Receipt Token Profile for Web Services Eric Gravengaard Reactivity

© 2003 Reactivity slide 2 What is the problem? Signatures prove: The signed contents of the message have not been changed since it was signed Receipts prove: The signed contents of a message I sent was received by you as I sent it Example: I sign and send: Add(1, 3) I receive a signed response: 5 Is there a simple and secure way to know that Add(1, 3) = 5? Can I trust that you really checked my signature? Can I prove it?

© 2003 Reactivity slide 3 How can receipts be used? In a simple client/server request/response system: The Client Composes a request Signs the request with its private key The Server Composes a response and attaches a receipt Signs the response and receipt with its private key Both Parties Validate signatures Write logs at each step John: Please review my draft copy of a declaration of independence. Benjamin Franklin BF Ben: I received your draft. Here are some of my comments. John Hancock JH

© 2003 Reactivity slide 4 What can we prove? The secure logs prove: That a transaction occurred That our record of the transaction has not been altered The signatures prove: Server can prove that someone with the client’s private key sent the request Client can prove that someone with the server’s private key returned the response and the receipt together The receipt proves: Client can prove that someone with the sender’s private key received their request and that the response message is in response to the original request

© 2003 Reactivity slide 5 Existing uses of non-repudiation Most large business to business transactional systems implement some form of non-repudiation Example: EDI Early mechanisms were proprietary More recently: AS1/AS2 Standards (RFC #3335, Sept 2002) Web Services have no existing mechanism… …but current specifications provide some good tools: XML-Signature Web Service Security: SOAP Message Security Intermediate Roles ( )

© 2003 Reactivity slide 6 XML-Signature Provides a mechanism for specifying a signature and relevant meta-information I8U/3X26MjaTplqjQeTu1C56Elo=

© 2003 Reactivity slide 7 Web services security: receipt token profile WSS: SOAP Message Security does not provide a mechanism for receipts and secure logging WSS:RTP is Reactivity’s proposed extension to WSS that: Creates a new security token for requesting receipts Creates a new security token for receipts Defines both signed and unsigned receipts

© 2003 Reactivity slide 8 RTP receipt mechanism Provide a general purpose receipt request mechanism provides: : signed or unsigned request : UUID for tracking receipts /ReceiptRequest/ReceiptTo : how to send receipt /ReceiptRequest/SignatureRequest : what elements to be signed /ReceiptRequest/wsu:TimeStamp : when this request was made provides: : signed or unsigned receipt : same UUID as request /Receipt/SignatureResponse : signature of receipt generator /Receipt/wsu:TimeStamp : when this receipt was generated

© 2003 Reactivity slide 9 Receipt example T16:30:17Z T16:33:43Z Response Request

© 2003 Reactivity slide 10 Signed receipts Main concept: Split the into two pieces Requestor specifies a element: /SignatureRequest/ds:SignedInfo : specifies algorithms and data to be signed by receipt generator /SignatureRequest/ds:Object : allows other data to be included in the signature Responder returns a element: /SignatureResponse/ds:SignatureValue : cryptographic signature that covers the of the request /SignatureResponse/ds:KeyInfo : specifies information about the key used to generate the signature

© 2003 Reactivity slide 11 Bringing it all together: an example T08:42:00Z <wsse:BinarySecurityToken wsu:Id="#theCert“ EncodingType="Base64Binary"> MIIEZzCCA9CgAWIQEmtJZco... ABCDEFG T08:42:12Z

© 2003 Reactivity slide 12 Isn’t this defined in… Reliable Messaging WS-Policy WS-Addressing WS-Routing …maybe, but none of them offer any form of cryptographic proof of receipt

© 2003 Reactivity slide 13 Proposal The TC takes on the work of producing a receipt mechanism to be specified in a token profile, timeframe to be determined The TC accepts as an input to this profile the document submitted by Reactivity Further work to be done: Utilize message identifiers from other specifications