About

Elsa4 Apparently, its an instance of LC4 cipher. We are provided with a subtle hint Frozen in time which could mean random is seeded with the present time, confirmed by the fact that time is provided at the start of the challenge. Now, all we need to figure out is the length of nonce, however it is implemented. I also wrote encrypt, decrypt...

Unvreakable Vase We are provided with prompt.txt, which reads zmxhz3tkb2vzx3roaxnfzxzlbl9jb3vudf9hc19jcnlwdg9vb30= This seems to be base64 encoded but I think all the letters are converted to lowercase as hinted by squished and flat import base64 data = 'zmxhz3tkb2vzx3roaxnfzxzlbl9jb3vudf9hc19jcnlwdg9vb30=' m1 = base64.b64decode(data) print...

Twinning The name of the challenge is a subtle hint towards Twin primes, i.e. the RSA primes p and q being twin primes, at a difference of two. How does that help? We can now easily factor n since we have another relation, namely q = p + 2 and p*q = N q^2 - q*p = N ( q - 1 )^2 = N + 1 q = sqrt( N + 1 ) + 1 p = sqrt( N + 1 ) - 1 One c...

Raspberry We are provided with prompt.txt, the contents of which read n = 773520893984898507968061463358178227437114815729335290490531331540941846732272670284818953272149012170851769784825594825465619279367942479695474364981087829268850738595292022948377638992265038873997507258766086698660308098698035921952511158965919117293704786900833198238...

Ooo-la-la We are provided prompt.txt, the contents of which read N = 3349683240683303752040100187123245076775802838668125325785318315004398778586538866210198083573169673444543518654385038484177110828274648967185831623610409867689938609495858551308025785883804091 e = 65537 c = 8776057555426699101543111092257626153215937671876570174951376666623...

Homecooked We are provided decrypt.py, the contents of which read import base64 num = 0 count = 0 cipher_b64 = b"MTAwLDExMSwxMDAsOTYsMTEyLDIxLDIwOSwxNjYsMjE2LDE0MCwzMzAsMzE4LDMyMSw3MDIyMSw3MDQxNCw3MDU0NCw3MTQxNCw3MTgxMCw3MjIxMSw3MjgyNyw3MzAwMCw3MzMxOSw3MzcyMiw3NDA4OCw3NDY0Myw3NTU0MiwxMDAyOTAzLDEwMDgwOTQsMTAyMjA4OSwxMDI4MTA0LDEwMzUzMzcsMTA0Mz...

Docxor Getting hints from the name, one could tell, it is XOR and its about a doc. Still, first thing to consider is running the file command to see whats the homework file is about file homework homework: data Cool! this means, the homework file is simply XOR encryption of a .doc file with 4 byte key. But hey that should ring bells since th...

December We are provided with source.py, which reads #!/usr/bin/env python from Crypto.Cipher import DES with open('flag.txt', 'rb') as handle: flag = handle.read() padding_size = len(flag) + (8 - ( len(flag) % 8 )) flag = flag.ljust(padding_size, b'\x00') with open('key', 'rb') as handle: key = handle.read().strip() iv =...