Documentation

About Martus' Security

Martus uses a variety of standard encryption algorithms. It uses password-based encryption (PBE) to store encrypted RSA keypairs. RSA 3072-bit keys are used in combination with AES 256-bit symmetric keys to encrypt and decrypt records while SHA digests are used to digitally sign and verify each record, and all server communications use TLS/SSL. The users’ RSA private keys are never sent to the server, which means that the server can never decrypt any user data. Record authors can choose which other Martus accounts (if any) can also read their private bulletin data. The Martus application itself (in JAR file form) is signed by the Martus developers.

Martus is built in Java and relies on Bouncy Castle, an open source collection of APIs, for its cryptography. Our ecosystem integrates with renowned anonymity tool Tor via JTor/Orchid for multi-platform desktops, and Orbot for android devices. We are currently packaging Martus for Debian and are in discussions for it to be included by default in Tails, a Debian derivative that can reduce the surface attack of any user by offering a single-state, privacy-enhancing operative system. You can read about our recent work with Tails in our post on Benetech's blog.

The various ways in which Martus uses cryptography ("crypto") include:

• Identifying a user account
• Encrypting record data
• Encrypting account/configuration of data
• Signing record data to prevent tampering
• Securing communications between client and server (and between servers)
• Safely backing up client account data in multiple locations, without a passphrase
• Verifying that martus.jar and language packs are authentic
• Verifying that downloads are authentic and unchanged