Browser-based Poly1305 MAC demo — polynomial evaluation over GF(2¹³⁰−5), constant-time tag verification, key-reuse attack visualizer, and Polynomial Stepper. Part of crypto-lab.

Deal a shuffled deck of cards into a keystream to hands-on teach one-time keys, key reuse attacks, and stream ciphers. Encrypt messages, share via QR, then crack a reused deck with crib dragging. A client-side Cipher Museum PWA with CTF challenge mode and educator materials.

Browser-based one-time pad demo — perfect-secrecy encrypt/decrypt, then the two-time-pad break: XOR two ciphertexts under a reused key and crib-drag to recover both plaintexts. Real XOR over real bytes. No backends. No simulated math.