🔒C2PA Allows Time Manipulation Through Image Metadata
Image metadata can now manipulate timestamps
TL;DR
C2PA's metadata feature can be exploited to alter timestamps in images, potentially misleading verification tools. The Pixel 10's trust in device time adds to the risk. Detecting such manipulations is tricky.
C2PA, a metadata standard for images, can be exploited to manipulate timestamps. By excluding parts of the file, a malicious signer can produce a valid signature over an empty string, altering the timestamp without invalidating the signature. This vulnerability is exacerbated by the Pixel 10's trust in device time. Verification tools currently don't flag exclusions, making detection difficult. This could mislead users about the authenticity and timestamp of images. The C2PA specification should enforce stricter constraints on exclusions to prevent such tampering.
Key Points
C2PA's metadata can be altered to produce valid signatures over empty strings, changing timestamps.
Verification tools do not flag exclusions as unusual, making detection difficult.
Pixel 10 trusts device time, increasing the risk of timestamp manipulation.
C2PA's claim signature asserts data existed at-or-before a specified timestamp.
TSA signature asserts the server saw the hash at the specified timestamp.
Why It Matters
If you're using C2PA for image verification, this vulnerability could mislead you about the authenticity and timestamp of images. Verification tools need to enforce stricter constraints on exclusions to prevent tampering. For instance, if you're verifying images for legal or security purposes, this could be a significant risk.
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