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obfs3 currently uses Python's built-in pow() for modular exponentiation. The computation can be made less expensive by using GMPY. Apart from making UniformDH computationally less expensive, it creates less of a timing signature. That's relevant for ScrambleSuit as its two authentication methods should be indistinguishable.

I have patches for this improvement in my user repository in the branch use_gmp: https://gitweb.torproject.org/user/phw/obfsproxy.git

Note that the patch requires the module gmpy which is not part of Python's standard library. Debian knows the package as python-gmpy.