crypto/dream-revenge

11 solves / 495 points

Writeup by Aryan

I did not solve this problem during the competition. However, the reason is not because I didn't have the solution. I solved dream at 7:30 AM, and went to go take a shower immediately after. When I came back, I began taking a look at other challenges, and didn't realize there was a dream-revenge.

The worst part of the whole situation is that my solution for dream worked on the revenge without any modifications. I didn't realize the seed was hardcoded in dream, but many people did, and they were able to get all of the 624 randomly generated numbers and use randcrack to reverse the seed. This is why the solve count was so high.

dream-revenge randomly generated a new seed every time, meaning users had to deduce the seed with 8 randomly generated numbers. This is what my solution did. If only I had seen the challenge...

If you are here for an actual writeup, see crypto/dream.

Flag: vsctf{couldnt_be_me_using_a_test_version_on_server_oops_f9821112b89a25be}