DARPA’s Perfect Encryption App and the Folly of Blockchains for Everything

Imagine ordering a powerful new pneumatic nail gun. You aren’t a roofer; you bought it mostly as a toy because you like power tools. The first thing you would do after unpackaging it is start looking around for things to nail and nail you would: walls, your workbench, walls, boards, and walls. You have a new toy- a new technology- and you want to use it wherever you can justify using it.

Seven years ago blockchains were invented as part of Bitcoin. For year one, almost no one knew the project existed. In year two, people learned how to make use of the currency. During year three, people started using a different blockchain, Namecoin, to hold domain name information in a system which was academically interesting but not widely used. Since then people have started trying to hold all kinds of things in blockchains: deeds, contracts, and all sorts of documents. On the outside, it sounds sensible: a censor-proof fully distributed persistent data storage system.

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Forget Apple vs FBI, Slack & Gmail already have Backdoors

Apple vs FBI should be the least of your concerns, because right now your emails, chats and files are not private, and they’re certainly not secure.

Not at home, and not at work.

If you’re like most internet-goers there’s a good chance you’re using some combination of Slack, Gmail, Dropbox or one of the many other popular message and file sharing apps on a daily basis; so why worry about Apple building backdoors into the iPhone if you’re perfectly content sharing your most sensitive messages and files through apps that already have the equivalent of built-in backdoors?

Value your privacy and security? If the answer’s yes, then you’re going to want to keep reading. And buckle up, because you’re in for a few surprises.

In this post we’re going to talk about how the communication, file sharing and file storage layers have become a huge security vulnerability for individuals and organizations of all sizes, why, and what you can do about it.

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How ClearChat Works

ClearChat is the name of our company and also the name of a stand-alone desktop (and eventually mobile) client. The client encrypts messages so that only people participating in a group can read them. Here we discuss how that works.

This is a technical overview of how ClearChat works for those who are interested in specifics. You do not need to read or understand any of this to use ClearChat correctly unless you are the admin for your company in which case you might choose to just read the section on authentication.

TL;DR  Each message is encrypted then HMAC’d with a randomly generated unique 256 bit key using AES-CTR, hereafter the “AESEphemKey”. Then, for every participant who must receive the message, the AESEphemKey is encrypted with the participant’s 512 bit secp256k1 elliptic curve public key and that encrypted AESEphemKey is added to the top of the ciphertext as a header. The whole thing is signed using ECDSA and SHA256, and then the information is sent to the server and relayed to the receiving clients. Each receiving client checks the signature, finds their header, decrypts the AESEphemKey using their private key, and then decrypts the main ciphertext using this AESEphemKey. Sending files works similarly except that files are split, compressed, encrypted, and sent in pieces to speed things up. Key authentication is taken care of by an admin at your company; if users trust the admin then they do not need to all verify each other’s keys.

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