Key-recovery attack

<p>A key-recovery attack is an adversary's attempt to recover the <a href="/facts/Key_(cryptography)/5W5PAmT4">cryptographic key</a> of an encryption scheme. Normally this means that the attacker has a pair, or more than one pair, of <a href="/facts/Plaintext/tWnBDCgE">plaintext</a> message and the corresponding <a href="/facts/Ciphertext/luNTs4sY">ciphertext</a>.: 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.: 52  Modern cryptography uses more robust notions of security. Recently, <a href="/facts/Ciphertext_indistinguishability/2oumAzNt">indistinguishability under adaptive chosen-ciphertext attack</a> (IND-CCA2 security) has become the "golden standard" of security.: 566  The most obvious key-recovery attack is the <a href="/facts/Exhaustive_key_search/TXl8pkfb">exhaustive key-search</a> attack. But modern ciphers often have a key space of size 
  
    
      
        
          2
          
            128
          
        
      
    
    {\displaystyle 2^{128}}
  
 or greater, making such attacks infeasible with current technology.
</p>

Key-recovery attack open-in-new

Key-recovery attack