How to invert the ExponentiateBase function

[Pasilda]

Hi there.

Consider this code:
=====
Integer x;
DL_PrivateKey_EC<ECP> priv;
a = priv.AccessAbstractGroupParameters().ExponentiateBase(x);
=====

Is it possible to find out the value of X if I know the value of A
and I have the private key?

It seems to me that a logarithm should do the job, but there seems not
to be one in Crypto++.



The code is equivallent to this:
=====
Integer x;
DL_PrivateKey_EC<ECP> priv;
DL_GroupParameters<ECPPoint> &params = priv.AccessAbstractGroupParameters();
const DL_FixedBasePrecomputation<ECPPoint> &b = params.GetBasePrecomputation();
const DL_GroupPrecomputation<ECPPoint> &g = params.GetGroupPrecomputation();

ECPPoint a;
a = b.Exponentiate(g, x);
=====

Regards.