# What is the “artificial abort” technique?

In the security proof of Brent Waters's paper Efficient Identity-Based Encryption Without Random Oracles, he uses a novel “artificial abort” step on page 6.

At this point the simulator is still unable to use the output from the adversary. An adversary’s probability of success could be correlated with the probability that the simulator needs to abort. This stems from the fact that two different sets of $q$ private key queries may cause the simulator to abort with different probabilities.

What is the purpose of this step? Also, I am confused by the first sentence above. What goes wrong if I just use the output from the adversary without this artificial abort step?

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