Replace custom XOR key keyring encryption with gpg

[candide-guevara]

Problem

We use a custom scheme to decrypt/encrypt the backup keyring.
We could do it using gpg, that way the password would be cached and will not be stored in the application memory.

Solution

• Replace custom code in encryption package with shell calls to gpg.
  • Could not find standard lib for gpg

[candide-guevara]

gpg-agent interface is too limited cannot set a custom prompt for each type of password.
Left custom code.