Public-key encrypt/sign: providing Passphrase programmatically via Callbacks

[Vijay K.N.]

Hi,
 
I am using GPG to sign/encrypt messages using
DSA/Elgamel 2048-bit keys. I would like to pass the
pass-phrase for secret keys programmatically - so that
I don't get a pop-up for every message that needs to
be signed. 
 
I tried using Callbacks for providing the passphrase -
but apparently the callbacks are not getting invoked.
Referring to the GPG documentation seemed to suggest
that support for providing passphrase via callbacks is
limited to certain algorithms. 
 
Appreciate if someone can clarify whether providing
passphrase programmatically is supported for the above
GPG public-key encryption/signature operation, in
GPG1.4.2 and if so, how it can be done.
 
thanks
Vijay

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