CryptoNote deals with attacks by employing ring signatures and key images. If a rogue user creates more than one ring signature using the same private key, these signatures will be linked together which indicates a double-spending attempt. In order to provide linkability, CryptoNote introduced a special key image which is created by a user while signing a transaction. It is the value of a cryptographic one-way function of the secret key, or in other words it is actually an image of this key. It is computationally infeasible to find a collision (two different private keys, which have the same image). In case of double-spending attempt the system immediately reject any new ring signature with a duplicate key image. It won’t be able to pinpoint a misbehaving user, but it does prevent any double-spending attempts. There was never a documented occasion of a double-spending attack in the history of Bytecoin (BCN) or any other CryptoNote -based coin.