| rsc | b3f6179 | 2004-03-21 14:06:38 +0000 | [diff] [blame] | 1 | #include "os.h" |
| 2 | #include <mp.h> | ||||
| 3 | |||||
| 4 | #define iseven(a) (((a)->p[0] & 1) == 0) | ||||
| 5 | |||||
| 6 | // use extended gcd to find the multiplicative inverse | ||||
| 7 | // res = b**-1 mod m | ||||
| 8 | void | ||||
| 9 | mpinvert(mpint *b, mpint *m, mpint *res) | ||||
| 10 | { | ||||
| 11 | mpint *dc1, *dc2; // don't care | ||||
| 12 | |||||
| 13 | dc1 = mpnew(0); | ||||
| 14 | dc2 = mpnew(0); | ||||
| 15 | mpextendedgcd(b, m, dc1, res, dc2); | ||||
| 16 | if(mpcmp(dc1, mpone) != 0) | ||||
| 17 | abort(); | ||||
| 18 | mpmod(res, m, res); | ||||
| 19 | mpfree(dc1); | ||||
| 20 | mpfree(dc2); | ||||
| 21 | } | ||||