Stuff Yaron Finds Interesting

Technology, Politics, Food, Finance, etc.

Articles about SOA, the Web, Utility Computing, etc.

Derived keys and per user encryption in the cloud

I use a program called ESPlanner to help with planning our insurance and retirement portfolio. ESPlanner wants to move to the cloud. Below I explore who I imagine would want to attack a site like ESPlanner and what sort of things cloud services like ESPlanner can do to frustrate their attackers. I especially look at using derived keys and per user encryption to potentially slow down attacks. But in the end, I'm uncomfortable with the legal protections afforded me as a service user in the US and so I really want a download version of ESPlanner.
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User IDs – managing the mark of Cain

Facebook's latest privacy debacle was driven by their failure to properly manage user IDs. This is not a new problem area and as the EFF points out, Facebook has done this before. So while I don't know if Facebook will be interested in this post, those who care about protecting their user's privacy in an age of data sharing may want to have a look at the threats and defenses needed to share user IDs across sites. Securing user IDs isn't easy.

[Update 10/22/2010: Changed the title and intro and added three new sections at the end.]

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Bearer Tokens, Discovery and OAuth 2.0

Part of my day job is working on adding discovery to OAuth 2.0. This article provides a summary of some of that work. So I was more than a little concerned when I saw a blog article from Eran Hammer-Lahav, the editor of OAuth 2.0, asserting that OAuth 2.0 couldn't support secure discovery. Very worried that something was terribly wrong I carefully read Eran's article. I summarize below what I believe his concerns are and explain how I believe those concerns would be addressed by extensions to OAuth 2.0 to support discovery. I also explain how Eran's article helped me find a flaw in my own proposal and how I propose fixing that flaw.

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Building full delegation in OAuth – This time in English

OAuth enables a very simple type of delegation, a user can delegate permissions between two services that they have accounts on. In other words, OAuth lets a user delegate permission to themself. But full delegation allows arbitrary users of arbitrary services to give permissions to each other. In this article I summarize the two key extensions to OAuth needed to enable it to do full delegation. The first is ’on behalf of’ (e.g. a service saying ”I am making this request on behalf of user X”) and the second is a very simple directory service. The rest of the article tries to use something like plain English to explain how these features could work in OAuth. Read More

Thoughts on updating finger services

Having a finger service as a directory to find information about users and services appears to be absolutely necessary if ad-hoc information sharing between people and services is to be possible. But just having a way to finger a person or service is less than 1/2 the battle. The real challenge is making it possible for services to update their user’s finger information in an ad-hoc manner. I explore the issues around dynamic finger update in this article. Read More

Thoughts on building a finger service

Those folks of a certain age will remember the finger command/protocol which allowed one to look up information about a person based just on their login identifier. This command was extremely useful even if it had some troubling security and privacy implications. Efforts are underway to create a Web Finger but for reasons I’ve previously discussed I think the underlying technologies for those efforts are sub-optimal. So in this article I propose what I think is a much simpler approach. My motivation for caring is that I think having a finger service will make permissioning systems much more useful (see here and here). Read More

The outline of a profile for granting permissions using OAuth WRAP

In a previous article I talked about adding a profile to OAuth WRAP that would enable users to ask for or grant permissions to each other. In this article I show that an OAuth WRAP profile to handle granting permissions only needs two request/response pairs. I then show that an OAuth WRAP profile to handle asking for permissions only needs one additional exchange. Read More

Open permissions matter for an open web

The key to an open social web is permissions. There is data we don’t want to share and data we do want to share, permissions let us create the appropriate barriers. Closed networks like Facebook have reasonably rich permission infrastructures but what about open networks? How should Google and Microsoft enable document sharing across Google Docs and Sharepoint Online? Sure WebDAV can handle the actual mechanics of listing out documents, editing, etc. But how do the permissions get put into place in an open manner directly between users of the two services? This is a hole in the standards infrastructure and it’s time to fill it. Read More

The CAP theorem and modern data centers – for now, choose consistency!

The dominance of the commodity machine model for data centers is so complete that one forgets that there was ever any other viable choice. But IBM, for one, is still selling lots of mainframes. Nevertheless the world I live in is built on top of data centers that contain a lot of commodity class machines. These machines have a nasty habit of failing on a fairly regular basis. So when I think about the CAP theorem I think about it in the context of a data center filled with a bunch of not completely reliable boxes.

In that case partition tolerance (which, as I explain below, ends up meaning tolerance of machine failure) is a requirement. So in designing frameworks for the data centers I work with the CAP theorem makes me choose between exactly two choices - do I want consistency or availability?

My belief is that for the vast majority of developers, at least for the immediate future, they need to choose consistency.

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