In this post, I’ll collect links on Apple’s iPhone backdoor for scanning CSAM images. Previous links are here and here.
Apple says that hash collisions in its CSAM detection system were expected, and not a concern. I’m not convinced that this secondary system was originally part of the design, since it wasn’t discussed in the original specification.
Good op-ed from a group of Princeton researchers who developed a similar system:
Our system could be easily repurposed for surveillance and censorship. The design wasn’t restricted to a specific category of content; a service could simply swap in any content-matching database, and the person using that service would be none the wiser.
EDITED TO ADD (8/30): Good essays by Matthew Green and Alex Stamos, Ross Anderson, Edward Snowden, and Susan Landau. And also Kurt Opsahl.
EDITED TO ADD (9/6): Apple is delaying implementation of the scheme.
Posted on August 20, 2021 at 8:54 AM •
New paper: “Encrypted Cloud Photo Storage Using Google Photos.”
Abstract: Cloud photo services are widely used for persistent, convenient, and often free photo storage, which is especially useful for mobile devices. As users store more and more photos in the cloud, significant privacy concerns arise because even a single compromise of a user’s credentials give attackers unfettered access to all of the user’s photos. We have created Easy Secure Photos (ESP) to enable users to protect their photos on cloud photo services such as Google Photos. ESP introduces a new client-side encryption architecture that includes a novel format-preserving image encryption algorithm, an encrypted thumbnail display mechanism, and a usable key management system. ESP encrypts image data such that the result is still a standard format image like JPEG that is compatible with cloud photo services. ESP efficiently generates and displays encrypted thumbnails for fast and easy browsing of photo galleries from trusted user devices. ESP’s key management makes it simple to authorize multiple user devices to view encrypted image content via a process similar to device pairing, but using the cloud photo service as a QR code communication channel. We have implemented ESP in a popular Android photos app for use with Google Photos and demonstrate that it is easy to use and provides encryption functionality transparently to users, maintains good interactive performance and image quality while providing strong privacy guarantees, and retains the sharing and storage benefits of Google Photos without any changes to the cloud service
Posted on July 30, 2021 at 6:34 AM •
Sidebar photo of Bruce Schneier by Joe MacInnis.