Classification of Near Bent Functions in dimension 7
This page reports the numerical experiments related to the classification of
near bent functions with 7 variables in February 2012, the total running
time was about 4 days.
Let m be a positive odd integer. A Boolean function f from
GF(2)^m into GF(2) is said to be near bent if its Wash
spectrum contains the three values : - 2^(m+1)/2, 0 or +2^(m+1)/2.
The main objective is to classify the Near Bent functions in dimension 7
coming from bent functions in dimension 8 by starting from the classification
of Boolean forms of degree 4 in 7 variables.
A very naive approach works.
For each quartic f in RM(4,7)/RM(2,7) satisfying
the quadratic condition that must satisfy every the bent functions
in dimension 8, we simply check which quadratic form q make f+q
Finaly, we found 88624918554694407235840 near-bent functions in dimension 7 coming from
bent functions, up to an affine term.
- There are
13 classes of near-bent functions of degree less or equal to 3 modulo RM(1,7), the total number of such Boolean functions is 17158683162880 = approx=2^43.96. The fixator distribution is in
- There are
4243469 classes of near-bent functions of degree greater than 3. The order of fixators take 50 distinct values and the total number of such Boolean functions is
88624918537535724072960 =approx= 76.23.
From this data one may probably count the number of bent functions in dimension 8.
Philippe Langevin, Last modification February 2012.