Subject: Re: NFS file handles are guessable.
To: None <>
From: Angelos D. Keromytis <>
List: tech-security
Date: 03/31/1997 23:11:58
In message <>, "Perry E. Metzger" writ
>A stream cipher can be keyed. If you can't key it, it can't be used as
>a stream cipher, because no one can decrypt what gets encoded with
>it. Taking away the ability to key it (and keying it off of a
>/dev/random) will probably render it exportable.

"keying" a stream cipher can mean two things:
a) set the initial state of the (P)RNG that drives the cipher
b) provide the keystream to XOR the plaintext with, in which case of
course one does not have a stream cipher anymore but just an XOR pad.

I'd say it's hairy trying to define where RNGs stop and stream
ciphers start in regards to legislation. At worst, /dev/random could
be considered a one-time pad generator.

>It is true that a smart person can always re-write the section to do
>keying, but then again, a smart person can get a copy of Applied
>Cryptography and just type in the functioning version from the book
>without having to extensively hack on ours to make it work.

I'll just point out that logic and the law are not always compatible
terms, as the export restriction and other(*) laws have proved twice.

(*) Notably, CDA.