As you said, encryption is not the same as hashing as you need to be able to decrypt in the case of encryption. This would have to be custom code. You could have a look at the Exchange module in the Appstore where there is a bit of code for encrypting and decrypting the user's password for the Exchange server as well (I used AES there, though I believe it was 128 bit).
Obviously you also need to store an encryption key somewhere. I used a constant for this so it can be adjusted for production.