Apple Outlines Security and Privacy of CSAM Detection System in New Document

Apple today shared a document that provides a more detailed overview of the child safety features that it first announced last week, including design principles, security and privacy requirements, and threat model considerations.

iphone communication safety feature
Apple’s plans to detect known Child Sexual Abuse Material (CSAM) images stored in iCloud Photos has been particularly controversial and has prompted concerns from some security researchers, the non-profit Electronic Frontier Foundation, and others about the system potentially being abused by governments as a form of mass surveillance.

The document aims to address these concerns and reiterates some details that surfaced earlier in an interview with Apple’s software engineering chief Craig Federighi, including that Apple expects to set an initial match threshold of 30 known CSAM images before an iCloud account is flagged for manual review by the company.

Apple also said that the on-device database of known CSAM images contains only entries that were independently submitted by two or more child safety organizations operating in separate sovereign jurisdictions and not under the control of the same government.

The system is designed so that a user need not trust Apple, any other single entity, or even any set of possibly-colluding entities from the same sovereign jurisdiction (that is, under the control of the same government) to be confident that the system is functioning as advertised. This is achieved through several interlocking mechanisms, including the intrinsic auditability of a single software image distributed worldwide for execution on-device, a requirement that any perceptual image hashes included in the on-device encrypted CSAM database are provided independently by two or more child safety organizations from separate sovereign jurisdictions, and lastly, a human review process to prevent any errant reports.

More details to follow…

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