Please implement support for Blind Key Rotation (privacy feature) #398
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Reference: Plume/Plume#398
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Delete branch "%!s()"
Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?
Background
Blind Key Rotation is a mitigation for the problem that JSON-LD Linked Data Signatures are irrevocable. It is also useful (albeit less so) in the context of HTTP Signatures, since HTTP Signatures only sign headers and not the object itself, and are also detached from the object.
As Plume implements JSON-LD Linked Data Signatures, implementing Blind Key Rotation is important for resolving trust and safety issues with this signature scheme!
Implementation - receiving objects
Supporting Blind Key Rotation in the validation pipeline is simple enough: if a signature validation fails, refetch the remote actor and recheck the signature accordingly.
This would be done here:
80a4dae8bd/src/routes/instance.rs (L188-L193)
Implementation - deleting objects
Supporting Blind Key Rotation to enhance the deniability of deleted objects is also simple enough: send the
Delete
signed with the original key and then silently replace the keypair. The new keys will be fetched when the user publishes new content.I'm not quite certain where to implement this part, but it is probably not that hard to implement.
Questions?
Contact me on fediverse: https://pleroma.site/kaniini
An activity pub user has also opened a small bounty for this https://social.holdmybeer.solutions/objects/44515888-e4c2-4043-b0e8-96e15b7a254c
So if I understood well:
Delete
(doUndo
s count too?) : sign with the current key, then regenerate a new oneAm I right?
I have a few more questions:
original key
(in deleting Object) need to be the one which was used in theCreate
activity, or can it be an other key assuming something else was deleted between creation and deletion of this Object?https://<domain>/@/<user>/#main-key
. Should this value be updated whenever a new key is issued, or not?Delete
activity is sent, or some time later (how much?) to make sure instances who did not know the key for thisDelete
can still fetch it to validate the deletion?@fdb-hiroshima
Your understanding is basically correct. I would suggest rotating the key a little while after the
Delete
so if there's multipleDelete
activities you can batch them together.The original key should be whatever key would normally sign the Delete.
The key ID should not ever be updated when rotated.