Third post in the TraceBash CTF 2026 series on this site. The earlier ones cover crypto (small-subgroup DH, shared RSA prime, harmonic XOR, 16-bit seed brute) and OSINT (geocaching pivot, Plus Codes, NYC DOB open data, cross-platform handle pivoting). This one walks the two pwn challenges in the same step-by-step format. ...
Second post in the TraceBash CTF 2026 series on this site. The crypto writeup covered four cryptographic mistakes (small-subgroup DH, shared RSA prime, harmonic-XOR key recovery, 16-bit-seed brute). This one covers the four OSINT challenges in the same step-by-step format. The TraceBash OSINT track is a careful mix of techniques. echo-chamber is about filtering one specific clue out of a noisy forum post. missing-friend chains visual anchors in two photos into a Google Plus Code. permit-pending is the 310-point headline: a single street-scene photo plus the NYC Department of Buildings open-data API. retired-hacker is cross-platform handle pivoting (Komoot → GitHub → Threads → a Romanian tram stop). None of these challenges requires private databases, paid scrapers, or shady tools. All four use public web records, official open-data APIs, or open-source platforms in their normal documented modes. ...
TraceBash CTF 2026 is a Jeopardy-style CTF with a clean, well-curated challenge set. The crypto track has four challenges, three at 100 points and one at 440 points. This writeup covers all four step-by-step. Each challenge is a different shape of cryptographic mistake. state-desync hides a 16-bit-seed stream cipher behind a noisy update function. broken-trust-protocol is a textbook Diffie-Hellman implementation that forgets to validate the peer public value. harmonic-cipher hides an 8-byte XOR key inside an audio file. quantum-echo ships two RSA-1024 public keys that share a 512-bit prime, where a single gcd factors both moduli in milliseconds. None of them requires sage, lattice work, or anything more exotic than a careful read and a small Python brute. All four exist in production code somewhere in the wild. ...