Blue Alder

Angstrom 2019 – Powerball Writeup

Powerball Category: CryptoPoints: 200Description: Introducing ångstromCTF Powerball, where the Grand Prize is a flag! All you need to do is guess 6 ball values, ranging from 0 to 4095. But don’t worry, we’ll give one for free! Interesting RSA challenge which I liked. The premise of the challenge is that that server picks 6 numbers between 0-4095 and […]

Angstrom 2019 – Pie Shop Writeup (bad)

Pie Shop Category: BinaryPoints: 100Description: I sure love pies (source)! The biggest fluke of my LIFE. Okay so this was another simple buffer overflow again using the gets() call. BUT PIE (position independent executable) is enabled on this binary which means that the addresses of the functions within the binary change. Kinda like ASLR but inside the binary. […]

Angstrom 2019 – Chain of Rope Writeup

Chain of Rope Category: BinaryPoints: 80Description: defund found out about this cool new dark web browser! While he was browsing the dark web he came across this service that sells rope chains on the black market, but they’re super overpriced! He managed to get the source code. Can you get him a rope chain without paying? Fun fact […]

Angstrom 2019 – Aquarium Writeup

Aquarium Category: BinaryPoints: 50Description: Here’s a nice little program that helps you manage your fish tank. Super simple buffer overflow challenge. They use the gets() function which reads an unlimited amount of input which is able to overwrite the stack. Using a cylic pattern in gdb to detect where the offset is we find that the $rsp overwrite […]

Angstrom 2019 – Cookie Cutter Writeup

Cookie Cutter Category: WebPoints: 200Description: I stumbled upon this very interesting site lately while looking for cookie recipes, which claims to have a flag. However, the admin doesn’t seem to be available and the site looks secure – can you help me out? This was an awesome challenge of both javascript quirks and jsonwebtokens which are awesome! Looking […]

Angstrom 2019 – Secret Sheep Society Writeup

Secret Sheep Society Category: CryptoPoints: 120Description: The sheep are up to no good. They have a web portal for their secret society, which we have the source for. It seems fairly easy to join the organization, but climbing up its ranks is a different story. I really liked this challenge. This was to do with bit flipping an […]

Angstrom 2019 – Runes Writeup

Runes Category: CryptoPoints: 70Description: The year is 20XX. ångstromCTF only has pwn challenges, and the winner is solely determined by who can establish a socket connection first. In the data remnants of an ancient hard disk, we’ve recovered a string of letters and digits. The only clue is the etching on the disk’s surface: Paillier. Cool so for […]

Angstrom 2019 – High Quality Checks Writeup

High Quality Checks Category: RevPoints: 110Description: After two break-ins to his shell server, kmh got super paranoid about a third! He’s so paranoid that he abandoned the traditional password storage method and came up with this monstrosity! I reckon he used the flag as the password, can you find it? This challenge was a bitch to work through. […]