This module interfaces to some of the OpenSSL ciphers without using EVP (see OpenSSL.EVP.Cipher). The EVP ciphers are easier to use, however, in some cases you cannot do without using the OpenSSL fuctions directly.
One of these cases (and the motivating example for this module) is that the EVP CBC functions try to encode the length of the input string in the output (thus hiding the fact that the cipher is, in fact, block based and needs padding). This means that the EVP CBC functions cannot, in some cases, interface with other users which don't use that system (like SSH).
For CTR mode, this must always be Encrypt
Key: 128, 192 or 256 bits long
IV: 16 bytes long
|-> IO AESCtx|
Construct a new context which holds the key schedule and IV.
Encrypt some number of blocks using CBC. This is an IO function because the context is destructivly updated.