ctf writeups ✏️

2022

  • WMCTF 2022

  • UIUCTF 2022

  • MCH 2022

  • ImaginaryCTF 2022

    • Poker: Recover python PRNG behind a modulo
    • Secure Encoding: Base64: Revert substitution cipher on Base64 data using simulated annealing
    • Living Without Expectations: Break learning with errors with closest vector
    • Lorge: Break RSA key with smooth primes using Pollard p-1 attack despite mitigations
    • stream: Reverse binary and derive LCG key
    • hash: Custom hash collision using z3
    • otp: Biased one time pad
  • Google CTF 2022

    • OCR: Leak images in a ML test set with specially crafted model weights
    • Cycling: Recover RSA key from leaked kλ(n)k\lambda(n)
  • International Cybersecurity Challenge 2022

    • Trademark: Attack-defense service with polynomial cryptosystem and authorization bypass
  • SEETF 2022

    • Probability: Recover python PRNG from random.random() output + dynamic programming to win blackjack
    • To Infinity: Pathfinding over finite field using CVP and continued fractions
    • WeirdMachine: Assembly golf with awkward branching behaviour
    • Welcome: Carving QR code from video with opencv
    • Username Generator: XSS using window.name

2021

2020

  • Govtech STACK the Flags 2020

2019 and earlier

  • Facebook CTF 2019
    • keybaseish: Generate valid RSA public key for a fixed signature
  • SwampCTF 2018