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@@ -39,6 +39,49 @@ an untrusted device. You would in any case not be able to decrypt previously
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received OMEMO messages, due to the Signal Protocol's forward secrecy and the
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fact that you don't have a pre-existing session.
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+Security considerations for browser-based crypto
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+------------------------------------------------
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+
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+Crypto apps deployed via regular web hosting can be described as relying on
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+"host-based" security.
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+
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+Host-based security services require you to trust the host every time you access
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+it, whereas with installable desktop software you trust the host when you
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+download/install the software (and whenever it gets updated).
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+
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+The dynamic nature of "host-based" systems makes it impractical for security
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+researchers to do security audits because the hosted code can change at any
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+time.
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+
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+In such a setup you need to fully trust the host that serves you the JavaScript code.
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+
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+The host that serves the JavaScript code is not necessarily the same host that
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+stores and procesess your chat messages. So using OMEMO can still protect your
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+messages from snooping on the XMPP server where they're stored encrypted.
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+
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+In other words, you do have to trust the webserver that hosts Converse for you,
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+but you don't necessarily have to trust the XMPP server (if it's on a different host),
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+because it never gets hold of your private key.
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+
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+One way to improve this situation is to host Converse yourself, especially if
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+you host it locally on your own machine. If you're not able to do that, then
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+at least make sure you use a reputable host that serves files over HTTPS and
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+that set `CSP <https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy>`_
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+headers.
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+
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+Due to these reasons, it's NOT a good idea to use encrypted messaging with a
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+browser-based solution in life-threatening situations.
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+
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+Security can be increased by using an installable app (like one based on `Electron <https://electronjs.org/>`_)
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+with a strict Content Security Policy.
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+
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+Look out for an Electron based version of Converse coming in the following months.
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+
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+For further reading on the challenges of web-based crypto, take a look at these
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+articles:
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+
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+* `What's wrong with webcrypto? <https://tonyarcieri.com/whats-wrong-with-webcrypto>`_
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+* `Heartbleed and JavaScript crypto <https://tankredhase.com/2014/04/13/heartbleed-and-javascript-crypto/>`_
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Notifications
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=============
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JC Brand