Here's the deal:
I have a Buffer of data structured like this:
[39 bytes of header] + [body] + [padding] (calculated by me).
If I save it to a file, I can actually recognize the structure, and everything seems fine.
Then, I have to DES-CBC encrypt this buffer, and what I do is
a) Instantiate the DES wrapper, which has a key, and calculates a new IV (autoPadding: false on the Cipher object it creates, too)
b) Pass the buffer to the DES wrapper
c) The buffer then gets encrypted as follows:
(data is the buffer, en is the Cipher object)
var buf1 = en.update(data);
When I output buf1 on a file (and then, in my case, on a socket) and retrieve it's bytes, then decrypt it I obtain the following structure:
[header][body]
But when I output data on a file and retrieve it's bytes, I get the starting structure.
I know I should also append en.final() to buf1, but in my case I don't need those values, also with autoPadding being false it would just throw an error.
The API provides you with a contract. One of the properties of the contract is that you need to call Cipher#final([output_encoding]) when you finished encrypting. Even if the padding doesn't need to be handled by the Cipher instance, the code is written for re-usability and therefore expects to be used in the same way regardless of padding options.