A couple of years ago I was enamored with a clever password manager that pointed the way toward an ideal solution. It was really just a bookmarklet — a small chunk of JavaScript code — that used a simple method to produce a unique and strong password for the website you were visiting. The method was to combine a passphrase that you could remember with the domain name of the site, using a one-way cryptographic hash, in order to produce a strong password that would be unique to the site — and that you’d otherwise never be able to remember.

It wasn’t perfect. Sometimes the passwords it generated wouldn’t meet a site’s requirements. And sometimes the login domain name would vary, which broke the scheme. But it introduced me to two powerful — and related — ideas. JavaScript could turn your browser into a programmable cryptographic engine. And that engine could be used to implement protocols that relied on cryptography but transmitted no secrets over the wire.

To my way of thinking, that’s a killer combination. For years I’ve been using Bruce Schneier’s Password Safe, a Windows program that keeps my passwords in an encrypted store. There are many such programs, another example being 1Password for the Mac. This kind of app lives on your computer and talks to a local data store. That means it’s cumbersome to move the app and your data from one of your machines to another. And you can’t use it online, say from a public machine at the library or a friend’s computer.

Imagine a web application that would encrypt your credentials and store them in the cloud. It would deliver that encrypted store to any browser you happen to be using, along with a JavaScript engine that could decrypt it, display your credentials, and even use them to automatically log you onto any of your password-protected services. You’d trust it because its cryptographic code would be available for security pros to validate.

I’ve wanted this solution for a long time. Now I have it: Clipperz. My guest for this week’s Innovators show is Marco Barulli, founder and CEO of Clipperz, which he describes as a zero-knowledge web application. What Clipperz has zero knowledge of is you and your data. It just connects you with your data, on terms that you control, in a way that reminds me of Peter Wayner’s concept of translucent databases.

Clipperz is immediately useful to all of us who struggle to manage our growing collections of online credentials, But it’s also a great example of an important design principle. We reflexively build services that identity users and retain all kinds of information about them. Often we need such knowledge, but it’s a liability for the operators of services that store it, and a risk for users of those services. If it’s feasible not to know, we can embrace that constraint and achieve powerful effects.