bytes=(bits+7)/8;
bit=(bits-1)%8;
- mask=0xff<<bit;
+ mask=0xff<<(bit+1);
buf=(unsigned char *)OPENSSL_malloc(bytes);
if (buf == NULL)
}
#endif
- if (top)
+ if (top != -1)
{
- if (bit == 0)
+ if (top)
{
- buf[0]=1;
- buf[1]|=0x80;
+ if (bit == 0)
+ {
+ buf[0]=1;
+ buf[1]|=0x80;
+ }
+ else
+ {
+ buf[0]|=(3<<(bit-1));
+ }
}
else
{
- buf[0]|=(3<<(bit-1));
- buf[0]&= ~(mask<<1);
+ buf[0]|=(1<<bit);
}
}
- else
- {
- buf[0]|=(1<<bit);
- buf[0]&= ~(mask<<1);
- }
- if (bottom) /* set bottom bits to whatever odd is */
+ buf[0] &= ~mask;
+ if (bottom) /* set bottom bit if requested */
buf[bytes-1]|=1;
if (!BN_bin2bn(buf,bytes,rnd)) goto err;
ret=1;
return bnrand(2, rnd, bits, top, bottom);
}
#endif
+
+
+/* random number r: 0 <= r < range */
+int BN_rand_range(BIGNUM *r, BIGNUM *range)
+ {
+ int n;
+
+ if (range->neg || BN_is_zero(range))
+ {
+ BNerr(BN_F_BN_RAND_RANGE, BN_R_INVALID_RANGE);
+ return 0;
+ }
+
+ n = BN_num_bits(range); /* n > 0 */
+
+ if (n == 1)
+ {
+ if (!BN_zero(r)) return 0;
+ }
+ else if (BN_is_bit_set(range, n - 2))
+ {
+ do
+ {
+ /* range = 11..._2, so each iteration succeeds with probability >= .75 */
+ if (!BN_rand(r, n, -1, 0)) return 0;
+ }
+ while (BN_cmp(r, range) >= 0);
+ }
+ else
+ {
+ /* range = 10..._2,
+ * so 3*range (= 11..._2) is exactly one bit longer than range */
+ do
+ {
+ if (!BN_rand(r, n + 1, -1, 0)) return 0;
+ /* If r < 3*range, use r := r MOD range
+ * (which is either r, r - range, or r - 2*range).
+ * Otherwise, iterate once more.
+ * Since 3*range = 11..._2, each iteration succeeds with
+ * probability >= .75. */
+ if (BN_cmp(r ,range) >= 0)
+ {
+ if (!BN_sub(r, r, range)) return 0;
+ if (BN_cmp(r, range) >= 0)
+ if (!BN_sub(r, r, range)) return 0;
+ }
+ }
+ while (BN_cmp(r, range) >= 0);
+ }
+
+ return 1;
+ }