The Evolution of Secure Messaging: Exploring Encrypted and Decentralized Communication

Encrypted messaging applications are entering a new phase of development.

Key Takeaways

Next-Gen Messaging: Applications like Session are shifting towards decentralized messaging while maintaining E2EE to enhance privacy threats.
Secure Message Handling: Session uses a decentralized network to ensure private communication, relying on public key identities instead of personal information like phone numbers.
Notification Choices: Users balance between privacy and convenience with notification settings (Slow Mode vs. Fast Mode).
Government and Transparency: Recent changes in governance and transparency reporting showcase how user data is managed and protected despite government requests.
Quantum Resistance: Innovations are underway to ensure messaging security against future quantum computing threats.

Apps like WhatsApp, iMessage, and Signal have established end-to-end encryption (E2EE) as a standard feature for secure communication. However, many of these platforms still rely on phone numbers, centralized servers, and accumulate significant metadata, including details about your contacts, communication times, IP addresses, and the devices used.

Vitalik Buterin recently emphasized a new direction for secure messaging through his posts on X and donations, advocating for permissionless account creation that eliminates the need for phone numbers or Know Your Customer (KYC) protocols, along with enhanced metadata privacy. He drew attention to Session and SimpleX as platforms pushing towards these privacy-centric goals, even donating 128 Ether to each service to support their efforts.

Image of messaging decentralization

How Session Stores Your Messages

Session operates on the principle of public key identities. When registering, users generate a key pair locally and derive a Session ID without needing a phone number or email.

Messages are routed through a network of service nodes that utilize onion routing, meaning no single node has visibility into both the sender and recipient. Users can view the path taken by their messages in the settings. If you're offline, messages are stored in small clusters called "swarms," where each Session ID is linked to a specific group, keeping messages encrypted until they're retrieved by the client.

Historically, messages maintained a default lifespan of around two weeks in the swarm; beyond that, only what remains in your devices is accessible. Session does keep a local database of chats and attachments, allowing users to scroll through conversations from months or even years ago. While the app's initial download size ranges from 60 to 80 MB, it expands as media is sent, thumbnails are cached, and chat history accumulates. Users can manage storage by deleting conversations, using disappearing messages, or clearing media. Remember, if you can still see it, it continues to exist somewhere on your device.

Image of message storage

Notifications: Privacy vs. User Experience

Notifications illustrate the trade-offs between privacy and user experience (UX).

On iOS, Session has introduced two notification modes:

Slow Mode: This mode conducts background polling, causing the app to periodically check for new messages via its own network. While more private, this method can be slower and less reliable, especially if your operating system aggressively manages background activities.
Fast Mode: This option leverages push notifications via Apple Push Notification Service on iOS and similar systems on Android for real-time alerts.

The Fast Mode option poses some privacy concerns. By using it, your device's IP address and push token are exposed to an Apple-controlled push server, necessitating that your Session Account ID and push token be shared with a Session-run push server for routing notifications.

Despite these privacy compromises, the message contents remain secured with E2EE, and Session asserts that neither Apple nor Google can see the identities of contacts or the precise timing of messages beyond what is required for functionality.

For those prioritizing privacy, Slow Mode is available but comes with a delay in receiving notifications.

Governance, Transparency, and Information Requests

Session’s governance model has undergone significant changes.

Initially managed by the Australian nonprofit Oxen Privacy Tech Foundation (OPTF), the stewardship of the project transitioned to the Session Technology Foundation (STF) in late 2024. The final transparency report from OPTF covers Q4 2024, and the STF manages future requests and publishes those updates.

Session’s documentation details how it handles information requests:

Due to the decentralized nature and E2EE of the platform, the foundation does not have special access to user messages or keys.
The STF routinely publishes transparency reports that summarize how law enforcement requests are handled.

This transparency serves as a public record detailing when authorities inquire about user data, outlining what is shared and how Session responds.

So, what can they provide?

Possibly: Logs from website and server activities that they directly control, which may be subject to Swiss law and any related international obligations.
Definitely not: Decrypted messages or master keys for user chats, provided that the implementation adheres to the described protocol.

Switzerland's regulatory environment is relatively lenient regarding transparency, making voluntary reports and data restrictions crucial.

While decentralization does not entirely shield users from government inquiries, it restricts the nature of information that can be provided.

Did you know? When police infiltrated the EncroChat encrypted network, they intercepted over 115 million criminal communications from approximately 60,000 users, resulting in over 6,500 arrests and nearly 900 million euros in seized assets globally.

Quantum Resistance, Voice Calls, and Ongoing Beta Status

One pressing concern is the risk of present-day data being decrypted in the future as quantum computers evolve.

To address this, Session launched a comprehensive redesign of its protocol. In a recent announcement, the team introduced Session Protocol v2, focusing on:

Perfect Forward Secrecy: Utilizing ephemeral keys that renew with each session.
Post-Quantum Key Exchange: Employing ML-KEM (formerly CRYSTALS-Kyber), a NIST-standardized Key Encapsulation Mechanism (KEM) being integrated into systems like Signal's PQXDH and Apple's PQ3.

Regarding quantum resistance, Session is not fully equipped yet. While it still employs traditional elliptic curve cryptography, improvements are anticipated as Protocol v2 progresses. This roadmap does hint at incorporating hybrid post-quantum methodologies, but until these changes are fully implemented, users should remain cautious and assume standard E2EE security levels.

Calls, both voice and video, are currently a beta feature that users must opt into. At this stage, they utilize peer-to-peer WebRTC, which exposes the user's IP address to the other party and to Session-operated STUN or TURN servers for signal relay and media transfer. More secure onion-routed calls over Lokinet are planned for future implementation but are not yet standard.

Session's blog and FAQs clearly advise that users in sensitive scenarios might want to avoid enabling calls at this time, indicating how challenging it is to merge low-latency communication with onion routing and robust anonymity.

Understanding the Impact of Decentralization

Session exemplifies both the potential and limitations of decentralized messaging platforms.

On the positive side:

Users can create accounts without providing a phone number or email, which aligns with Buterin’s vision for open access.
Messages navigate through a multi-node onion-routed network, significantly limiting the metadata seen by any single operator or retained in logs.
The transition to Swiss governance, combined with open-source clients and transparency reporting, increases scrutiny over codebase and infrastructure enhancements.

However, decentralization is not without its challenges:

Local storage on devices poses a risk if the device is compromised or seized.
The Fast Mode notifications and WebRTC calls can leak IP-level metadata to infrastructure providers, even without accessing plaintext messages.
Post-quantum measures are still a work in progress until Protocol v2 is fully released and adopted.

If you’re considering using Session, it's advisable to start with Slow Mode to protect your metadata privacy at the expense of instant notifications. Implement features like disappearing messages and periodically remove unused chats and media from your device. When it comes to calls, if linking a Session ID to an IP address poses a risk, it may be better to disable voice and video features until the call infrastructure is more secure.

In conclusion, E2EE alone is no longer adequate for privacy. As pressures from governments increase and quantum computing threats emerge, the focus is shifting to decentralization, minimizing metadata collection, and future-proofing systems against quantum risks, all of which are now fundamental aspects of secure messaging. Session is one of several projects grappling with these complexities, each with its distinct trade-offs, strengths, and weaknesses.