Are there...one-way encryption algorithms

David Wagner daw at taverner.cs.berkeley.edu
Thu Nov 20 18:30:53 EST 2003


Anton Stiglic wrote:
>"David Wagner" <daw at taverner.cs.berkeley.edu> wrote:
>> martin f krafft  wrote:
>> >  - Bob encrypts A(M) with key B and sends it to Alice
>> >  - Alice decrypts B(A(M)) with key A, leaving B(M), sends it to Bob
>> >  - Bob decrypts B(M) with key B leaving him with M.
>> >
>> >Are there algorithms for this already? What's the scheme called?
>>
>> It's called Pollig-Hellman.
>
>If I'm not mistaken you are wrong.

You're right.  The above protocol is essentially Shamir's 3-pass
protocol, not Pohlig-Hellman.

Pohlig-Hellman is the encryption scheme A(M) = M^A mod p.  If you
instantiate Krafft's proposal with the Pohlig-Hellman encryption scheme,
you get a working (and secure) instance of Shamir's 3-pass protocol.

Thank you for correcting my error!

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