Encrypting / decrypting without importing keys?

[Eric B.]

Hi,

I'm new to GnuPG and was wondering if it was possible to encrypt and/or
decrypt without needing to first import the keys into gpg.  I'm looking to
use gpg to encrypt data from a web page, where the user specifies the public
key to encrypt data, and then eventually a private key to decrypt it.

Additionally, is there anyway I can specify the keys to use as coming from
standard in or standard out instead of being file based?

Thanks!

Eric