why AES encryption is faster than Decryption

Question

I developed an encrypion system using AES, as i read, AES is symmetric and thus it takes the same period of time to encrypt and decrypt a particular file .. in my case, i got encryption time shorter than decryption time eventhough I iterate the encryption and decryption for the same file more than 20 times.

any justiication why am I getting different time for encryption or decryption ?!

Answer 1

Symmetric points to the fact that it uses the same key to encrypt and decrypt, and has nothing to do with the encryption and decryption functions themselves. Algorithms generally perform differently depending on their implementation. That said, the opposite of your question has been asked on the Security StackExchange: https://security.stackexchange.com/questions/38055/why-does-aes-encryption-take-more-time-than-decryption