[Openswan Users] AES with 256 bits of block size!

[James Muir]

Dariush Zahedmanesh wrote:
> Hi paul
> we changed the config file as you said, but there was an error as follow:
>  esp string error: enc_alg not found, enc_alg="aes_", auth_alg="sha1", 
> modp=""
> 
> we think that the correct syntax is "ike=aes-256 and esp=aes-256", but 
> it is nothing to do with
> the block size. (it only changes the key size not the block size).

The AES standard (i.e. FIPS 197) defines only one blocksize: 128 bits. 
There are 3 different key sizes (128, 192, 256), but only one blocksize. 
  The abbreviations AES-128, AES-192, AES-256 denote different key sizes.

The Rijndael specification does describe how to use different block 
sizes, but this is not yet part of the AES standard.

With a 128-bit block size you can do about 2^64 AES operations before 
you need to worry about birthday attacks.  2^64 is quite a big number. 
Are you certain 2^64 is not large enough for your needs?

-James