Symmetric cipher padding?

Brad Hards bradh at
Mon Mar 21 10:27:38 CET 2005

On Mon, 21 Mar 2005 03:50 am, Moritz Schulte wrote:
> I am not entirely sure about your question, but I assume you are
> asking what padding mechanisms Libgcrypt provides in respect to
> symmetric block ciphers.  The answer is: none; you have to do your
> padding yourself.  Note that if you are dealing with data, whose size
> is larger than a single block size, you can use CTS (cipher text
> stealing) instead of padding.
Hmm, OK. I guess I have three more questions then :-) If there is a -user list 
I should be using, please let me know...

1. I've been working on the assumption that if I pass more than block size 
bytes to gcry_cipher_encrypt(), then libgcrypt will buffer the residual 
bytes. Is this the case, or am I meant to be doing the buffering myself?

2. Is there  anything that I can use to help with the padding? For example, 
does libgcrypt keep track of how many bytes have been encrypted already?

3. Is there any special support for CTS? (or, can I have a hint please :)

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