Tags: cryptography caesar crypto 

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[Full write-up here](https://github.com/doublestandardctf/WPICTF2019/blob/master/zoomercrypt.md)

The problem gave [an image](https://drive.google.com/file/d/1BO3v97Igzs7KruDkK7B4AGqxsNB7BaWE/view) and ask you to find the encrypted message inside.

There are two notable things in this image: the reference to ROT15 in the third message and the large number of emoji, plus curly braces and an underscore in between them.

From the reference to ROT15, we thought that there would be something with the unicode values of the emoji characters connecting to the unicode values of the letters in the messages.

When we took the unicode values of the emoji, we noticed that they were all between 0x1F601 and 0x1F619, which is as large of a range as the ASCII upper case letters.

When we subtracted 0x1F5C0 from the unicode values for each of the emoji, we got text that said, "CAU WH WG KDW{FSDSBH_NCCASFG}".

From there, our next thought was something with rotations, because that looks a lot like there's a flag at the end of that message. By using [this site](http://rumkin.com/tools/cipher/caesar.php), we checked and noticed that KDW becomes WPI (which is what the flag begins with) when rotated by twelve positions through the alphabet. By rotating the entire thing 12 positions, then the message becomes "OMG IT IS WPI{REPENT_ZOOMERS}". The last part of that is the flag.