Signcryption? http://www.signcryption.org/standards/
Mike Scott ________________________________________ From: [email protected] [[email protected]] on behalf of Jim Schaad [[email protected]] Sent: 04 November 2012 20:51 To: 'Dick Hardt' Cc: 'Mike Jones'; [email protected] Subject: Re: [jose] encrypting AND signing a token > -----Original Message----- > From: Dick Hardt [mailto:[email protected]] > Sent: Sunday, November 04, 2012 2:56 PM > To: Jim Schaad > Cc: 'Dick Hardt'; 'Mike Jones'; [email protected] > Subject: Re: [jose] encrypting AND signing a token > > 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 An interesting historical reference.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? Everything I have seen does this as independent operations. Jim > > 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
