Brainy's Cipher

Name: Brainy's Cipher
Hint: Brainy likes playing around with esoteric programming. He also likes math and has therefore encrypted his very secure password with a popular encryption algorithm. Claiming that his password cannot be retrieved now, he has sent the ciphertext to some of his friends. Can you prove to Brainy that his password can actually be recovered
Base Points: Easy - Retired [0]
Rated Difficulty:
Agent22
Creator: k4m4

We start with a text file again.

 
++++++++++[>+>+++>+++++++>++++++++++>>>+++++++++++++++++++++++.-----------.+.-------------.++++++++++++.------------.+++++++++++++.--------------.++++++++++++++++++++++++++.

The hint provided is:

 
Brainy likes playing around with esoteric programming. He also likes math and has therefore encrypted his very secure password with a 
popular encryption algorithm.  Claiming that his password cannot be retrieved now, he has sent the ciphertext to some of his friends. Can 
you prove to Brainy that his password can actually be recovered?

Looking up Esoteric Programming languages, we find one called "Brainfuck" which would fit with the name of the challenge.  Plugging the string into a Brainfuck decoder we get:

 
 {p:7901324502264899236349230781143813838831920474669364339844939631481665770635584819958931021644265960578585153616742963330195946431321644921572803658406281,
q:12802918451444044622583757703752066118180068668479378778928741088302355425977192996799623998720429594346778865275391307730988819243843851683079000293815051,
dp:5540655028622021934429306287937775291955623308965208384582009857376053583575510784169616065113641391169613969813652523507421157045377898542386933198269451,
dq:9066897320308834206952359399737747311983309062764178906269475847173966073567988170415839954996322314157438770225952491560052871464136163421892050057498651,
c:620780866774166868671838579573503383144462809126733924480650268502126853265511839620564959645797823253020820543939336822657728027508872936024325129679948055
49965020916953644635965916607925335639027579187435180607475963322465417758959002385451863122106487834784688029167720175128082066670945625067803812970871
}

Well, that looks like something that I saw in PicoCTF a while back.  Searching the string in Google provides:

 

https://github.com/zionspike/ctf-writeup/blob/master/Crypto/%5BpicoCTF%202017%5D%20-%20Weird%20RSA%20-%2090/kapi-note.md

 

Chainging the values in the PicoCTF solve.py script to our values and running it, then add the HTB{} around it, we get the flag:  HTB{ch1n3z_r3m4ind3r_the0rem_r0ck$$$_9792}