I want to find at least two (better more of course) private keys within the bitcoin range and leading to the same btc address.
What you are looking for is either one of the following to have occurred:
- A SHA256 collision (2 different inputs that result in the exact same SHA256 outputs)
- A RIPEMD160 collision (2 different inputs that result in the exact same RIPEMD160 outputs)
To my knowledge, there is no record of either having ever occurred (in Bitcoin or otherwise).
Any of these collission will be good as both will lead to the situation where 2 different private keys will result to the same bitcoin address. As ECDSA bitcoin curve guarantees to us that there is only one public key to every private key, so the collision could be only during the public key transormation to the address.
So, you are absolutely right that the collision is in SHA256 or RIPEMD160. But considering the facts that SHA256 transforms 256bit public key (as input) to 256bit output, but RIPEMD160 transforms 256bit to 160bit, so the
highly likely the collision is in
RIPEMD160 function.