Large Primes

[Brian Gladman]

From: "Owen Lewis" <oml@sysrx.uk.com>
To: <ukcrypto@chiark.greenend.org.uk>
Sent: Friday, August 16, 2002 2:36 PM
Subject: RE: Large Primes

[snip]
> As such systems are presently arranged, at best they offer their users no
> more than the protection of a single cipher, the invulnerability of which
> cannot be certain. Moreover, they offer two different ciphers as targets
> with a failure of either, taken alone, being sufficient to destroy the
> system's security. If, for the sake of simple argument, we say that the
> probability (P) of a successful attack on either type of cipher is about
the
> same then, by arranging the work of the two ciphers in the current
fashion,
> the engineer increases the probability of a successful attack to P/2 where
P
> is less than unity.

   ... successful attack to 2P ...   :-)

   Brian