# cyclotomy

**Cyclotomy** is a name used for a method of primality
proving begun around 1981 when H. W. Lenstra combined the
Jacobi Sum methods of Adleman, Rumely, and Pomerance
(the APR-test), with the classical primality tests. It was first implemented by W. Bosma and M. van der Hulst in 1989. Currently cyclotomy (along with other variants of the APR test) and ECPP are the standard methods for general primality proving of integers with 1000+ digits.

The classical tests all require auxilary factoring. In particular they require that we be able to factor *n*^{2}-1 enough that the factored part is about the cube root of *n*. This is easy for primes like the Mersenne primes, Woodall primes, Fermat primes,... but not for general primes. Cyclotomy extends these classic test to all the factors of any of the numbers

n-1 with^{k}k< (logn)^{log log log n}.

(In this sense Cyclotomy is neoclassical.)
The product of these factors must be at least *n*^{1/3} for the test to work.

It is always possible to find the necessary factors. In fact it has been shown that there is always an integer
*k* with

k< (logn)^{log log log n}

for which
the factors *q* dividing *n ^{k}*-1 with

*q*-1 dividing

*k*, have a product at least the size of the square root of

*n*. Usually

*k*is around 100,000,000 for numbers

*n*with about 3,000 digits.

**See Also:** ECPP

**Related pages** (outside of this work)