2025from public repositories
PCC Qualifiers 2025
2 challenges with 2 published solutions between them. The writeups for this event were found in public repositories. Each link is pinned to the commit it was read from.
Where these writeups liveCryptography2
Recover a plaintext or a key from something that was supposed to protect it. In practice: identify the scheme, find the parameter the author got wrong, exploit it.
Solve it with:Cipher identifier and automatic decoderVigenere cipher solver with automatic key recoveryRSA decryption and attack runnerWiener’s attack on small RSA private exponentsIn-browser hash cracker with rule transformsLearn: Classical ciphers and frequency analysisLearn: RSA and the parameters that break it
Biggie
1 official solutionAlso written up in: president-xd/Writeups
Square
1 official solutionAlso written up in: president-xd/Writeups