0xv1n.github.iowriteupHackTheBox | xorxorxor
A HackTheBox crypto challenge writeup ('xorxorxor') walking through how to break a weak custom encryption scheme where a flag is XOR-encrypted with a 4-byte repeating key generated via os.urandom(4). The author demonstrates a known-plaintext attack: since HTB flags always start with 'HTB{', the first 4 known plaintext bytes are XORed against the ciphertext to recover the full key, which is then used to decrypt the rest of the flag. It's a beginner-friendly explainer of XOR logic and how key reuse/short keys make repeating-key XOR trivially breakable with known-plaintext.
TL;DR HTB crypto challenge writeup showing how a known 'HTB{' plaintext prefix reveals a 4-byte repeating XOR key, fully breaking the flag's encryption.
Organisations named here
- known-plaintext attack
Technologies named here
- challenge.py
- Online XOR tool
- Hex to binary converter
- ASCII Table
- Python
Techniques named here
- Known-plaintext attack against XOR encryption
Related in Learning
hausec.comwriteupCreating a Red & Blue Team Homelab
bencteux.frarticleELearnSecurity Certified Threat Hunting Professional (eCTHPv2) review
protocolsoup.comtoolProtocol Soup
0xv1n.github.iowriteup