SQL Azure “Vidalia”: Practical translucency

Ever since Peter Wayner introduced me to the idea of a translucent database I’ve been thinking about the implications of this powerful idea. In a nutshell, the data in a translucent database service is opaque to the operator of the service, and visible only to sets of users who establish trust relationships. My 2002 review of Peter’s book summarizes his babysitter example:

Imagine a web service that enables parents to find available babysitters. A compromise would disastrously reveal vulnerable households where parents are absent and teenage girls are present. Translucency, in this case, means encrypting sensitive data (identities of parents, identities and schedules of babysitters) so that it is hidden even from the database itself, while yet enabling the two parties (parents, babysitters) to rendezvous.

Fast forwarding to 2009, here’s a current headline from InfoWorld: Microsoft adds access controls for SQL Azure online database. The article doesn’t say so, but this is database translucency in action.

The 2009 version of the babysitter example appears at 37:45 in this PDC session, where Dave Campbell and Rahul Auradkur discuss, and also show, a translucent pharmaceutical reagent marketplace. Dave Campbell spells out the scenario:

Pharma companies see reagents as being pre-competitive. They don’t compete at that level, and they’re willing to sell these reagents to one another, as long nobody can see what’s being bought and sold. That’s the controlled trust we need to set up.

The trick is accomplished by means of encryption and careful separation of concerns. Access policies are isolated from data storage, capable of federation, and auditable by trusted intermediaries.

This is exciting new territory. Historically, we’ve always assumed that the operator of an online information system has complete access to the data in that service. Translucency turns that assumption on its head, and leads to entirely new service design patterns. To implement those patterns requires more than just a database in the cloud. You also need a coordinated suite of supporting services for identity, access control, auditing, and more. Azure, as it becomes one provider of such services, will help make translucency a practical reality.