Project 11 has prepared sets of ECC keys from 1 to 25 bits of security. Participants will need to target these key lengths and demonstrate that their methods can crack the provided x-bit key.
Where I can find the exact keys? Because I think it may be a good exercise, to first break all of them classically, and just see, how they generated these small elliptic curves. Breaking ECDSA is one thing, but discovering the exact way of how secp160k1, secp192k1, secp224k1, and secp256k1 was made, is also a challenge in itself (specifically: how their generators were picked).