[Mageia-dev] PGP keys and package signing

[Pascal Terjan]

On Tue, Feb 1, 2011 at 00:35, Dick Gevers <dvgevers at xs4all.nl> wrote:
> On Tue, 01 Feb 2011 00:15:36 +0100, Michael Scherer wrote about Re:
> [Mageia-dev] PGP keys and package signing:
>
>>Le lundi 31 janvier 2011 à 21:49 +0000, Dick Gevers a écrit :
>>> On Mon, 31 Jan 2011 17:18:25 +0100, Michael Scherer wrote about Re:
>>> [Mageia-dev] PGP keys and package signing:
>>>
>>> >The problem is not leaking the key, it is about cryptographic attacks
>>> >about older keys.
>>> >
>>> >If in 10 years, there is some technology that allows people to get our
>>> >private key by bruteforce on the public one
>>>
>>> You can never ever obtain the private key from the public one, that is
>>> impossible. It can only be compromised if someone looses the private key
>>> plus the password is cracked.
>>
>>Some secure systems have been seen compromised ( like
>>http://www.win.tue.nl/hashclash/rogue-ca/, who explain how the whole SSL
>>business was compromised 2 years ago, or see the GSM being cracked at
>>this year 27C3 ).
>>
>>And Debian also got ride of older vulnerable gpg keys ( see
>>http://lists.debian.org/debian-devel-announce/2010/04/msg00018.html and
>>http://lists.debian.org/debian-devel-announce/2010/09/msg00003.html ),
>>so I would not be so optimistic about the "never".
>>
>>Technically, MD5 should not have been reversible, but see how easy it is
>>using a rainbow table. Granted, that's a 20 year protocol, but that's
>>still widely used in lots of software.
>
> Sorry, but I am not convinced: the gpg key we are talking about consists of
> 2 parts: the private key is separate from the public key, or signing key.
> The signing key is a separate or subkey and does not contain any part of the
> private key. So you can throw any amount of computing power at it, but
> there is nothing inside the public key that will enable the rebuilding of
> the private key from it.

Encrypt stuff with the public one, try to decrypt it with the 2^4096
(or whatever) possible private keys.