1. AtomSphere uses CAST5 for encryption. The signing algorithm is based on the algorithm defined in the private key with a hash algorithm of SHA1
2. The PGP libraries are BouncyCastle PGP 1.43
3. The BouncyCastle library utilizes the OpenPGP standard which is the same as GPG. They are interchangeable.
To determine the type of PGP encryption that is being applied to an outbound document view the outbound document after it has been encrypted, the PGP encryption version will be identified immediately after the "-----BEGIN PGP MESSAGE-----" header.
See the example below:
-----BEGIN PGP MESSAGE-----
Version: BCPG v1.45