You're probably confusing "cryptographic hash functions" with "perceptual hashing" (or other forms of "locality-sensitive hashing"). In the case of the latter,

You're probably confusing "cryptographic hash functions" with "perceptual hashing" (or other forms of "locality-sensitive hashing"). In the case of the latter, what you say is almost always not true (that's the point of using "perceptual hashing" after all: similar objects get mapped to similar/same hash). See: https://en.wikipedia.org/wiki/Perceptual_hashing https://en.wikipedia.org/wiki/Perceptual_hashing