  The paper discusses the Andrews-Curtis graph of a normal subgroup N in a
group G. The vertices of the graph are k-tuples of elements in N which generate
N as a normal subgroup; two vertices are connected if one them can be obtained
from another by certain elementary transformations. This object appears
naturally in the theory of black box finite groups and in the Andrews-Curtis
conjecture in algebraic topology.
  We suggest an approach to the Andrews-Curtis conjecture based on the study of
Andrews-Curtis graphs of finite groups, discuss properties of Andrews-Curtis
graphs of some classes of finite groups and results of computer experiments
with generation of random elements of finite groups by random walks on their
Andrews-Curtis graphs.
