Problem - Kevin Tafuro

typedef struct {
struct hash127 hctx;
SPC_KEY_SCHED ekey;
SPC_KEY_SCHED nkey;
} SPC_MAC127_CTX;
void spc_mac127_init(SPC_MAC127_CTX *ctx, unsigned char key[16]) {
int i;
unsigned char pt[16] = {0, };
volatile int32 hk[4];
volatile unsigned char ek[16], nk[16];
SPC_ENCRYPT_INIT(&(ctx->ekey), key, 16);
SPC_DO_ENCRYPT(&(ctx->ekey), pt, (unsigned char *)ek);
pt[15] = 1;
SPC_DO_ENCRYPT(&(ctx->ekey), pt, (unsigned char *)nk);
pt[15] = 2;
SPC_DO_ENCRYPT(&(ctx->ekey), pt, (unsigned char *)hk);
SPC_ENCRYPT_INIT(&(ctx->ekey), (unsigned char *)ek, 16);
SPC_ENCRYPT_INIT(&(ctx->nkey), (unsigned char *)nk, 16);
hk[0] = htonl(hk[0]);
hk[1] = htonl(hk[1]);
hk[2] = htonl(hk[2]);
hk[3] = htonl(hk[3]);
hash127_expand(&(ctx->hctx), (int32 *)hk);
hk[0] = hk[1] = hk[2] = hk[3] = 0;
for (i = 0; i < 16; i++) ek[i] = nk[i] = 0;
}
void spc_mac127(SPC_MAC127_CTX *c, unsigned char *msg, size_t mlen,
unsigned char nonce[16], unsigned char out[16]) {
int i, r = mlen % 4; /* leftover bytes to stick into final block */
int32 x[4] = {0,};
for (i = 0; i hctx), x);
x[0] = htonl(*(int *)out);
x[1] = htonl(*(int *)(out + 4));
x[2] = htonl(*(int *)(out + 8));
x[3] = htonl(*(int *)(out + 12));
SPC_DO_ENCRYPT(&(c->ekey), out, out);
SPC_DO_ENCRYPT(&(c->nkey), nonce, (unsigned char *)x);
((int32 *)out)[0] ^= x[0];
((int32 *)out)[1] ^= x[1];
((int32 *)out)[2] ^= x[2];
((int32 *)out)[3] ^= x[3];
}
See Also
• hash127 home page: http://cr.yp.to/hash127.html
• Recipes 6.9, 6.12, 6.13
290 | Chapter 6: Hashes and Message Authentication
This is the Title of the Book, eMatter Edition
Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.