4 ms·

What does "manual review" mean then and how are those images reported?

shuckles 5y ago
Before: you would upload images to iCloud Photos. Apple can access your images in iCloud Photos, but it does not. Now: You upload images to iCloud Photos. When doing so, your device also uploads a separate safety voucher for the image. If there are enough vouchers for CSAM matched images in your library, Apple gains the ability to access the data in the vouchers for images matching CSAM. One of the data elements in the voucher is an “image derivative” (probably a thumbnail) which is manually reviewed. If the image derivative also looks like CSAM, Apple files a report with NCMEC’s CyberTip line. Apple can (for now) access the image you stored in iCloud, but it does not. All the data it needs is in the safety voucher. Lot of words spilled on this topic, yet I’d be surprised if a majority of people are even aware of these basic facts about the system operation.
- matwood 5y ago
  Not sure your before is entirely correct. Apple has admitted to scanning iCloud photos, so they are already accessing them at some point. https://digit.fyi/apple-admits-scanning-photos-uploaded-to-icloud/ https://digit.fyi/apple-admits-scanning-photos-uploaded-to-i...
  - shuckles 5y ago
    The before is entirely correct. Only iCloud Mail was previously scanned for CSAM. As a sanity check: it's not plausible that Apple only generated O(100) referrals to CyberTip annually if it were scanning all iCloud Photos. Other services of similar scale generate O(1M) referrals.
- munchler 5y ago
  Thank you for this explanation. Much more helpful than any of the lengthy articles I've read to date. I think Apple has botched the rollout of this change by failing to explain clearly how it works. As a result, rumors and misunderstandings have proliferated instead.
- dmitriid 5y ago
  > access the data in the vouchers for images matching CSAM. One of the data elements in the voucher is an “image derivative” (probably a thumbnail) So the author of the article is technically correct: Apple intentionally uploads CP to their servers for manual review which is explicitly forbidden by law. He even describes the issue with thumbnails
  - shuckles 5y ago
    It is exceedingly unlikely that a system developed with NCMEC’s support and a Fortune 5 legal team somehow fails to comply with the most obviously relevant laws.
    - dmitriid 5y ago
      I'd say: A trillion-dollar company and a government agency can do whatever they feel like, and laws be damned :)
tgsovlerkhgsel 5y ago
As I understand it: When you choose to upload your images to iCloud (which currently happens without end-to-end encryption), your phone generates some form of encrypted ticket. In the future, the images will be encrypted, with a backdoor key encoded in the tickets. If Apple receives enough images that were considered a match, the tickets become decryptable (I think I saw Shamir's Secret Sharing mentioned for this step). Right now, Apple doesn't need that because they have unencrypted images, in a future scheme, decrypting these tickets will allow them to decrypt your images. (I've simplified a bit, I believe there's a second layer that they claim will only give them access to the offending images. I have not studied their approach deeply.)
- shuckles 5y ago
  These are not “claims.” The process by which they get access to only the safety vouchers for images matching CSAM is private set intersection and comes with a cryptographic proof. In no step of the proposal does Apple access the images you store in iCloud. All access is through the associated data in the safety voucher. This design allows Apple to switch iCloud storage to end to end encrypted with no protocol changes.
  - jtc331 5y ago
    What good is end to end encryption if the OS is prebuilt with a method of breaking that encryption? This is definitional backdooring, and you’re back to trusting Apple’s goodwill (and/or willingness to resist governments) to keep your data safe (I.e., not add new decryptable triggers). Not having backdoors is a hard requirement for end to end encryption offering privacy guarantees.
    - shuckles 5y ago
      This is taking the discussion into the realm of hypothetical. If we end up in a world where there are reliable public cloud providers that offer end to end encryption with no content scanning whatsoever, I'll be glad to give them my money.
  - 5y ago

Before: you would upload images to iCloud Photos. Apple can access your images in iCloud Photos, but it does not. Now: You upload images to iCloud Photos. When doing so, your device also uploads a separate safety voucher for the image. If there are enough vouchers for CSAM matched images in your library, Apple gains the ability to access the data in the vouchers for images matching CSAM. One of the data elements in the voucher is an “image derivative” (probably a thumbnail) which is manually reviewed. If the image derivative also looks like CSAM, Apple files a report with NCMEC’s CyberTip line. Apple can (for now) access the image you stored in iCloud, but it does not. All the data it needs is in the safety voucher. Lot of words spilled on this topic, yet I’d be surprised if a majority of people are even aware of these basic facts about the system operation.

matwood 5y ago
Not sure your before is entirely correct. Apple has admitted to scanning iCloud photos, so they are already accessing them at some point. https://digit.fyi/apple-admits-scanning-photos-uploaded-to-icloud/ https://digit.fyi/apple-admits-scanning-photos-uploaded-to-i...
- shuckles 5y ago
  The before is entirely correct. Only iCloud Mail was previously scanned for CSAM. As a sanity check: it's not plausible that Apple only generated O(100) referrals to CyberTip annually if it were scanning all iCloud Photos. Other services of similar scale generate O(1M) referrals.
munchler 5y ago
Thank you for this explanation. Much more helpful than any of the lengthy articles I've read to date. I think Apple has botched the rollout of this change by failing to explain clearly how it works. As a result, rumors and misunderstandings have proliferated instead.
dmitriid 5y ago
> access the data in the vouchers for images matching CSAM. One of the data elements in the voucher is an “image derivative” (probably a thumbnail) So the author of the article is technically correct: Apple intentionally uploads CP to their servers for manual review which is explicitly forbidden by law. He even describes the issue with thumbnails
- shuckles 5y ago
  It is exceedingly unlikely that a system developed with NCMEC’s support and a Fortune 5 legal team somehow fails to comply with the most obviously relevant laws.
  - dmitriid 5y ago
    I'd say: A trillion-dollar company and a government agency can do whatever they feel like, and laws be damned :)

tgsovlerkhgsel 5y ago

As I understand it: When you choose to upload your images to iCloud (which currently happens without end-to-end encryption), your phone generates some form of encrypted ticket. In the future, the images will be encrypted, with a backdoor key encoded in the tickets. If Apple receives enough images that were considered a match, the tickets become decryptable (I think I saw Shamir's Secret Sharing mentioned for this step). Right now, Apple doesn't need that because they have unencrypted images, in a future scheme, decrypting these tickets will allow them to decrypt your images. (I've simplified a bit, I believe there's a second layer that they claim will only give them access to the offending images. I have not studied their approach deeply.)

shuckles 5y ago
These are not “claims.” The process by which they get access to only the safety vouchers for images matching CSAM is private set intersection and comes with a cryptographic proof. In no step of the proposal does Apple access the images you store in iCloud. All access is through the associated data in the safety voucher. This design allows Apple to switch iCloud storage to end to end encrypted with no protocol changes.
- jtc331 5y ago
  What good is end to end encryption if the OS is prebuilt with a method of breaking that encryption? This is definitional backdooring, and you’re back to trusting Apple’s goodwill (and/or willingness to resist governments) to keep your data safe (I.e., not add new decryptable triggers). Not having backdoors is a hard requirement for end to end encryption offering privacy guarantees.
  - shuckles 5y ago
    This is taking the discussion into the realm of hypothetical. If we end up in a world where there are reliable public cloud providers that offer end to end encryption with no content scanning whatsoever, I'll be glad to give them my money.
- 5y ago