Description:

Shal has got a binary. It contains the name of a wise man and his flag. He is unable to solve it.

Submit the flag to unlock the secrets of the universe.

main.exe

In this challenge we have a binary, I ran file command on it:

Megabeets$ file ./main.exe
main.exe: ELF 64-bit LSB  executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.32, BuildID[sha1]=4b9b47b7eac612e0c367f0e3a9878eb1f09b841d, not stripped
root:/mnt/d/

 

Haha, weird. It is actually an ELF file and not exe. Lets execute the binary and give it the answer to everything (’42’) as an input:

Megabeets$ ./main.exe
Gimme: 42
Cipher from Bill
Submit without any tags
#kdudpeh

At first I though that “#kdudpeh” is the flag but it isn’t, neither “kdudpeh”. The name of the person in the question is Shal, looking like SHA1, and the binary says “submit without any tags”, so “hashtagkdudpeh” without the tag is just “hashkdudpeh”. So I tried to submit the result of SHA1(“kdudpeh”) as answer but failed again. Then I tried Caesar cipher on “kdudpeh” and find “harambe”.

So I again tried submit the flag, this time with Sha1(“harabe”).

The flag was pragyanctf{31a0d851ea10ad886ad4e99ed05892de06998ab9} which is SHA1("harambe")