Make specification of parameters for encryption/decryption possible

Encryption tasks (and their decryption counterparts) now use a fixed algorithm (AES) with a fixed key length (256 bits) and mode (CFB). It would be convenient to provide means to specify, and use, other parametrizations of encryption/decryption tasks.

A way to provide encryption/decryption parametrization would be through one or more new arguments. As a rule, algorithms take several parameters (typically algorithm, key length and mode), but which ones apply or are necessary depends on the exact algorithm (with some - block algs. - having modes, some not, some variable key or even block length, etc). So it may be better to include all of them as a single parameter. In this case, adequate information about their format (e.g.: 256-bit AES in CFB mode could be specified as AES-256-CFB, in that order) would have to be provided. Also, independent of the number of arguments that are used to specify the parameters, a way to list valid parameter sets would have to be available.

Up until now there was only one possible parametrization, so only one type of encryption was possible. Although decryption could very well be parametrized in exactly the same way as encryption, it would make more sense to use the meta data that was created as part of the encryption process to deal with decryption.

The modification would be simple in the current version, but any solution would have to have into account possible changes in the underlying cryptographic engine.