Description:
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---
From manual page: http://www.php.net/function.mcrypt-encrypt#refsect1-
function.mcrypt-encrypt-examples
---

The mcrypt_encrypt() example shows simple encryption using ECB mode and with no 
message integrity validation. This is then being copied by people in production 
applications, creating vulnerabilies. It would help a lot if the example also 
added HMAC calculation for the message. Its validation should be added to 
mcrypt_decrypt() function.

http://php.net/manual/en/function.hash-hmac.php