Apple Says NeuralHash Tech Impacted by 'Hash Collisions' Is Not the Version Used for CSAM Detection

Developer Asuhariet Yvgar this morning said that he had reverse-engineered the NeuralHash algorithm that Apple is using to detect Child Sexual Abuse Materials (CSAM) in iCloud Photos, posting evidence on GitHub and details on Reddit.

Child Safety Feature Blue
Yvgar said that he reverse-engineered the NeuralHash algorithm from iOS 14.3, where the code was hidden, and he rebuilt it in Python. After he uploaded his findings, another user was able to create a collision, an issue where two non-matching images share the same hash. Security researchers have warned about this possibility because the potential for collisions could allow the CSAM system to be exploited.

In a statement to Motherboard, Apple said that the version of the NeuralHash that Yvgar reverse-engineered is not the same as the final implementation that will be used with the CSAM system. Apple also said that it made the algorithm publicly available for security researchers to verify, but there is a second private server-side algorithm that verifies a CSAM match after the threshold is exceeded, along with human verification.

Apple however told Motherboard in an email that that version analyzed by users on GitHub is a generic version, and not the one final version that will be used for iCloud Photos CSAM detection. Apple said that it also made the algorithm public.

"The NeuralHash algorithm [... is] included as part of the code of the signed operating system [and] security researchers can verify that it behaves as described," one of Apple's pieces of documentation reads. Apple also said that after a user passes the 30 match threshold, a second non-public algorithm that runs on Apple's servers will check the results.

Matthew Green, who teaches cryptography at Johns Hopkins University and who has been a vocal critic of Apple's CSAM system, told Motherboard that if collisions "exist for this function," then he expects "they'll exist in the system Apple eventually activates."

"Of course, it's possible that they will re-spin the hash function before they deploy," he said. "But as a proof of concept, this is definitely valid," he said of the information shared on GitHub.

Because of the human element, though, another researcher, Nicholas Weaver, told Motherboard that all people can do with manipulating non-CSAM hashes into CSAM is "annoy Apple's response team with garbage images until they implement a filter" to get rid of false positives. Actually fooling Apple's system would also require access to the hashes provided by NCMEC and it would require the production of over 30 colliding images, with the end result not fooling the human oversight.

Apple is using its NeuralHash system to match a database of image hashes provided by agencies like the National Center for Missing Children (NCMEC) to images on user devices to search for CSAM. The system is designed to produce exact matches and Apple says there's a one in a trillion chance that an iCloud account can be accidentally flagged.

Apple is planning to implement the NeuralHash CSAM system in iOS and iPadOS 15 as part of a suite of child safety features, and it has been a hugely controversial decision with Apple receiving criticism from customers and privacy advocates. Apple has been attempting to reassure customers and security researchers about the implementation of the system with additional documentation and executive interviews.

Popular Stories

iOS 26 on Three iPhones

Here's When to Expect the iOS 26 Public Beta

Tuesday July 15, 2025 11:07 am PDT by
Apple previously announced that a public beta of iOS 26 would be available in July, and now a more specific timeframe has surfaced. Bloomberg's Mark Gurman today said that Apple's public betas should be released on or around Wednesday, July 23. In other words, expect the public betas of iOS 26, iPadOS 26, macOS 26, and more to be available at some point next week. Apple will be releasing...
iPhone 17 Colors

All 15 New iPhone 17 and iPhone 17 Pro Colors Revealed in Latest Leak

Wednesday July 16, 2025 6:50 am PDT by
We may finally have a definitive list of all color options for the iPhone 17 series, ahead of the devices launching in September. MacRumors concept In a report for Macworld today, Filipe Espósito said he obtained an "internal document" that allegedly reveals all of the color options for the upcoming iPhone 17, iPhone 17 Air, iPhone 17 Pro, and iPhone 17 Pro Max models. The report includes ...
Apple Watch Ultra 2 Complications

Apple Watch Ultra 3: What to Expect

Sunday July 13, 2025 10:30 am PDT by
The long wait for an Apple Watch Ultra 3 is nearly over, and a handful of new features and changes have been rumored for the device. Below, we recap what to expect from the Apple Watch Ultra 3:Satellite connectivity for sending and receiving text messages when Wi-Fi and cellular coverage is unavailable 5G support, up from LTE on the Apple Watch Ultra 2 Likely a wide-angle OLED display that ...
Apple Hornsby

Apple Store Near Sydney Permanently Closing Later This Year

Monday July 14, 2025 6:14 pm PDT by
Apple today said its store at the Westfield Hornsby shopping mall, in Hornsby, Australia, will be permanently closing in October. Apple Hornsby In a statement shared with Australian tech news website EFTM (via Reddit), Apple said that it has decided not to renew its lease at Westfield Hornsby. Apple said all affected retail employees will be given the opportunity to work at Apple's nearby...
iPhone 17 Pro in Hand Feature Lowgo

iPhone 17 Pro Coming Soon With These 16 New Features

Friday July 11, 2025 12:40 pm PDT by
Apple's next-generation iPhone 17 Pro and iPhone 17 Pro Max are only two months away, and there are plenty of rumors about the devices. Below, we recap key changes rumored for the iPhone 17 Pro models. Latest Rumors These rumors surfaced in June and July:A redesigned Dynamic Island: It has been rumored that all iPhone 17 models will have a redesigned Dynamic Island interface — it might ...
Foldable iPhone 2023 Feature Homescreen

Foldable iPhone's Thickness and Price Range Detailed in New Reports

Wednesday July 16, 2025 11:31 am PDT by
Apple's long-rumored foldable iPhone will likely have a starting price between $1,800 and $2,000 in the U.S., analysts at investment banking firm UBS said this week. If so, the foldable iPhone would cost more than a MacBook Pro, which starts at $1,599. With a starting price of at least $1,800, the foldable iPhone would be the most expensive iPhone model ever released, topping the Pro Max at...
iPhone 17 Pro Dark Blue and Orange

Ranked: The Best Features Rumored for the iPhone 17 Lineup

Wednesday July 16, 2025 4:17 pm PDT by
We have just under two months to go until the debut of Apple's iPhone 17 models, and rumors have been ramping up in recent weeks. We went through everything we know so far, pulling out the most exciting rumors and highlighting some other changes that aren't going to be so great. Top Tier Ultra Thin iPhone 17 Air - The iPhone 17 Air is 2025's most exciting iPhone rumor, because it's the...

Top Rated Comments

locovaca Avatar
51 months ago
Make it all public. It’s for the children, right? What do you have to hide, Apple?
Score: 63 Votes (Like | Disagree)
miniyou64 Avatar
51 months ago
People giving Apple the benefit of the doubt here are making a tremendous amount of assumptions. This kind of tech never remains only for its intended use. No matter which way you spin it (for the children!) this is invasive. Someone on Twitter mentioned what happens if someone airdrops you a bunch of illicit photos and they sync to iCloud in a matter of seconds? Boom you’re flagged. There’s 1,000,000 ways for this system to go wrong or be exploited or worse ruin innocent peoples lives. And if you do end up being one of those people, you will have exactly zero recourse to prove your innocence. It’s over for you. This entire thing is very stupid on Apple’s part.
Score: 58 Votes (Like | Disagree)
zakarhino Avatar
51 months ago
*amateur devs exploit the system within a few hours of discovery*

Apple: "Uhhh guys, this is totally not the finished algorithm! Believe us!"
Score: 47 Votes (Like | Disagree)
dguisinger Avatar
51 months ago
As Rene Ritchie says on MacBreak Weekly, Apple keeps talking down to us as if we don't understand, and our response is "You don't understand, we understand and do not like this"
Score: 42 Votes (Like | Disagree)
nawk Avatar
51 months ago
Wait - I’m confused by this. Does this mean that everyone’s iCloud is going to be scanned without user’s authorization in the name of child welfare??

While I am sure people may agree with this, it seems like one step away from doctors/dentists submitting DNA samples of *every* patient because it is in the public interest.

This program seems just a small morale slip away from being an invasion of privacy on a monumental scale. Give what Snowden revealed the US government has a huge thirst for data collection like this. It’s a short hop to scan for compromising photos of your political rivals, yes?
Score: 42 Votes (Like | Disagree)
LDN Avatar
51 months ago

Make it all public. It’s for the children, right? What do you have to hide, Apple?
Yeah, this is increasingly sounding like its not meant for children. Not forgetting the fact that actual pedos, who are likely very small in number, will either just turn off iCloud Photos or get Android phones. Normal people are left stuck with the bill. Apple are going to have to pull this whole thing.
Score: 39 Votes (Like | Disagree)