Name  Encryption Brute Forcing 
Summary  An attacker, armed with the cipher text and the encryption algorithm used, performs an exhaustive (brute force) search on the key space to determine the key that decrypts the cipher text to obtain the plaintext. 
Prerequisites  Ciphertext is known.
Encryption algorithm and key size are known. 
Solutions  Use commonly accepted algorithms and recommended key sizes. The key size used will depend on how important it is to keep the data confidential and for how long.
In theory a brute force attack performing an exhaustive key space search will always succeed, so the goal is to have computational security. Moore's law needs to be taken into account that suggests that computing resources double every eighteen months. 
Related Weaknesses 
CWE ID  Description 
CWE326  Inadequate Encryption Strength 
CWE327  Use of a Broken or Risky Cryptographic Algorithm 
CWE693  Protection Mechanism Failure 
CWE719  
