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How to generate keys with the Web Cryptography API

I have been playing around with the Web Cryptography API a lot lately.  My most recent post was about getRandomValues().  I wanted to take a moment to investigate two more methods: generateKey() and exportKey().  The generation of a good cryptographic key is fairly fundamental.  I wrote up a short demo app, to demonstrate how the two functions work.

The code outputs to the console, so make sure to have Firebug open when you run the app.  Also, keep in mind that the Web Cryptography API is not fully supported in every browser, so not all of the functions in this demo will work everywhere.  I added in a description box for the crypto algorithms, so you can see the details of each one.

Have any questions? Feel free to drop a comment, below.

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Generating random numbers with the Web Cryptography API

The W3C has been working on a Web Cryptography API for a while, now.  The current version (11 December 2014) is their “Candidate Recommendation”.  As such, I would not necessarily consider it fully ready for primetime but that does not mean that we can not play around with it a bit.  I figured that today, we should take a check out getRandomValues().

According to MDN, “To guarantee enough performance, implementations are not using a truly random number generator, but they are using a pseudo-random number generator seeded with a value with enough entropy.”  You do not want to use this method to generate encryption keys (especially since generateKey() is available within the same API).  I think that this method is more foundational than anything.  It is just meant to be part of the plumbing.

Like usual, you can find the code behind my example here or check out the final result here.

Have some thoughts? Drop a comment below.


How to use FileReader() to generate data URLs

These days, the lines between the web and the local environment can be very blurry.  There is a web API called FileReader() that nicely adds to that blurriness.  It lets you asynchronously read the contents of a file on the user’s computer.  I am going to show you one way of using it.



So, what am I doing, here?  There is an input tag that is set up to accept images.  It triggers openFile() onChange.  The openFile() function looks at the first (and only) file supplied and reads it as a data URL.  The function then changes the innerHTML of the “TheImageContents” div to contain an img tag that uses the data URL as the source.

The code behind this demo is available on jsFiddle and Github Gist or you could just test the final result on jsFiddle.

The Lonesome Gods Paperback

Joe’s New “Life Hack”: Getting Rid of One Thing Per Day

Anybody who knows me well enough knows that I am a bit of a packrat.  I have been trying to work on that.  I think I have settled on a good plan.  I am going to get rid of one thing per day.  “Get rid” could mean donating, selling, or simply tossing.  This plan does not mean that I am going to be visiting the Goodwill every day.  I can batch this.  I am going to try to stick to it, though. Continue reading


Coworking in Milwaukee

As you may know, I have recently joined the ranks of the remote knowledge worker.  When Quality Matters hired me, I made the decision to get an office outside of the house.  Since QM does not reimburse for office space, my budget was limited.  I decided that it made sense to aim for a solution within the $100-$150 per month price range.  After a brief session of searching Duck Duck Go for options, I identified six potential solutions. Continue reading