RPX Signature

Presented at XML Signatures WG Face-to-Face meeting 21 Jan 2000.

Outline

• Background
• Status
• Design Principles
  • About the basic requirements and principles for the design of the RPX Signature component
• Applications
  • Applications using the component
• Design Architecture
• Demonstration
• Experiences
• Open Issues

Background

• Public Key Infrastructure is being deployed widely
• The Finnish Population Register Centre is issuing Smart Cards for every Citizen
• There are commercial CAs in operation

• B2B applications are being developed based on XML technologies
• A digital signature syntax in XML is natural
• Secure information sharing and transactions are essential for B2B eBusiness

Status

• Currently based on the 1999/11 Working Draft
• First implementation is ready
• Is being used in some applications
• Collection of experience and further requirements
• Licensing is possible (model under work)

Design Principles

• The applications are Web based
• The client is a Web browser
  • Signatures are created in the browser
  • The component needs to be accessible from an HTML page using scripting
• Signatures are verified on a Web server

• Win32, Microsoft CryptoAPI, Internet Explorer

Design Principles (contd.)

• The component uses X.509v3 certificates and key-pairs (digital identities) for signature
• The user is allowed to make a choice of which digital identity to use for signature

• "What you see is what you sign"
  • XML data to be signed must be visible to the user
  • The RPX Signature component is the only trusted module, other code and data is visible on the HTML page for reference

Design Principles (contd.)

• The component only verifies the technical correctness of the signature
• It is in the application domain to verify that correct keys and valid certificates were used for the signature
  • ...or is it?

Design Architecture

• COM (or ActiveX) technology
  • The component is implemented in C++ as an ActiveX component
  • Available for Internet Explorer clients and on the server for any COM enabled platform
• Microsoft CryptoAPI
  • Used for crypto algorithms and Smart Card support
• MSXML
  • Used for XML processing

Applications

• Digitally signing on-line orders, reservations and other electronic transactions
  • How to specify what the fields of a transaction represent?
  • The application needs to refer to a specification that specifies the content of the fields
  • The reference should be included in the signature object

Applications (contd.)

• Using a forms application the user fills in form data using a user interface that is specified by a form template
• Digitally signing the content of forms
  • How to specify what form template was used to compose the content?
  • A reference to a form template should be included in the signature object

Applications (contd.)

• A gateway could act as a transport for signed XML messages, and would only allow through messages with a valid signature
• A front-end could be implemented for a "legacy" application, the front-end would only run transactions of valid XML signed messages

Demonstration

• E-Shop
  • On-line shopping application
  • Add items to a shopping basket
  • Make a signed order
  • Browse orders
• XML Forms
  • Fill in a form
  • Save the form and sign the content in XML format
  • Browse signed forms

Experiences

• The specification seems rather complex, does it need to be?

• Verifying signatures is by far the most difficult item
• XML Signature syntax allows rather complex signature objects to be created
  • How does an application find that a specific signature object meets all of the application’s requirements?

Open Issues

• What is XML Signature relation to Time Stamping Authorities (TSA)?
  • Should the specification include a timestamp element?
• Time Stamping is essential for long-term digital signature verification
  • Signed documents
  • Stored transactions (reference, later verification)

• Does the signature element support multiple signers?

• The canonicalization method used by the component is currently non-standard
• KeyInfo element encoding