Algebraic Cryptography Center

Let be the group of braids on strands and its standard generators. Define two subgroups and of as follows: and Clearly, and commute elementwise. The Ko-Lee protocol [1] is the following sequence of operations:

(0) One of the parties (say, Alice) publishes a random element (the ``base" word).

(1) Alice chooses a word as a product of generators of and their inverses. The word is Alice's private key.

(2) Bob chooses a word as a product of generators of and their inverses. The word is Bob's private key.

(3) Alice sends a normal form of the element to Bob and Bob sends a normal form of the element to Alice.

(4) Alice computes a normal form of and Bob computes a normal form of Since in , the normal forms of and coincide. Thus Alice and Bob have the same normal form called their shared secret key.

Under construction ...

Under construction ...

Under construction ...

1. K.H.Ko, S.J.Lee, J.H.Han, J.Kang, C.Park. New public-key Cryptosystem using braid groups. CRYPTO'2000, LNCS 1880, pp.166-183, 2000.
2. R.Gennaro, D.Micciancio. Cryptoanalysis of a pseudorandom generator based on braid groups. Advances in Cryptology, EUROCRYPT 2002, LNCS 2332, pp.1-13, 2002.