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I'm actually guessing not. It's probably something similar algorithm-wise to what Shazam does. Probably not a crypto-hash, but more likely a hashing of robust f

I'm actually guessing not. It's probably something similar algorithm-wise to what Shazam does. Probably not a crypto-hash, but more likely a hashing of robust features (in a relative as opposed to absolute location form) detected from the image to give a "fingerprint." Such features would be robust to scaling and most compression artifact issues. EDIT: Here's a good example: http://laplacian.wordpress.com/2009/01/10/how-shazam-works/ http://laplacian.wordpress.com/2009/01/10/how-shazam-works/

tptacek 12y ago
If this is Microsoft's hash algorithm, the one from the robust image hashing paper, it's not perceptual (like Shazam); it's coding-theoretic. If I understand it correctly, it leaves room for false negatives from drastic (but intelligible) image changes in favor of avoiding false positives from attackers trying to deliberately trip it with non-matching images.