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Remove redundant BN_ucmp, fix boundary condition in BN_nist_mod_224 and

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reimplement BN_nist_mod_521.
This commit is contained in:
Andy Polyakov 2008-10-15 10:47:48 +00:00
parent 28b6d5020e
commit 762a2e3cab
1 changed files with 44 additions and 75 deletions
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119
crypto/bn/bn_nist.c
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@ -345,11 +345,6 @@ int BN_nist_mod_192(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
r->top = BN_NIST_192_TOP; r->top = BN_NIST_192_TOP;
bn_correct_top(r); bn_correct_top(r);
if (BN_ucmp(field, r) <= 0)
{
if (!BN_usub(r, r, field)) return 0;
}
return 1; return 1;
} }
@ -381,7 +376,7 @@ int BN_nist_mod_224(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
field = &_bignum_nist_p_224; /* just to make sure */ field = &_bignum_nist_p_224; /* just to make sure */
if (BN_is_negative(a) || a->top > 2*BN_NIST_224_TOP) if (BN_is_negative(a) || a->top > (2*224+BN_BITS2-1)/BN_BITS2)
return BN_nnmod(r, field, a, ctx); return BN_nnmod(r, field, a, ctx);
i = BN_ucmp(field, a); i = BN_ucmp(field, a);
@ -456,11 +451,6 @@ int BN_nist_mod_224(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
r->top = BN_NIST_224_TOP; r->top = BN_NIST_224_TOP;
bn_correct_top(r); bn_correct_top(r);
if (BN_ucmp(field, r) <= 0)
{
if (!BN_usub(r, r, field)) return 0;
}
return 1; return 1;
} }
@ -574,11 +564,6 @@ int BN_nist_mod_256(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
r->top = BN_NIST_256_TOP; r->top = BN_NIST_256_TOP;
bn_correct_top(r); bn_correct_top(r);
if (BN_ucmp(field, r) <= 0)
{
if (!BN_usub(r, r, field)) return 0;
}
return 1; return 1;
} }
@ -698,81 +683,65 @@ int BN_nist_mod_384(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
r->top = BN_NIST_384_TOP; r->top = BN_NIST_384_TOP;
bn_correct_top(r); bn_correct_top(r);
if (BN_ucmp(field, r) <= 0)
{
if (!BN_usub(r, r, field)) return 0;
}
return 1; return 1;
} }
#define BN_NIST_521_RSHIFT (521%BN_BITS2)
#define BN_NIST_521_LSHIFT (BN_BITS2-BN_NIST_521_RSHIFT)
#define BN_NIST_521_TOP_MASK ((BN_ULONG)BN_MASK2>>BN_NIST_521_LSHIFT)
int BN_nist_mod_521(BIGNUM *r, const BIGNUM *a, const BIGNUM *field, int BN_nist_mod_521(BIGNUM *r, const BIGNUM *a, const BIGNUM *field,
BN_CTX *ctx) BN_CTX *ctx)
{ {
#if BN_BITS2 == 64 int top = a->top, i;
#define BN_NIST_521_TOP_MASK (BN_ULONG)0x1FF BN_ULONG *r_d, *a_d = a->d,
#elif BN_BITS2 == 32 t_d[BN_NIST_521_TOP],
#define BN_NIST_521_TOP_MASK (BN_ULONG)0x1FF val,tmp,*res;
#endif size_t mask;
int top, ret = 0;
BIGNUM *tmp;
field = &_bignum_nist_p_521; /* just to make sure */ field = &_bignum_nist_p_521; /* just to make sure */
if (BN_is_negative(a)) if (BN_is_negative(a) || BN_num_bits(a)>2*521)
return BN_nnmod(r, field, a, ctx); return BN_nnmod(r, field, a, ctx);
/* check whether a reduction is necessary */ i = BN_ucmp(field, a);
top = a->top; if (i == 0)
if (top < BN_NIST_521_TOP || ( top == BN_NIST_521_TOP &&
(!(a->d[BN_NIST_521_TOP-1] & ~(BN_NIST_521_TOP_MASK)))))
{ {
int i = BN_ucmp(field, a); BN_zero(r);
if (i == 0) return 1;
{
BN_zero(r);
return 1;
}
else
{
#ifdef BN_DEBUG
OPENSSL_assert(i > 0); /* because 'field' is 1111...1111 */
#endif
return (r == a)? 1 : (BN_copy(r ,a) != NULL);
}
} }
else if (i > 0)
return (r == a)? 1 : (BN_copy(r ,a) != NULL);
if (BN_num_bits(a) > 2*521) if (r != a)
return BN_nnmod(r, field, a, ctx);
BN_CTX_start(ctx);
tmp = BN_CTX_get(ctx);
if (!tmp)
goto err;
if (!bn_wexpand(tmp, BN_NIST_521_TOP))
goto err;
nist_cp_bn(tmp->d, a->d, BN_NIST_521_TOP);
tmp->top = BN_NIST_521_TOP;
tmp->d[BN_NIST_521_TOP-1] &= BN_NIST_521_TOP_MASK;
bn_correct_top(tmp);
if (!BN_rshift(r, a, 521))
goto err;
if (!BN_uadd(r, tmp, r))
goto err;
if (BN_ucmp(field, r) <= 0)
{ {
if (!BN_usub(r, r, field)) goto err; if (!bn_wexpand(r,BN_NIST_521_TOP))
return 0;
r_d = r->d;
nist_cp_bn(r_d,a_d, BN_NIST_521_TOP);
} }
else
r_d = a_d;
ret = 1; /* upper 521 bits, copy ... */
err: nist_cp_bn_0(t_d,a_d + (BN_NIST_521_TOP-1), top - (BN_NIST_521_TOP-1),BN_NIST_521_TOP);
BN_CTX_end(ctx); /* ... and right shift */
for (val=t_d[0],i=0; i<BN_NIST_521_TOP-1; i++)
{
tmp = val>>BN_NIST_521_RSHIFT;
val = t_d[i+1];
t_d[i] = (tmp | val<<BN_NIST_521_LSHIFT) & BN_MASK2;
}
t_d[i] = val>>BN_NIST_521_RSHIFT;
/* lower 521 bits */
r_d[i] &= BN_NIST_521_TOP_MASK;
bn_check_top(r); bn_add_words(r_d,r_d,t_d,BN_NIST_521_TOP);
return ret; mask = 0-(size_t)bn_sub_words(t_d,r_d,_nist_p_521,BN_NIST_521_TOP);
res = (BN_ULONG *)(((size_t)t_d&~mask) | ((size_t)r_d&mask));
nist_cp_bn(r_d,res,BN_NIST_521_TOP);
r->top = BN_NIST_521_TOP;
bn_correct_top(r);
return 1;
} }