WebSign standardization effort - Encryption considerations

A potential WebSign standards effort should IMHO not deal with explicit message encryption, as I believe this is a less generally useful "feature". It is rather the provider (your employer, your bank, your government), that sets the policies, including encryption, for a specific web application and acts accordingly.   In an off-line e-mail scenario you don't have this option and due to this, policies effectively becomes a client issue.  However, finding the proper encryption key to use is a major problem that clients should not have to deal with in a properly designed web application.  To protect contents against the web application provider's eyes seems like an odd measure, unless we are actually talking about WebMail.

Secure WebMail is though an entirely separate issue as it must conform to S/MIME rather than using XML security.  In addition, if Secure WebMail is to be used with untrusted mail providers, it requires the use of Wet Signatures (open forms), and "semi-fat" clients, as the providers MUST NOT (if message encryption is to be used), be able to "see" any clear text data, including possible attachments.  The latter means that the standard way to handle attachments today, "upload", simply is not an option.  Secure WebMail is due to those constraints, IMO another [possible] standardization effort.  Even if a Secure WebMail standardization effort indeed were launched, I would not build such a scheme for untrusted providers as the "market" for such a scheme seems limited when standard e-mail clients comes for free and already handles this scenario.  The possible use-case with public computers do not align well with encrypted content as public computers cannot be assumed to be safe for communicating truly classified or very private information, for that you should use your mobile phone or PDA, "model 2007" with built-in TPM (Trusted Platform Module) support.

Comments?

Anders Rundgren
Working for a major US computer security company but here acting as an individual