A HEIC file that computes its own SHA-256 when Apple decodes it
Turning the HEIC decoder into a SHA-256 computer
Researchers built a 536,870,946-byte HEIC file whose final decoded picture spells out the file's own SHA-256 hash. They turned HEVC's intra prediction, residuals, PCM and motion compensation into a fixed-program machine of roughly 150,000 gates, then wrote a compiler that emits the bitstream directly so Apple's stock ImageIO runs the computation. HEVC was far harder than their earlier JPEG XL hashquine because it offers samples and motion vectors instead of a decision tree.
The SHA-256 equations were the easy part. The real work was abandoning abstractions as the evidence killed them: pixels became signal tracks, tracks became a systolic array, values became virtual registers, and one picture became an image sequence with a decoder-supplied state bus.