Re: [Teep] OTrP Signature Security issue

[Hannes Tschofenig <[e-mail]>]

Hi Anders,

Thanks for raising this point.

I have been wondering whether a JSON encoding is the best choice for TEEP since web developers shouldn't actually be exposed to any of it.

Hence, my question to you is whether you have looked into COSE as well and whether your assessment would be different.

Ciao
Hannes

-----Original Message-----
From: TEEP <[e-mail]> On Behalf Of Anders Rundgren
Sent: Tuesday, November 20, 2018 9:57 PM
To: [e-mail]
Subject: [Teep] OTrP Signature Security issue

The following is a for brevity simplified version of the OTrP signature scheme.  That OTrP rather uses the JSON serialized version of JWS has no security advantages (or disadvantages) over the JWS compact notation shown here:
{
    "carObject":  "eyetc.eyetc.xyxetc"
}

Since "carObject" isn't signed, you can replace it with anything else and the signature will still validate.


Using detached JWS combined with JCS [1,2] you sign the entire JSON object as well as getting the "payload" in clear:
{
    "carObject": {
       "brand":  "Ferrari",
       "horsePower":  "450",
       "weight":  "2357kg"
    },
    "signature": "eyetc..xyect"
}

thanx,
Anders

1] https://tools.ietf.org/html/draft-rundgren-json-canonicalization-scheme-01
2] https://mobilepki.org/jws-jcs

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