|
2
|
1 /* LibTomMath, multiple-precision integer library -- Tom St Denis |
|
|
2 * |
|
|
3 * LibTomMath is a library that provides multiple-precision |
|
|
4 * integer arithmetic as well as number theoretic functionality. |
|
|
5 * |
|
|
6 * The library was designed directly after the MPI library by |
|
|
7 * Michael Fromberger but has been written from scratch with |
|
|
8 * additional optimizations in place. |
|
|
9 * |
|
|
10 * The library is free for all purposes without any express |
|
|
11 * guarantee it works. |
|
|
12 * |
|
|
13 * Tom St Denis, [email protected], http://math.libtomcrypt.org |
|
|
14 */ |
|
|
15 #include <tommath.h> |
|
|
16 |
|
|
17 /* makes a pseudo-random int of a given size */ |
|
|
18 int |
|
|
19 mp_rand (mp_int * a, int digits) |
|
|
20 { |
|
|
21 int res; |
|
|
22 mp_digit d; |
|
|
23 |
|
|
24 mp_zero (a); |
|
|
25 if (digits <= 0) { |
|
|
26 return MP_OKAY; |
|
|
27 } |
|
|
28 |
|
|
29 /* first place a random non-zero digit */ |
|
|
30 do { |
|
|
31 d = ((mp_digit) abs (rand ())); |
|
|
32 } while (d == 0); |
|
|
33 |
|
|
34 if ((res = mp_add_d (a, d, a)) != MP_OKAY) { |
|
|
35 return res; |
|
|
36 } |
|
|
37 |
|
|
38 while (digits-- > 0) { |
|
|
39 if ((res = mp_lshd (a, 1)) != MP_OKAY) { |
|
|
40 return res; |
|
|
41 } |
|
|
42 |
|
|
43 if ((res = mp_add_d (a, ((mp_digit) abs (rand ())), a)) != MP_OKAY) { |
|
|
44 return res; |
|
|
45 } |
|
|
46 } |
|
|
47 |
|
|
48 return MP_OKAY; |
|
|
49 } |
