# Key-recovery attack

A key-recovery attack is an adversary's attempt to recover the cryptographic key of an encryption scheme.[1]:52 Historically, cryptanalysis of block ciphers has focused on key-recovery, but security against these sorts of attacks is a very weak guarantee since it may not be necessary to recover the key to obtain partial information about the message or decrypt message entirely.[1]:52 Modern cryptography uses more robust notions of security. Recently, indistinguishability under adaptive chosen-ciphertext attack (IND-CCA2 security) has become the "golden standard" of security.[2]:566 The most obvious key-recovery attack is the exhaustive key-search attack. But modern ciphers often have a key space of size ${\displaystyle 2^{128}}$ or greater, making such attacks infeasible with current technology.