RC4 [was: RE: Passport Passwords Stored in Plaintext]

[Adam Shostack]

On Thu, Oct 11, 2001 at 01:31:36AM -0700, jamesd at echeque.com wrote:
| On 8 Oct 2001, at 11:37, Ray Dillinger wrote:
| > In which case, what you've got isn't RC4 anymore
| 
| You do not understand encryption.
| 
| RC4 is an encryption method, that needs to be part of a
| protocol.  The protocol can be designed correctly or
| incorrectly, but either way it is still a protocol that uses
| RC4.
| 
| In the usual protocols that contain RC4, each session has a
| new transient session key.  The fact that RC4 leaks a small
| amount of information about that session key is unimportant
| in such protocols.
| 
| RC4 is like a brick that can be used to build a house.

I'd say that RC4 is like one of those cool, semi-opaque glass bricks.
Not in the sense that it is weak (you can put quite a bit of load on a 
wall of those) but in the sense that it is different than your typical 
dried-mud sort of brick.  Designing protocols is a hard field, and
there seem to be lots of mistakes made when people use RC4.  Is that
because its a bad cipher?  No, its because people aren't used to
working with it.  Because of that, I tend to look askew at RC4 based
systems.

Adam




-- 
"It is seldom that liberty of any kind is lost all at once."
					               -Hume





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