public static extern int DH_generate_parameters_ex(IntPtr dh, int prime_len, int generator, bn_gencb_st cb);
public static extern int DSA_generate_parameters_ex(IntPtr dsa, int bits, byte[] seed, int seed_len, out int counter_ret, out IntPtr h_ret, bn_gencb_st callback);
public static extern int RSA_generate_key_ex(IntPtr rsa, int bits, IntPtr e, bn_gencb_st cb);