Alternatively have a look at the program.

## On the counting function of the range of the Carmichael $\lambda$-function

The Carmichael $\lambda$-function associates to $n$ the exponent $\lambda(n)$ of the multiplicative group modulo $n$. In my talk, I will describe the main ideas behind the proof that the counting function $\#\{\lambda(n)\le x\}$ of the range of the Carmichael function $\lambda(n)$ below $x$ is $x/(\log x)^{\eta+o(1)}$ as $x\to\infty$, where $\eta=1-(1+\log\log 2)/\log 2=0.08607\ldots$ is the ErdÅ‘s-Tenebaum-Ford constant. The proof uses sieve methods. This is joint work with Kevin Ford and Carl Pomerance.

## On the period of some pseudo-random number generators and "number-theoretical turbulence"

Given coprime integers b and n, let ord(b,n) be the

multiplicative order of b modulo n. The length of the periods of some

popular pseudorandom number generators (e.g., the linear congruential

generator, and the Blum-Blum-Shub generator) turns out to be related

to ord(b,n) for appropriately chosen b and n. We will investigate

some conclusions by V.I. Arnold (based on numerics by F. Aicardy as

well as analogies with the physical principle of turbulence) on the

average of ord(b,n), as n ranges over integers. We will also give

## A refinement of the abc conjecture

We shall discuss joint work with Robert and Tenenbaum on a

proposed refinement of the well known abc conjecture.

## Complex multiplication in cryptography

Algorithms going under the name `complex multiplication' typically have a run time that is exponential in the size of the input data. We will show that nevertheless such algorithms may sometimes be profitably used in cryptographic settings.