65 lines
1.8 KiB
C
65 lines
1.8 KiB
C
#include "spn.h"
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unsigned char do_subst(unsigned char w, unsigned char subst[16]) {
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return subst[w];
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}
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unsigned char do_perm(unsigned char w, unsigned char perm[16]) {
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unsigned char result = 0;
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for (int i = 0; i < 8; i++)
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if ((w >> i) & 1)
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result |= (1 << perm[i]);
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return result;
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}
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unsigned short encrypt(unsigned short w, unsigned int key, unsigned char perm[16], unsigned char subst[16]) {
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for (int i = 0; i < 2; i++) {
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unsigned char rk = (key >> (8 * (3 - i))) & 0xFF;
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w ^= (rk << 8) | rk;
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unsigned short tmp = 0;
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for (int j = 0; j < 4; ++j) {
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unsigned char nib = (w >> (j * 4)) & 0xF;
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tmp |= (subst[nib] << (j * 4));
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}
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w = tmp;
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unsigned short permute = 0;
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for (int j = 0; j < 16; ++j)
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if ((w >> j) & 1) {
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permute |= (1 << perm[j]);
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}
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w = permute;
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}
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return w;
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}
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unsigned short decrypt(unsigned short w, unsigned int key, unsigned char perm[16], unsigned char subst[16]) {
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unsigned char inverseSubst[16];
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unsigned char inversePerm[16];
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for (int i = 0; i < 16; ++i) {
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inverseSubst[subst[i]] = i;
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inversePerm[perm [i]] = i;
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}
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for (int i = 1; i >= 0; --i) {
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unsigned short permInverse = 0;
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for (int j = 0; j < 16; ++j)
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if ((w >> j) & 1) {
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permInverse |= (1 << inversePerm[j]);
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}
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w = permInverse;
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unsigned short tmp = 0;
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for (int j = 0; j < 4; ++j) {
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unsigned char sousBloc = (w >> (j * 4)) & 0xF;
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tmp |= (inverseSubst[sousBloc] << (j * 4));
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}
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w = tmp;
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unsigned char rk = (key >> (8 * (3 - i))) & 0xFF;
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w ^= (rk << 8) | rk;
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}
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return w;
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}
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