gpgme_key_t or gpgme_op_export_keys keydata to gcry_sexp_t

[Mike Inman]

Hi,

I'm trying to work with gpgme to manage public/private key pairs on a
keyring, but also use these keys with libgcrypt for signing, verifying
signatures, etc. without interacting with gpg or the keyring...

I've found and used the functions like:
https://www.gnupg.org/documentation/manuals/gpgme/Listing-Keys.html#Listing-Keys
and
https://www.gnupg.org/documentation/manuals/gpgme/Exporting-Keys.html#Exporting-Keys,
and I see in libgcrypt what it's expecting:
https://www.gnupg.org/documentation/manuals/gcrypt/Cryptographic-Functions.html
but I don't feel like I have enough information to make a bridge between
the two.

For instance, when I create an ECDSA key with the brainpoolP256r1 curve,
then I gpgme_op_export() that key in GPGME_EXPORT_MODE_MINIMAL mode, I get
413 bytes in the keydata - is the X9.62 encoded key in there anywhere?  If
so, how can I reliably get it out?

Thanks,
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