Re: [TLS] Upload of draft-pironti-tls-length-hiding-00

[Nikos Mavrogiannopoulos <[e-mail]>]

On 02/12/2013 07:04 AM, Martin Rex wrote:

> Alfredo Pironti wrote:
>> I uploaded a draft that explains how to correctly use extra padding in
>> TLS to effectively hide the plaintext length. The draft proposes an
>> extension where length-hiding padding can be used with any cipher.
> Since TLS implementations will likely need to support interop
> for the original ciphersuites and GenericBlockCipher, GenericStreamCipher
> and GenericAEADCipher for many years to come, I would personally prefer
> to keep the PDU changes to a minimum.
> Is there any specific benefit or necessity for the padding to be inserted
> before the plaintext, rather than directly trailing the plaintext?


The main reason is that it is much easier to remove this padding using
the current TLS parsing methods (i.e. two bytes the length, and data
follow).

The alternative would be to put the two length bytes at the end and the
padding data would be just before that. That would require a custom
parser for that packet that isn't used anywhere in TLS.

regards,
Nikos