Register article on using non-randomness of encrypted file content to reduce time needed to decrypt by brute force

[Ian Mason]

On 15 Aug 2013, at 16:00, Igor Mozolevsky wrote:

> On 15 August 2013 11:00, Brian Morrison <bdm at fenrir.org.uk> wrote:
>>
>> Not seen this mentioned anywhere else yet:
>>
>> http://www.theregister.co.uk/2013/08/14/research_shakes_crypto_foundations/
>>
>> Any opinions from those with direct knowledge of such techniques?
>
>
> Isn't the conventional wisdom to compress before encrypting to prevent
> thing like that?

"Conventional wisdom" - yes, actual wisdom, no. The compression layer  
in SSL has been used to attack it (http://breachattack.com/).

The original article is nothing new - it's just a (partial) known  
plaintext attack. Any predictability in the underlying plaintext of a  
cyphertext gives you a handle to attack the cypher with. Most WW2  
cryptanalysis was done around known or likely (partial) plaintexts.  
The moral of the story is, never send anything predictable. If your  
message is predictable mix something genuinely random into it.

>
>
> -- 
> Igor M.
>