* sections 3.8 and 4.2 in http://security.ece.orst.edu/koc/papers/r01rsasw.pdf
*/
+#define OPENSSL_FIPSAPI
+
#include <stdio.h>
#include "cryptlib.h"
#include "bn_lcl.h"
}
}
bn_correct_top(r);
-
- /* mont->ri will be a multiple of the word size */
-#if 0
- BN_rshift(ret,r,mont->ri);
-#else
- if (r->top < ri)
+
+ /* mont->ri will be a multiple of the word size and below code
+ * is kind of BN_rshift(ret,r,mont->ri) equivalent */
+ if (r->top <= ri)
{
ret->top=0;
return(1);
}
al=r->top-ri;
- if (bn_wexpand(ret,al) == NULL) return(0);
+
+#define BRANCH_FREE 1
+#if BRANCH_FREE
+ if (bn_wexpand(ret,ri) == NULL) return(0);
+ x=0-(((al-ri)>>(sizeof(al)*8-1))&1);
+ ret->top=x=(ri&~x)|(al&x); /* min(ri,al) */
ret->neg=r->neg;
+
+ rp=ret->d;
+ ap=&(r->d[ri]);
+
+ {
+ size_t m1,m2;
+
+ v=bn_sub_words(rp,ap,np,ri);
+ /* this ----------------^^ works even in al<ri case
+ * thanks to zealous zeroing of top of the vector in the
+ * beginning. */
+
+ /* if (al==ri && !v) || al>ri) nrp=rp; else nrp=ap; */
+ /* in other words if subtraction result is real, then
+ * trick unconditional memcpy below to perform in-place
+ * "refresh" instead of actual copy. */
+ m1=0-(size_t)(((al-ri)>>(sizeof(al)*8-1))&1); /* al<ri */
+ m2=0-(size_t)(((ri-al)>>(sizeof(al)*8-1))&1); /* al>ri */
+ m1|=m2; /* (al!=ri) */
+ m1|=(0-(size_t)v); /* (al!=ri || v) */
+ m1&=~m2; /* (al!=ri || v) && !al>ri */
+ nrp=(BN_ULONG *)(((PTR_SIZE_INT)rp&~m1)|((PTR_SIZE_INT)ap&m1));
+ }
+
+ /* 'i<ri' is chosen to eliminate dependency on input data, even
+ * though it results in redundant copy in al<ri case. */
+ for (i=0,ri-=4; i<ri; i+=4)
+ {
+ BN_ULONG t1,t2,t3,t4;
+
+ t1=nrp[i+0];
+ t2=nrp[i+1];
+ t3=nrp[i+2]; ap[i+0]=0;
+ t4=nrp[i+3]; ap[i+1]=0;
+ rp[i+0]=t1; ap[i+2]=0;
+ rp[i+1]=t2; ap[i+3]=0;
+ rp[i+2]=t3;
+ rp[i+3]=t4;
+ }
+ for (ri+=4; i<ri; i++)
+ rp[i]=nrp[i], ap[i]=0;
+ bn_correct_top(r);
+ bn_correct_top(ret);
+#else
+ if (bn_wexpand(ret,al) == NULL) return(0);
ret->top=al;
+ ret->neg=r->neg;
rp=ret->d;
ap=&(r->d[ri]);
al+=4;
for (; i<al; i++)
rp[i]=ap[i];
-#endif
if (BN_ucmp(ret, &(mont->N)) >= 0)
{
if (!BN_usub(ret,ret,&(mont->N))) return(0);
}
+#endif
bn_check_top(ret);
return(1);
BN_init(&(ctx->RR));
BN_init(&(ctx->N));
BN_init(&(ctx->Ni));
+ ctx->n0[0] = ctx->n0[1] = 0;
ctx->flags=0;
}
BIGNUM tmod;
BN_ULONG buf[2];
+ BN_init(&tmod);
tmod.d=buf;
tmod.dmax=2;
tmod.neg=0;
mont->ri=(BN_num_bits(mod)+(BN_BITS2-1))/BN_BITS2*BN_BITS2;
#if defined(OPENSSL_BN_ASM_MONT) && (BN_BITS2<=32)
+ /* Only certain BN_BITS2<=32 platforms actually make use of
+ * n0[1], and we could use the #else case (with a shorter R
+ * value) for the others. However, currently only the assembler
+ * files do know which is which. */
+
BN_zero(R);
if (!(BN_set_bit(R,2*BN_BITS2))) goto err;