[cryptography] Gregory Perry's follow-up to the FBI OpenBSD / OCF backdoors thread

Harald Hanche-Olsen hanche at math.ntnu.no
Sat Jan 14 08:51:46 EST 2012


[Alfonso De Gregorio <adg at crypto.lo.gy> (2012-01-14 11:38:52 UTC)]

> Back in December 2010, we discussed the OpenBSD IPSec backdoor allegations.
> Two days ago, Cryptome.org published the Gregory Perry's follow-up to
> the this story.
> 
> FBI OpenBSD Backdoors and RSA Cipher Vulnerability
> http://cryptome.org/2012/01/0032.htm

Maybe it's just me, but I find myself unable to make sense of this part:

  [...] one mathematical vulnerability in the RSA encryption algorithm
  related to changing the base numbering system of the resulting RSA
  modulus after a block of plaintext had been encrypted

If "changing the base numbering system" means to express the modulus
in a different base, I utterly fail to see the security implications.
Does it mean something else entirely?

Also, the grammar seems to imply that it is the encryption of a block
of plaintext that results in an RSA modulus. Which seems rather
backward to me.

Not being a crypto expert myself, just a mathematician with a modest
amount of knowledge of matters cryptographical, I don't know if I am
just being obtuse, or if the quoted sentence really is nonsense.

- Harald



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