The Cipher Challenge Contest
Four degrees of difficulty, from pen & paper to complex mathematical problems
Solved Level 2 challenge Twisting the Rubik's Cube
Solved Level 1 challenge MACs in Orbit
Solved Level 1 challenge Number Sequence — Part 8
Solved Level 1 challenge Grille Cipher
Solved Level 1 challenge Factorization Cipher — Part 1
Solved Level 1 challenge Advent-Challenge — Part 1
Solved Level 1 challenge Affine Codes / Modulo Arithmetic with N / Extended Euclid
Solved Level 2 challenge Cracking SHA1-Hashed Passwords
Four degrees of difficulty, from pen & paper to complex mathematical problems