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by rgbrenner 3976 days ago
the real benefit would be to dedupe every resource on the Internet

Hopefully not. Even if we ignore the possibility of hash collisions (since that's not that likely yet with SHA 256).. There's still the issue of cross origin data leakage. Using a known hash and whether a request is made for the resource to tell if a user has visited another website.

This should require a cors header
1 comments
smilliken 3976 days ago
A common solution to this problem is salting the sensitive value before it's hashed. Then we can have de-duplication and security.
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rgbrenner 3976 days ago
No. Do you understand the attack I'm referring to?

(Legitimate) Site A sends file a.com/image.png w/ a hash.

(Attacker) Site B sends file b.com/image.png w/ identical hash. If no request is made for b.com/image.png, the attacker knows the visitor has gone to Site A.

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smilliken 3969 days ago
To clarify: the hash for the sensitive resource can be salted, making the hash unique and avoiding de-duplication. For non-sensitive resources, eg jquery.js, we can use an unsalted hash and get de-duplication.

Another benefit of identify resources by their hash is that we don't need to request them from a specific host. Instead, you can get them from any CDN that has a matching resource.

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