All Writeups

Comprehensive collection of CTF challenges, solutions, and insights.

2026-05-10 Reverse Engineering Hard

Raptor Weekly 2 - ECHELON Rev 1 - 4.1 ; REMNANT

Reversing a stripped x86-64 ELF to recover Diffie-Hellman parameters with a smooth group order, applying Pohlig-Hellman to recover the private key, and decrypting a C2 beacon payload to extract a handshake key and the flag. Or just running the binary.

reverse-engineering crypto diffie-hellman pohlig-hellman

2026-03-01 Crypto Hard

DEADROP Crypto 5 - DSC-1.1

A fake internal cipher spec documents the agency's homemade DSC-1.1 block cipher, a 2-round Feistel with a trivially invertible round function. Read the spec, implement decryption, and recover the encrypted memo.

custom-crypto feistel reverse-engineering stream-cipher

2026-02-28 Reverse Engineering Hard

WHAMazon! Rev 2 - Armor

Identifying a PyArmor v9.x protected Python script, generating the correct runtime to execute it, and extracting a base64-encoded flag from the crash dump it writes to disk.

pyarmor python obfuscation deobfuscation