|
282
|
1 #include <tommath.h> |
|
|
2 #ifdef BN_MP_REDUCE_IS_2K_C |
|
|
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis |
|
|
4 * |
|
|
5 * LibTomMath is a library that provides multiple-precision |
|
|
6 * integer arithmetic as well as number theoretic functionality. |
|
|
7 * |
|
|
8 * The library was designed directly after the MPI library by |
|
|
9 * Michael Fromberger but has been written from scratch with |
|
|
10 * additional optimizations in place. |
|
|
11 * |
|
|
12 * The library is free for all purposes without any express |
|
|
13 * guarantee it works. |
|
|
14 * |
|
|
15 * Tom St Denis, [email protected], http://math.libtomcrypt.org |
|
|
16 */ |
|
|
17 |
|
|
18 /* determines if mp_reduce_2k can be used */ |
|
|
19 int mp_reduce_is_2k(mp_int *a) |
|
|
20 { |
|
|
21 int ix, iy, iw; |
|
|
22 mp_digit iz; |
|
|
23 |
|
|
24 if (a->used == 0) { |
|
|
25 return MP_NO; |
|
|
26 } else if (a->used == 1) { |
|
|
27 return MP_YES; |
|
|
28 } else if (a->used > 1) { |
|
|
29 iy = mp_count_bits(a); |
|
|
30 iz = 1; |
|
|
31 iw = 1; |
|
|
32 |
|
|
33 /* Test every bit from the second digit up, must be 1 */ |
|
|
34 for (ix = DIGIT_BIT; ix < iy; ix++) { |
|
|
35 if ((a->dp[iw] & iz) == 0) { |
|
|
36 return MP_NO; |
|
|
37 } |
|
|
38 iz <<= 1; |
|
|
39 if (iz > (mp_digit)MP_MASK) { |
|
|
40 ++iw; |
|
|
41 iz = 1; |
|
|
42 } |
|
|
43 } |
|
|
44 } |
|
|
45 return MP_YES; |
|
|
46 } |
|
|
47 |
|
|
48 #endif |
