Using pgcrypto with AES-256 bits?

Hello.

I tried the pgcrypto contrib module with the AES default encryption. It
works pretty nice, but I understand that it's using 128 bit key strength. Is
there any built-in support for the 256 bit key strength? Or it should be
used via external libraries?

AFAIK, the support of mhash and mcrypt was dropped from the recent version
of the module, so the AES 256 functionality can be only provided by OpenSSL?

Thank you.

Stas.