Feature Request: support for crypt plugins with only decrypt functionality implemented

[aafemt]

Currently it is impossible to have a crypt plugin that support only decryption because of the method how database signature is checked.

Only working decrypt() function should be enough for read-only access to encrypted databases.

[AlexPeshkoff]

What do you think about adding special function for signature generation to plugin?

[aafemt]

It would make database dependent on plugin implementation. Currently it depends only on used algorithm i.e. any plugin implementing AES encryption can be freely replaced with other. I don't think that such function would be a good idea.

[aafemt]

I would suggest that in the database signature to be stored as encrypted SHA256 hash. In this case its check is a calculation of a new hash, decryption of old hash and comparison of these hashes. SHA256 is chosen because it has size 256 bits i.e. two DES/AES blocks.