1 /* mpi-pow.c  -  MPI functions
18  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
24  *	 to avoid revealing of sensitive data due to paging etc.
31 #include "mpi-internal.h"
52 	int rc = -ENOMEM;  in mpi_powm()
54 	esize = exp->nlimbs;  in mpi_powm()
55 	msize = mod->nlimbs;  in mpi_powm()
57 	msign = mod->sign;  in mpi_powm()
59 	rp = res->d;  in mpi_powm()
60 	ep = exp->d;  in mpi_powm()
63 		return -EINVAL;  in mpi_powm()
68 		res->nlimbs = (msize == 1 && mod->d[0] == 1) ? 0 : 1;  in mpi_powm()
69 		if (res->nlimbs) {  in mpi_powm()
72 			rp = res->d;  in mpi_powm()
75 		res->sign = 0;  in mpi_powm()
86 	mod_shift_cnt = count_leading_zeros(mod->d[msize - 1]);  in mpi_powm()
88 		mpihelp_lshift(mp, mod->d, msize, mod_shift_cnt);  in mpi_powm()
90 		MPN_COPY(mp, mod->d, msize);  in mpi_powm()
92 	bsize = base->nlimbs;  in mpi_powm()
93 	bsign = base->sign;  in mpi_powm()
96 		 * (The quotient is (bsize - msize + 1) limbs.)  */  in mpi_powm()
100 		MPN_COPY(bp, base->d, bsize);  in mpi_powm()
109 		bp = base->d;  in mpi_powm()
112 		res->nlimbs = 0;  in mpi_powm()
113 		res->sign = 0;  in mpi_powm()
117 	if (res->alloced < size) {  in mpi_powm()
129 			rp = res->d;  in mpi_powm()
172 		negative_result = (ep[0] & 1) && base->sign;  in mpi_powm()
174 		i = esize - 1;  in mpi_powm()
178 		c = BITS_PER_MPI_LIMB - 1 - c;  in mpi_powm()
186 		 * by RP (==RES->d), and with 50% probability in the area originally  in mpi_powm()
192 				mpi_ptr_t tp;  in mpi_powm()  local
223 				tp = rp;  in mpi_powm()
225 				xp = tp;  in mpi_powm()
251 					tp = rp;  in mpi_powm()
253 					xp = tp;  in mpi_powm()
257 				c--;  in mpi_powm()
261 			i--;  in mpi_powm()
269 		 * steps.  Adjust the result by reducing it with the original MOD.  in mpi_powm()
271 		 * Also make sure the result is put in RES->d (where it already  in mpi_powm()
276 			    mpihelp_lshift(res->d, rp, rsize, mod_shift_cnt);  in mpi_powm()
277 			rp = res->d;  in mpi_powm()
283 			MPN_COPY(res->d, rp, rsize);  in mpi_powm()
284 			rp = res->d;  in mpi_powm()
306 	res->nlimbs = rsize;  in mpi_powm()
307 	res->sign = rsign;  in mpi_powm()