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Show HN: Perceptual hashing tools for detecting child sexual abuse material

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Re: Show HN: Perceptual hashing tools for detecting child sexual abuse material

#11

Post by faustomorales »

jsjohnst wrote: post #9
faustomorales wrote: post #2

Hi HN! I'm a data scientist at Thorn, a non-profit dedicated to defending children from sexual abuse. We're excited to open source some elements of our perceptual hashing tooling as a Python package. We've tried to make it very flexible both for ourselves and hopefully also for others. Our aim with is to provide tools that (1) help more people eliminate child sexual abuse material from the internet and (2) assist wit…

Can you comment on how this compares to PhotoDNA? I looked at the readme and was surprised to not see mention of it.

Great question! PhotoDNA is the most well-known and supported hash function for this use case. And we do support hashing and matching with PhotoDNA in the Safer product. However, the PhotoDNA hash function is non-public so we cannot include it in an open source package. We support pHash as an open source alternative so that companies without PhotoDNA licenses can get started with hashing.

Re: Show HN: Perceptual hashing tools for detecting child sexual abuse material

#12

Post by jsjohnst »

faustomorales wrote: post #11
jsjohnst wrote: post #9

Earlier quoted context omitted.

Can you comment on how this compares to PhotoDNA? I looked at the readme and was surprised to not see mention of it.

Great question! PhotoDNA is the most well-known and supported hash function for this use case. And we do support hashing and matching with PhotoDNA in the Safer product. However, the PhotoDNA hash function is non-public so we cannot include it in an open source package. We support pHash as an open source alternative so that companies without PhotoDNA licenses can get started with hashing.

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?

Re: Show HN: Perceptual hashing tools for detecting child sexual abuse material

#14

Post by faustomorales »

jsjohnst wrote: post #12
faustomorales wrote: post #11

Earlier quoted context omitted.

Great question! PhotoDNA is the most well-known and supported hash function for this use case. And we do support hashing and matching with PhotoDNA in the Safer product. However, the PhotoDNA hash function is non-public so we cannot include it in an open source package. We support pHash as an open source alternative so that companies without PhotoDNA licenses can get started with hashing.

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?

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).

Re: Show HN: Perceptual hashing tools for detecting child sexual abuse material

#16

Post by jsjohnst »

faustomorales wrote: post #14
jsjohnst wrote: post #12

Earlier quoted context omitted.

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?

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).

> 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.

Re: Show HN: Perceptual hashing tools for detecting child sexual abuse material

#17

Post by jsjohnst »

faustomorales wrote: post #14
jsjohnst wrote: post #12

Earlier quoted context omitted.

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?

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).

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.

Re: Show HN: Perceptual hashing tools for detecting child sexual abuse material

#18

Post by hnbroseph »

pbalau wrote: post #13

From what I've read, this is supposed to catch the bad thing after it happened, not to prevent it. Then you say that 1 in 1000 is an acceptable error rate. 1 in 7 billions is not an acceptable error rate!

without a "minority report"-esque system, or preemptively putting the entire population in cages, you cannot prevent every ill of the world.
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