-int BN_mod_exp(r,a,p,m,ctx)
-BIGNUM *r;
-BIGNUM *a;
-BIGNUM *p;
-BIGNUM *m;
-BN_CTX *ctx;
+/* this one works - simple but works */
+int BN_exp(BIGNUM *r, BIGNUM *a, BIGNUM *p, BN_CTX *ctx)
+ {
+ int i,bits,ret=0,tos;
+ BIGNUM *v,*rr;
+
+ tos=ctx->tos;
+ v= &(ctx->bn[ctx->tos++]);
+ if ((r == a) || (r == p))
+ rr= &(ctx->bn[ctx->tos++]);
+ else
+ rr=r;
+
+ if (BN_copy(v,a) == NULL) goto err;
+ bits=BN_num_bits(p);
+
+ if (BN_is_odd(p))
+ { if (BN_copy(rr,a) == NULL) goto err; }
+ else { if (!BN_one(rr)) goto err; }
+
+ for (i=1; i<bits; i++)
+ {
+ if (!BN_sqr(v,v,ctx)) goto err;
+ if (BN_is_bit_set(p,i))
+ {
+ if (!BN_mul(rr,rr,v,ctx)) goto err;
+ }
+ }
+ ret=1;
+err:
+ ctx->tos=tos;
+ if (r != rr) BN_copy(r,rr);
+ return(ret);
+ }
+
+int BN_mod_exp(BIGNUM *r, BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
+ BN_CTX *ctx)