January 9th 2013
PolyCrypt contains most or all of the functions in the current WebCrypto draft, except under the window.polycrypt namespace instead of window.crypto. This is because some browsers like Chrome already have window.crypto despite only containing the random number generation method.
Just like the browser crypto API will be, PolyCrypt is asynchronous, taking advantage of Web Workers to perform expensive computations. PolyCrpypt also lives in another origin via an invisible iframe on the page, communicating with the main page via postMessage, which is an interesting decision. You can find out more about how it works on their detailed documentation page.
As web applications become more complex, we will need good cryptography in the browser, as secure as we can make it. The WebCrypto API promises to solve some of our problems, and PolyCrypt is a good way to get started and get familiar with the API while browsers dillydally.