将GPG与C一起使用？

Question

I am writing a communication program in C and I am looking for the best way to use GnuPG encryption. I am already using symmetric encryption algorithms via the mcrypt library but wish to incorporate some public-key capabilities, preferably using GnuPG if possible. Is there a good library available to accomplish this? Would it be better to try to interact with GPG itself directly via the program to accomplish this? Any insight would be appreciated as I would like to keep this implementation as clean as possible. Thanks.

Answer 1

Unfortunately, GnuPG is designed to be used interactively, and not as an API.

You mention that you are looking to incorporate some public-key capabilities. SSL and TLS are alternatives to GPG which see much more frequent use.

If public-key capabilities in general are what you seek, GnuTLS is an API for use in network based programs that provides exactly what you want. It enjoys a great deal of support, and provides SSL and TLS public-key encryption capabilities.

However, if you are dead set on using GPG, GPGME is a project that exists to wrap an API around GPG. I have not used it and cannot advise on its use, but suspect that it may be somewhat forced.

Answer 2

GPGme is indeed the official API for GPG and is easy to use and well documented (the examples in tests/gpg are very helpful)

Here is an example to encrypt for John Smith:

gpgme_data_t clear_text, encrypted_text;
gpgme_key_t recipients[2] = {NULL, NULL}; 
       /* The array must be NULL-terminated */
...
error = gpgme_op_keylist_start(context, "John Smith", 1);
error = gpgme_op_keylist_next(context, &recipients[0]);
...
error = gpgme_op_encrypt(context, recipients, 
               GPGME_ENCRYPT_ALWAYS_TRUST, 
                           clear_text, encrypted_text);