) << 5) | ((right >> 27) & 0x1f);
                     32:                crypto |= s7p[temp ^ *key++];
                     33:                if (round == 15)
                     34:                        left ^= crypto;
                     35:                else {
                     36:                        temp = left;
                     37:                        left = right;
                     38:                        right = temp ^ crypto;
                     39:                }
                     40:        }
                     41:        block->left = left;
                     42:        block->right = right;
                     43: }

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