1 b3f61791 2004-03-21 devnull #include "os.h"
 2 b3f61791 2004-03-21 devnull #include <mp.h>
 3 b3f61791 2004-03-21 devnull 
 4 b3f61791 2004-03-21 devnull #define iseven(a)	(((a)->p[0] & 1) == 0)
 5 b3f61791 2004-03-21 devnull 
 6 cbeb0b26 2006-04-01 devnull /* use extended gcd to find the multiplicative inverse */
 7 cbeb0b26 2006-04-01 devnull /* res = b**-1 mod m */
 8 b3f61791 2004-03-21 devnull void
 9 b3f61791 2004-03-21 devnull mpinvert(mpint *b, mpint *m, mpint *res)
10 b3f61791 2004-03-21 devnull {
11 cbeb0b26 2006-04-01 devnull 	mpint *dc1, *dc2;	/* don't care */
12 b3f61791 2004-03-21 devnull 
13 b3f61791 2004-03-21 devnull 	dc1 = mpnew(0);
14 b3f61791 2004-03-21 devnull 	dc2 = mpnew(0);
15 b3f61791 2004-03-21 devnull 	mpextendedgcd(b, m, dc1, res, dc2);
16 b3f61791 2004-03-21 devnull 	if(mpcmp(dc1, mpone) != 0)
17 b3f61791 2004-03-21 devnull 		abort();
18 b3f61791 2004-03-21 devnull 	mpmod(res, m, res);
19 b3f61791 2004-03-21 devnull 	mpfree(dc1);
20 b3f61791 2004-03-21 devnull 	mpfree(dc2);
21 b3f61791 2004-03-21 devnull }