[difficulty: 3][protection: ECDSA]
The moderator comments revealed that it did some type of ECC, so I had to try it in continuation of my elliptic journey. Fortunately, it implements ECDSA just like WiteG #10. But in this crackme, you have to actually forge a signature for a message generated from your user name (actually it is bignum(sha1(user)) just like the previous crackme!).
Of course ECDSA would be useless if forgery were possible without knowing the private key. I enlisted Mr. Haandi's ECDLP Solver v0.2a to find the discrete log (just the scalar k so that k * G = public key). The crackme uses extremely small parameters for its curve, so the solver finished in about 1/5th of a second.
From there it's just calculation...