[Mageia-dev] PGP keys and package signing

Tue Feb 1 11:47:46 CET 2011

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.
+