title: For AES CBC encryption, whats the importance of the IV?
body: <p>What is the security threat of always using all zeroes for the IV?  If it allows the encrypted text to be deciphered, how could an attacker do that?</p>
  
  <p>UPDATE: So then, if the first block of unencrypted data had a timestamp that never repeated, would an IV still be necessary?</p>