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A comment on Show HN: Perceptual hashing tools for detecting child sexual abuse material. Parent comment

Re:Show HN: Perceptual hashing tools for detecting child sex... by jsjohnst on Monday November 04, 2019 @05:00PM (#21446981)
It’s been a long time since I had to implement PhotoDNA (helped write a PHP native version of the PhotoDNA hash function at Tumblr), can you indicate if pHash creates compatible hashes to PhotoDNA’s output?
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Re:Show HN: Perceptual hashing tools for detecting child sex... by faustomorales on Monday November 04, 2019 @05:13PM (#21447117)
Cool (re: writing a PHP version)! Generally speaking, hashes from different hash algorithms cannot be used with each other.

By the way, would be glad to connect and chat, especially if you have any thoughts on pain points associated with perceptual hashing (email in profile).

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Re:Show HN: Perceptual hashing tools for detecting child sex... by jsjohnst on Monday November 04, 2019 @05:20PM (#21447200)
Does NCMEC support collection and distribution of hashes for alternative functions these days? Six years ago they only supported PhotoDNA hashes (hence why we ported Microsoft’s version of the hash function).

My email is in my profile too, feel free to reach out if I forget.

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Re:Show HN: Perceptual hashing tools for detecting child sex... by jsjohnst on Monday November 04, 2019 @05:16PM (#21447149)
> hashes from different hash algorithms cannot be used with each other

That’s what I thought, but your mention of pHash alluded to it maybe being an open source drop in replacement for PhotoDNA, so I wanted to clarify instead of assuming.

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