            const BIGNUM *e, BIGNUM *m, BN_CTX *ctx,
                                       int (*bn_mod_exp)(BIGNUM *r,
                                                         const BIGNUM *a,
                                                         const BIGNUM *p,
                                                         const BIGNUM *m,
                                                         BN_CTX *ctx,
                                                         BN_MONT_CTX *m_ctx),
                     