An anonymous reader writes "When data is encrypted, it becomes a garble of "random" characters. With brute force, the attacker keeps trying new keys until one is found that unlocks the encryption. But how does the attacker know that they have succeeded? What is it that tells them that the result they have now is coherent? Please help inform me and others who don't know as much about encryption. Because it seems to me that if a file is encrypted twice, the attacker would never be able to see coherent data from the first unlocking. And apparently that's not true. Why? And why can't encryption be made more resistant to brute force?"