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List:       gcrypt-devel
Subject:    Re: no error returns when a wrong key/iv is used for decrypting
From:       Yves Pagani <ypagani () aps ! edu ! pl>
Date:       2011-02-18 8:55:36
Message-ID: 20110218085536.GB3140 () yves ! aps ! edu ! pl
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On Thu, Feb 17, 2011 at 06:28:11PM +0100, Werner Koch wrote:
> On Thu, 17 Feb 2011 15:03, nmav@gnutls.org said:
> 
> > decrypted (you have to define wrong). What you want is to add an
> > authentication layer to that. I.e. add an HMAC to your encrypted data.
> 
> Or do a plaintext detection to see whether you got the right key.
> OpenPGP uses such a feature without introducing the HMAC overhead.  The
> advantage of such a detection feature is that you can check the key
> right after decrypting a few blocks and not only after having decrypted
> a few gigs of ciphertext.  Anyway, it is all a matter of the protocol
> and not of the crypto building blocks.

Hi Nikos, Hi Werner,

Thanks for your quick answers.
I, indeed, though that checking the error code of the cipher_decrypt will allow me to \
warn the user (me in my case :) ) if  a wrong key is given (like gpg does when a \
wrong passphrase is entered). Now, with your explanations I have a clearer \
understanding how to do it properly/working.

By the way, many thanks to all the developpers who done this great library and other \
related tools (gnutls, gnupg and so on).

Have a nice day.
Best regards,
Yves Pagani

-- 
Darth Vader sleeps with a Teddywookie.


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