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by 3rd3 4249 days ago
Why does it use fuzzed input in the first place? Couldn’t one just use random input from the beginning instead? It would be effectively equivalent but fuzzing of a "hello" string seems to be roundabout.
4 comments

Well, "hello" is pretty random. :) It was probably just used for dramatic effect in the demo, and you have to start with something - of course even a 0 byte file would be enough.

You could also have a started with a valid .jpg with lots of complicated embedded exif metadata sections etc, and have a good chance of triggering bugs in those code paths without having to "discover exif" first.

From the article: it works without any special preparation: there is nothing special about the "hello" string.
He said it took a day to find good jpg images. If you started the program with a valid input, then it would take much less time to explore the other code paths.
In this case "hello" was just a pseudorandom starter to seed the fuzzer.