Decisional composite residuosity assumption
The decisional composite residuosity assumption (DCRA) is a mathematical assumption used in cryptography. In particular, the assumption is used in the proof of the Paillier cryptosystem.
Informally the DCRA states that given a composite n and an integer z, it is hard to decide whether z is a n-residue modulo n2 or not, i.e., whether there exists y such that
...
Wikipedia