How is Signal.org Encrypted By Default?

How is Signal EncryptedByDefault you may ask?

GPT-4 Prompted and remixed by =this.owner-group

Signal is a messaging app known for its focus on privacy and security. Signal, both as an organization (Signal.org) and through its messaging app (the Signal app), prioritizes user privacy and security through state-of-the-art end-to-end encryption protocols, ensuring that messages are readable only by the sender and recipient, not even by Signal itself. This encryption ensures that users’ messages, calls, and media are secured from eavesdropping or interception. This article explores the technology behind Signal’s encryption, emphasizing its default encryption mechanisms.

The Signal Protocol

Signal uses its own Signal Protocol (formerly known as the ¹Axolotl Protocol) to implement E2EE. The Signal Protocol is considered one of the most advanced cryptographic protocols for secure communication and has been implemented in other messaging services because of its robust security features.

Key Components of the Signal Protocol:

• End-to-End Encryption E2EE: Signal’s use of end-to-end encryption E2EE means that messages are encrypted on the sender’s device and can only be decrypted by the recipient’s device. This process ensures that no third parties, including Signal’s servers, can access the contents of the communication.

• Double Ratchet Algorithm: This algorithm combines a symmetric-key ratchet and a Diffie-Hellman ratchet to ensure that each message has a unique encryption key. The triple Diffie-Hellman (3-DH) handshake is used to establish a secure session between two parties. It combines public keys from the prekey bundle with the initiator’s keys to create a shared secret from which encryption keys are derived. This handshake ensures that the session is securely encrypted from the start. This significantly enhances security, making it extremely difficult for attackers to decrypt messages even if they obtain a key.

• Prekeys: Signal’s use of prekeys allows users to establish secure communication channels even when one of the parties is offline. This is achieved by storing a small number of one-time prekeys on Signal’s servers, which can be used to initiate secure sessions.

• Sealed Sender: To further enhance privacy, Signal introduced “Sealed Sender,” a feature that encrypts metadata, including the sender’s identity. This means that not even Signal can ascertain who is messaging whom, providing an additional layer of privacy.

• Disappearing Messages: Messages can be set to disappear after a certain period, enhancing privacy.

• View Once Media: This feature allows sending photos and videos that can only be viewed once by the recipient before being permanently deleted.

Encryption in Practice

When a user sends a message or makes a call:

1. Initiation: The sender’s app uses the recipient’s public keys (obtained from Signal’s servers) to initiate an encrypted session.
2. Encryption: The Signal Protocol encrypts the message or call using a combination of the recipient’s public key and the sender’s private key, ensuring that only the recipient’s private key can decrypt the message.
3. Transmission: The encrypted message is transmitted through Signal’s servers without revealing its contents.
4. Decryption: The recipient’s app uses their private key to decrypt the message, rendering it readable or listenable.

Conclusion

Signal’s default encryption mechanisms are simply designed to ensure that users’ communications are secure and EncryptedByDefault . By leveraging the Signal Protocol, alongside features like Sealed Sender, disappearing messages, and view once media, Signal provides a platform where privacy and security are paramount. This approach to encryption, focusing on both the technical and practical aspects, has made Signal a preferred choice for users prioritizing confidentiality and security in their digital communications.

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Perlexity.ai Source Verification of "Axolotl Protocol"

The Axolotl Protocol is a key management algorithm that was previously referred to as the Axolotl Ratchet. It was developed by Trevor Perrin and Moxie Marlinspike in 2013 and is used as part of a cryptographic protocol to provide end-to-end encryption for instant messaging[1]. The algorithm combines a cryptographic “ratchet” based on the Diffie–Hellman key exchange (DH) and a ratchet based on a key such as a hash function, hence the name Double Ratchet Algorithm[1]. It provides forward secrecy for messages and implicit renegotiation of forward keys, properties for which the protocol is named[1]. The algorithm was initially named after the critically endangered aquatic salamander axolotl, which has extraordinary self-healing capabilities[1]. In March 2016, the developers renamed the Axolotl Ratchet as the Double Ratchet Algorithm to better differentiate between the ratchet and because some had used the name Axolotl when referring to the Signal Protocol[1]. The Double Ratchet Algorithm is used in the Signal Protocol, which combines the Double Ratchet Algorithm, prekeys, and a 3-DH handshake to provide confidentiality, integrity, authentication, participant consistency, destination validation, forward secrecy, backward secrecy, causality preservation, message unlinkability, message repudiation, participation repudiation, and asynchronicity[1]. The Double Ratchet Algorithm is used in the Signal Protocol, which is used in the Signal app, WhatsApp, and other messaging apps[1][2].

Citations: [1] https://en.wikipedia.org/wiki/Double_Ratchet_Algorithm [2] https://taravancil.com/blog/axolotl-an-attempt-at-a-summary/ [3] https://github.com/wireapp/proteus [4] https://www.signal.org/blog/signal-inside-and-out/ [5] https://fantaxies.com/blogs/news/28-axolotl-safe-medications-treatments-the-complete-list

Footnotes

1. See Source Verification ↩