+1 Can we please stop confusing signing and MAC?
On Nov 6, 2012, at 10:54 AM, Jim Schaad <[email protected]> wrote: > <personal> > > Only if you have a really loose definition of signing - it gives you an > integrity check but not origination which is usually implied by the term > signing > > Jim > > >> -----Original Message----- >> From: John Bradley [mailto:[email protected]] >> Sent: Tuesday, November 06, 2012 10:50 AM >> To: Dick Hardt >> Cc: Jim Schaad; 'Mike Jones'; [email protected] >> Subject: Re: [jose] encrypting AND signing a token >> >> I should also note that with symmetric keys, the alg option of A128KW with >> an enc of A128CBC+HS256 effectively gives you signing and encryption in a >> single JWE. >> >> That doesn't solve the asymmetric signing case, but may work for some >> people . >> >> John B. >> On 2012-11-06, at 10:37 AM, John Bradley <[email protected]> wrote: >> >>> SAML performs this as separate operations. >>> >>> Now in some cases the assertion is signed then encrypted and then the >> message signed to deal with the AESCBC padding oracle attack. >>> >>> There is non technical issue around the use of qualified signatures in > cases >> where non repudiation is required. >>> Signing a encrypted object has different connotations than signing a >> unencrypted one. >>> >>> I don't know what the status of a combined operation would be. It is >> probably not relevant to your use case. >>> >>> At IETF #83 I presented including ECDH-SS as an encryption option as it >> provides sender verification. >>> I think that would answer your use case, depending on how you feel about >> EC. >>> >>> The work group rejected adding that algorithm at the time on the grounds >> that it is not used in places where it is supported. >>> ECDH-ES is defined and is considered more secure than ECDH-SS mostly >> because it is harder to get wrong. >>> >>> I am not recommending revisiting the issue, but it would be a way to >> address the composite use case. >>> >>> Despite being a Canadian I am not shilling for certicom. Just saying. >>> >>> John B. >>> On 2012-11-04, at 2:55 PM, Dick Hardt <[email protected]> wrote: >>> >>>> Thanks Jim. An interesting historical reference. >>>> >>>> In my use case, who signed or who the token is for is not a secret. The >> payload needs to be kept a secret. >>>> >>>> Does no one sign and encrypt SAML tokens? >>>> Is this not a common use case? >>>> >>>> If it does need to be solved, it would seem to me that a standards body >> would be the place to have lots of eyes look at how to sign and encrypt a >> token so that people do not do naive sign and encrypt. >>>> >>>> Q: does anyone else need to sign and encrypt? >>>> >>>> -- Dick >>>> >>>> On Nov 4, 2012, at 10:24 AM, "Jim Schaad" <[email protected]> >> wrote: >>>> >>>>> <personal> >>>>> >>>>> I would note that the original PKCS#7 specifications had a mode that >>>>> provided a similar sign and encrypt as a single operation mode. >>>>> When the >>>>> PKCS#7 specifications where adopted by the IETF as part of the CMS >>>>> work, this mode was discussed and very deliberately dropped because >>>>> of numerous security problems that had been found. These included >>>>> (but are not limited >>>>> to) the fact that it was signed or who signed it was sometimes a >>>>> security leak. Also there were attacks where the signed and >>>>> encrypted mode could be converted to just an encrypted mode. >>>>> >>>>> I would think that there would be a need for a very detailed >>>>> security analysis that we are not prepared to do in order to support >>>>> a signed and encrypted mode. >>>>> >>>>> Jim >>>>> >>>>> >>>>>> -----Original Message----- >>>>>> From: [email protected] [mailto:[email protected]] On >>>>>> Behalf Of Dick Hardt >>>>>> Sent: Friday, November 02, 2012 12:30 PM >>>>>> To: Mike Jones >>>>>> Cc: [email protected] >>>>>> Subject: Re: [jose] encrypting AND signing a token >>>>>> >>>>>> Not only is my original token increasing in size by 4/3, I am also >>>>>> adding another header, payload and signature. >>>>>> >>>>>> One of the objectives of JWT was to enabled compact tokens. It >>>>>> would seem that we should be able to support both signing and >>>>>> encryption of the same token. >>>>>> >>>>>> All the encryption use cases I can think of involving asymmetric >>>>>> keys >>>>> would >>>>>> also require signing with the senders private key. >>>>>> >>>>>> My suggestion is to be explicit in what the algorithm etc. is used > for: >>>>>> >>>>>> Rather than "alg" and "enc", we have: >>>>>> >>>>>> "algs" - algorithm for token signing "algk" - algorithm for content >>>>>> management key encryption "alge" - >>>>> algorithm >>>>>> for payload encryption >>>>>> >>>>>> Similiarly, >>>>>> >>>>>> "kids" - key id for signing >>>>>> "kidk" - key id for content managment key encryption >>>>>> >>>>>> We could probably make these three or even two letter codes if you >>>>>> want to save a couple bytes. >>>>>> >>>>>> -- Dick >>>>>> >>>>>> On Nov 2, 2012, at 8:46 AM, Mike Jones >>>>>> <[email protected]> >>>>>> wrote: >>>>>> >>>>>>> The way you put it brings one straightforward solution to mind. >>>>>>> Solve >>>>> 1-3 >>>>>> with a JWE. Solve 4-5 by signing the JWE as a JWS payload. Done. >>>>>>> >>>>>>> I do understand that the 4/3 space blowup-of double base64url >>>>>>> encoding >>>>>> the JWE motivates your earlier proposal about nested signing. (See >>>>>> Dick's >>>>>> 10/29/12 message "[jose] signing an existing JWT".) I also >>>>>> understand >>>>> that if >>>>>> you could do integrity with the asymmetric signature then the >>>>>> integrity provided by the JWE itself may be redundant. I don't >>>>>> have a specific >>>>> proposal >>>>>> on how to do that. >>>>>>> >>>>>>> -- Mike >>>>>>> >>>>>>> -----Original Message----- >>>>>>> From: [email protected] [mailto:[email protected]] On >>>>>>> Behalf Of Dick Hardt >>>>>>> Sent: Friday, November 02, 2012 8:22 AM >>>>>>> To: [email protected] >>>>>>> Subject: [jose] encrypting AND signing a token >>>>>>> >>>>>>> I am trying to figure out how to implement JWT/JWS/JWE to solve a >>>>>>> real >>>>>> world problem. >>>>>>> >>>>>>> 1) Bob sends a token to Charlie via Alice. (Alice gets token from >>>>>>> Bob and then Alice gives token to Charlie) >>>>>>> 2) Alice must be prevented from reading the token. (token needs to >>>>>>> be >>>>>>> encrypted) >>>>>>> 3) Bob and Charlie can share a symmetric key. >>>>>>> >>>>>>> I can solve this with JWE. >>>>>>> >>>>>>> Now let's add another condition. >>>>>>> >>>>>>> 4) Charlie wants non-repuditation that Bob created the token. >>>>>>> 5) Bob has a private key and a public key >>>>>>> >>>>>>> I don't see how to do this using JWE. It seems I have to sign the >>>>>>> same >>>>> token >>>>>> I had previously with JWS. This seems inefficient since I should be >>>>>> able >>>>> to >>>>>> replace the JWE integrity computation done with the symmetric key >>>>>> with the private key -- but the "alg" parameter is the same in both >>>>>> encrypting and signing. >>>>>>> >>>>>>> Now let's expand this to replacing the symmetric key with a >>>>> public/private >>>>>> key pair for encryption. Bob encrypts with Charlies public key and >>>>>> signs >>>>> with >>>>>> Bob's private key (we also need to make sure we are not doing naive >>>>>> encryption and signing here, would be a really useful to specify >>>>>> what >>>>> needs >>>>>> to be done there). Now we need to have parameters for both >>>>>> public/private key pairs in the header. >>>>>>> >>>>>>> Am I missing something here? >>>>>>> >>>>>>> Seems like we can do this if we change the header parameters to >>>>>>> specify >>>>> if >>>>>> they ("alg", "kid", et.c) are for token signing, payload encryption >>>>>> or >>>>> content >>>>>> key encryption. >>>>>>> >>>>>>> -- Dick >>>>>>> >>>>>>> >>>>>>> _______________________________________________ >>>>>>> jose mailing list >>>>>>> [email protected] >>>>>>> https://www.ietf.org/mailman/listinfo/jose >>>>>> >>>>>> _______________________________________________ >>>>>> jose mailing list >>>>>> [email protected] >>>>>> https://www.ietf.org/mailman/listinfo/jose >>>>> >>>> >>>> _______________________________________________ >>>> jose mailing list >>>> [email protected] >>>> https://www.ietf.org/mailman/listinfo/jose >>> > > _______________________________________________ > jose mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/jose _______________________________________________ jose mailing list [email protected] https://www.ietf.org/mailman/listinfo/jose
