known-plaintext attacks

[David Shaw]

On Jun 10, 2008, at 10:05 PM, Jan Jansen wrote:

> Hi,
>
> 1. Is the AES-Encryption of a file by gnupg vulnerable to known- 
> plaintext attacks ?

No.

> 2. Does this depend on the lenght of the plaintext ?

No.

> 	2.1 Is a strong Passphrase even safe, if the size of the known  
> plaintext is just 1 Byte or even 10 GB ?

Yes.

> 3. Is it possible for sombody, who does not know the strong  
> Passphrase, to guess reliably, if the encrypted data contains a  
> known file ?

Cannot be answered in the context of this question.  It depends on the  
cipher mode.

> 4. Why or Why not (1.,2.,3 )?

http://en.wikipedia.org/wiki/Advanced_Encryption_Standard#Security

David