Encrypting with a subkey?

[Barry A. Warsaw]

I've just started playing with GnuPG.  I wasn't a serious PGP 2.x
user, but I had thing set up so that I could encrypt/decrypt files,
sign email, etc. with my PGP 2.x keys.

So I installed GPG 1.0.1, compiled the RSA extension, and imported my
old PGP 2.x public and private keys.  Then I added a DSA signing key
and an ElGamal encryption key to my existing PGP user id.

The problem is that I don't know how to get GPG to encrypt a file with
the ElGamal key.  I tried setting the default-key value in my
~/.gnupg/options file to the keyid of the ElGamal key, but that
doesn't seem to work.  Whenever I try to encrypt a file, I get the
following warning:

gpg: Warning: using insecure memory!
gpg: RSA keys are deprecated; please consider creating a new key and use this key in the future

It seems to me that I either need to change my primary key from the
old PGP 2.x RSA key, or I need to tell GPG to use a different key for
encrypting.  I've skimmed through the online docs and a bit of the
archives, but if there's a switch or option that needs setting, I must
be missing it.

Any help will be greatly appreciated.  I'm not on this list, so please
CC me with any reply (or I'll watch the archives).

Thanks,
-Barry