In an article in the french edition of the Scientific American about cryptographic procedures to be used with telecommunications, th= e author tried to explain the Diffie-Helmann Key Exchange algorithm. He introduced a type of funtions called "modular exponentials" (exponentielles modulaires) such as : f : x ÃÂÃÂÃÂÃÂ>Ax (mod p), where A, x and p are integers, and p is prime. The article suggested that two such functions, f and g for example, would commute, so that f[g(x)] = g[(f(x)], enabling two correspo= ndants, each with his, or her, own function, f or g, to compute the same result, knowing a common integer x and the result of the ot= her correspondant's transformation of x, but not the other correspondant's personnal function (Hope no one lost his, or her, breath = on that sentence !) If I have got this right, then I have news for the world around : IT DOES NOT WORK ! Just try with an example ! So, either Mr Diffie, Mr Hellmann and Mr Merkle should change the batteries of their pocket calculators, or there is something I mis= sed. I am enclined to think the second alternative is a better chance, but if nobody helps me out of this one in a jiffy, I will publish = the first. Thanks in advance.