AES Avalanche Diffusion Map: Bit-Flip Probability by Round

Symmetric block ciphers like AES are only secure if a tiny input change — a single flipped bit — becomes statistically indistinguishable from a coin flip in every output bit after enough rounds. This 2D simulator runs a real, independently-implemented AES-128 key schedule and round function across thousands of Monte-Carlo trials, each with a fresh random key and a plaintext pair differing by exactly one bit, and accumulates a 128-bit × 11-round heatmap of how often each individual output bit actually flips. The result is the strict avalanche criterion made visible directly as data: a perfectly certain single bit at round 0 fanning out, within a handful of rounds, into a uniform field of 50% probabilities across the whole state — the statistical signature that makes AES ciphertext resistant to differential cryptanalysis.