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CoverDrop

lastmod 2025-06-11created 2025-06-111 edits

A secure messaging system for news reader apps

About

  • An open-source secure messaging solution that lets news reader app users and journalists communicate safely while preserving each other's anonymity and deniability
  • Every user device generates random encrypted traffic, so even when messages are exchanged, it is indistinguishable on the network from ordinary news reading
  • Messages are double-encrypted and handled at an identical size and frequency, leaving no evidence even if a device is seized
  • Consists of a complete end-to-end structure, including a mobile app, cloud API, secure server, and desktop client for journalists
  • Transparent open-source development, strong cryptography, and specialized features optimized for news organizations' needs are its advantages over existing projects

How it works

  • Every instance of the news app periodically exchanges small encrypted data ("cover messages") with the server
  • Real tips (source messages) are encrypted and sent exactly like ordinary cover messages. They are indistinguishable on the network
  • All messages are handled at the same size and interval, and are sent to and processed through a Kinesis stream
  • The server performs the first layer of decryption and identifies real messages, which are delivered to the journalist client as a dead drop. Padding keeps the dead drop size uniform
  • Journalists can perform final decryption only on messages encrypted with their own public key
  • The message store stays encrypted at all times, so even if a device is seized, it cannot be proven whether a conversation actually took place
  • When a journalist replies, encrypted communication and key exchange take place in a similar way

More detailed design and algorithm structure can be found in the white paper co-written with the University of Cambridge Department of Computer Science

Security policy

  • CoverDrop's security is the top priority
  • Acknowledges that perfect security is impossible; reports from security researchers are welcome
  • Issues related to message confidentiality, integrity, network anonymity, and deniable encryption are areas of ongoing improvement
  • Side-channel issues caused by other elements within the integrated news app are also being actively improved

Caveats on using cryptographic software

  • CoverDrop includes cryptographic software
  • Must comply with each country's laws on the import, use, and re-export of cryptography
  • U.S. Department of Commerce BIS classification: ECCN 5D002.C.1 (software containing asymmetric cryptography)
  • This open-source distribution falls under the export exception provision (TSU, §740.13)

See also

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