twofish keysize

[Werner Koch]

On Mon, 19 Apr 2004 00:19:58 +0200, Malte Gell said:

> Maybe he expects a performance advantage when using 128 bit keys instead 
> of 256 bit. By the way, are there estimations how much slower a 256 bit 
> Twofish key is? I guess one will only notice it whith huge amount of 

here are encrypt/decrypt result from libgcrypt.

           ECB             CBC             CFB             CTR             
           --------------- --------------- --------------- ----------------
3DES         140ms   150ms   170ms   190ms   150ms   160ms   180ms   180ms 
CAST5         50ms    50ms    70ms    80ms    60ms    60ms    90ms    80ms 
BLOWFISH      90ms   100ms   110ms   120ms   110ms   110ms   130ms   130ms 
AES           40ms    40ms    50ms    60ms    40ms    50ms    80ms    80ms 
AES192        40ms    40ms    60ms    60ms    50ms    50ms    80ms    80ms 
AES256        40ms    50ms    60ms    70ms    50ms    60ms    90ms    80ms 
TWOFISH       50ms    50ms    60ms    60ms    60ms    60ms   100ms   100ms 
TWOFISH128    50ms    50ms    60ms    60ms    60ms    60ms   100ms   100ms

As you can see, there is no difference between twofish (256 bit) and
twofish 128.

The disadvantage of a 256 bit key is that is requires double as much
entropy to create a session key.


  Werner