Why is AES encrypted cipher of the same string with the same key always different?

Question

I have a file called plain.txt. Inside the file I have:

Hello Hello Hello Hello

I am using this command to encrypt it:

openssl          


        

Answer 1

Because the "salt" varies each time. This prevents, for example, rainbow table type attacks on the encrypted values. See http://en.wikipedia.org/wiki/Salt_(cryptography)