class type cipher =object
..end
method name : string
method mode : string
method key_lengths : (int * int) list
min,max
. If there is a recommended
key length, this is the first.method iv_lengths : (int * int) list
min,max
. If there is a recommended
iv length, this is the first.method block_constraint : int
method supports_aead : bool
method create : string -> padding -> cipher_ctx
create c p key
: create a new cipher context for key
. If not set,
the initialization vector is assumed to be zero, and the header the
empty string.
The cipher context can be used for either encrypting or decrypting a
single message.