Cryptography for Network and Information Security
Cryptography for Network and Information Security |
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Key length is only one factor in the strength of both symmetric key and public key cryptography algorithms. The longer that a secret key or private key is used, the more susceptible it is to attack. The longer a key is used, the greater the amount of information that is encrypted with the key. In addition, a longer key lifetime also gives attackers more time to exploit weaknesses in the cryptography algorithm or its implementation.
In general, the more valuable the information that is to be protected by a key, the shorter the key lifetimes must be. The shorter lifetime not only minimizes the amount of ciphertext available for cryptanalysis, it also limits the damage that is caused if a key is compromised after a successful key attack.