Re: Key length security (calculations!)

solman@mit.edu writes (quoting someone else initially):

>> You mention Shamir, etc.  However I would point out that even if any of the
>> original RSA mathematicians found a better factoring algorithm, they'd be 
>more
>> than likely to keep it under lock and key.  The obvious reason is that their
>> money supply depends on such an algorithm being suppressed.

>What about Shamir's triple pass key exchange protocol (explained briefly
>below). Its the perfect key exchange algorithm. It obsoletes Public key
>systems entirely as long as you only need to exchange keys and not
>authenticate. I'd say that is pretty decent evidence that he does still
>do things to help the field when it might hurt RSADSI. (although I wouldn't
>say the same thing about all of them)

I suspect this protocol is covered by the Diffie-Hellman patent, which is
quite broad, covering many sorts of key exchanges.  Diffie-Hellman is now
owned by PKP, the sister company to RSA.  If so, Shamir has not undercut his
own financial interests by this work.  (Also, this does not obsolete PK
since it requires several exchanges before communication can occur, making
it inappropriate for high-latency communications, such as for most email.)

Hal

[I describe the shamir triple pass key exchange protocol]

> I suspect this protocol is covered by the Diffie-Hellman patent, which is
> quite broad, covering many sorts of key exchanges.  Diffie-Hellman is now
> owned by PKP, the sister company to RSA.  If so, Shamir has not undercut his
> own financial interests by this work.  (Also, this does not obsolete PK
> since it requires several exchanges before communication can occur, making
> it inappropriate for high-latency communications, such as for most email.)

Can anybody verify this? I thought that DH only applied to public key systems.
Surely the idea of exchanging keys can't be patented. You have to patent the
process and I though DH just took care of the public key symetric key exchange 
process.

JWS

JWS writes:

>[I describe the shamir triple pass key exchange protocol]

>> I suspect this protocol is covered by the Diffie-Hellman patent, which is
>> quite broad, covering many sorts of key exchanges.  Diffie-Hellman is now
>> owned by PKP, the sister company to RSA.  If so, Shamir has not undercut his
>> own financial interests by this work.  (Also, this does not obsolete PK
>> since it requires several exchanges before communication can occur, making
>> it inappropriate for high-latency communications, such as for most email.)

>Can anybody verify this? I thought that DH only applied to public key systems.
>Surely the idea of exchanging keys can't be patented. You have to patent the
>process and I though DH just took care of the public key symetric key exchange 
>process.

As I recall, the patent is very general.  A sends a message to B, B sends
one back to A; this goes on for a while, then both sides feed their messages
into a black box and, presto, out pops a suitable encryption key which is the
same for both sides, but is such that no eavesdropper could feasibly produce
the key.  It's been a long time since I looked at it, though.  I would welcome
some verification.

(I should also add that my comment about Shamir not undercutting his own
financial interests was apparently incorrect if he has actually sold out his
interest in RSA as reported.)

Hal