Forging key signatures with collisions

[Georgi Guninski]

Forgot the attachment.

On Fri, Jun 22, 2012 at 03:48:07PM +0300, Georgi Guninski wrote:
> Forging key signatures with collisions
> 
> This is a fork of the keyring thread.
> Attached is fake1 key which seemingly appears signed by
> pub   1024D/40976EAF437D05B5 2004-09-12
> uid   Ubuntu Archive Automatic Signing Key <ftpmaster at ubuntu.com>
> 
> which is certainly not the case (good selfsig if the above is not imported)
> 
> Session:
> $gpg --recv-keys 0x437D05B5
> 
> $gpg --import /tmp/fake1 
> gpg: WARNING: digest algorithm MD5 is deprecated
> gpg: please see http://www.gnupg.org/faq/weak-digest-algos.html for more information
> gpg: key 79164387: public key "Ubuntu Archive Automatic Signing Key <ftpmaster at ubuntu.com>" imported #WRONG
> gpg: Total number processed: 1
> gpg:               imported: 1  (RSA: 1)
> $gpg --check-sigs --keyid-f long
> /home/joro2/.gnupg/pubring.gpg
> ------------------------------
> pub   1024D/40976EAF437D05B5 2004-09-12
> uid                          Ubuntu Archive Automatic Signing Key <ftpmaster at ubuntu.com>
> sig!3        40976EAF437D05B5 2004-09-12  Ubuntu Archive Automatic Signing Key <ftpmaster at ubuntu.com>
> sub   2048g/251BEFF479164387 2004-09-12
> sig!         40976EAF437D05B5 2004-09-12  Ubuntu Archive Automatic Signing Key <ftpmaster at ubuntu.com>
> 
> pub   2047R/251BEFF479164387 2012-06-22
> uid                          fake   3 <f at f>
> sig!3        251BEFF479164387 2012-06-22  Ubuntu Archive Automatic Signing Key <ftpmaster at ubuntu.com> #WRONG
> sub   2047R/251BEFF479164387 2012-06-22 
> sig!         251BEFF479164387 2012-06-22  Ubuntu Archive Automatic Signing Key <ftpmaster at ubuntu.com> #WRONG
> 
> 40 signatures not checked due to missing keys
> 
> 
> Stay assured the colliding keysize is completely under control...
> 
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