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Re: Chartering work has started for a Linked Data Signature Working Group @W3C

From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
Date: Fri, 4 Jun 2021 09:22:26 -0400
To: semantic-web@w3.org
Message-ID: <8275fbcc-c3ee-1037-e60b-ca62e3a31bbf@gmail.com>
I'm just keeping one of the attacks here - the one I feel is most important.

On 6/3/21 5:01 PM, Manu Sporny wrote:
>> Here are several attacks that I believe can be carried out against the
>> algorithms in https://w3c-ccg.github.io/ld-proofs/#algorithms.
> None of the attacks work, details below.

[...]

>
> Attack 2 is less difficult but requires something like the JSON-LD @context
>   mechanism.   A producer signs a document that has a remote context that is
>   under the control of a third party.  The consumer verifies the signed
> document, which is successful because the first time the consumer asks for
> the remote context the same information is sent, and sent as expiring
> immediately.  The third party then sends different remote context the next
>   time the consumer asks for it so that when the consumer deserializes the
> signed document the consumer sees an RDF dataset that is not what the
> producer signed.
> Invalid. If the RDF Dataset is not what the producer signed, the signature
> fails verification.
>
Not so.  The validation succeeds because it sees the RDF dataset the producer 
signed.  The consumer sees a different dataset because the third party changes 
the remote context between the time the verification is done and the time that 
the consumer extracts the dataset from the document.

One reason I want an implementation of the algorithms as commands is to show 
exactly how this attack works against the algorithms.

[...]

peter
Received on Friday, 4 June 2021 13:24:21 UTC

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