OSHI vs Signal — An Honest Comparison

Signal is the reference point for private messaging, so any serious Signal alternative has to be measured against it fairly — including where OSHI falls short. OSHI and Signal draw on the same cryptographic building blocks — modern elliptic-curve key exchange and, in OSHI's newer session format, a Double Ratchet — but they solve different problems and are at very different stages of maturity.

Signal is a mature, heavily audited, non-profit messenger with a very large user base and excellent uptime; if you want a mainstream encrypted app that "just works" and that most of your contacts can join, Signal is hard to beat. OSHI is a Swiss, MIT-licensed, open-source messenger built for people who need to communicate without a phone number, without infrastructure, and even without the internet. It adds a Bluetooth and WiFi mesh, Tor routing, a content-addressed store on its own server for large attachments, on-device AI, and an optional disguised relay transport for filtered networks. This page lays out where each app genuinely wins so you can pick the right tool.

Feature comparison: OSHI vs Signal

Where Signal genuinely wins

It would be dishonest to pretend Signal is not excellent. Signal has undergone multiple independent security audits, and its protocol is the academic and industry standard for end-to-end encryption — the same protocol is licensed by WhatsApp, Google and others. That level of scrutiny matters: the Signal Protocol has been formally analysed and battle-tested at a scale few systems ever reach.

Signal also has an enormous, cross-platform user base and solid desktop clients for Windows, macOS and Linux. Because so many people already have it, the practical privacy benefit is high — you can actually convince friends and family to switch. It is run by a non-profit foundation funded by donations rather than advertising, and its infrastructure has a long track record of reliability. If your threat model is "strong, well-understood encryption that everyone can use today," Signal is the sensible default.

Where OSHI is different

OSHI targets situations Signal was never designed for. The headline difference is no phone number: you can create an OSHI identity without handing over personally identifying information. Signal now offers usernames, but you still need a phone number to register in the first place.

The second difference is working without infrastructure. Signal needs the internet and its servers reachable. OSHI can relay encrypted messages directly between nearby devices over a Bluetooth and WiFi mesh network, hopping through intermediate phones that can never read the contents. During internet shutdowns, in remote areas, at crowded events, or after a disaster, that is the difference between communicating and going dark. OSHI layers on Tor routing and, for large attachments, falls back through its own encrypted relay to a content-addressed store on that same server — the mesh first, the server only when the mesh cannot carry it.

Finally, on iOS and Android OSHI adds an optional disguised relay transport that makes its encrypted relay traffic look like ordinary web requests — helpful against simple filtering, not a guarantee — and on-device AI for translation, correction and tone that never leaves your phone.

How the encryption compares

Signal pairs X3DH key agreement with the Double Ratchet, giving per-message forward secrecy by design. OSHI uses X25519 key exchange with AES-256-GCM in the same family, and implements a Double Ratchet — but only in its v3 session format. The older v2 format does not ratchet, and most of the OSHI installed base is still running v2. So the accurate statement is that OSHI has implemented forward secrecy, not that every OSHI conversation has it. A v3 responder bug that started the sending chain at 32 zero bytes was fixed on 8 September 2026 and ships in 1.0.44; and on the responder-first path the initiator's first message comes from the X3DH output alone, before any ratchet step, which is inherent to the construction. The full status is written up here.

OSHI does implement X-Wing hybrid post-quantum key agreement — ML-KEM-768 combined with X25519, via CryptoKit's XWingMLKEM768X25519. It is hybrid only, never post-quantum alone, so a break of ML-KEM cannot leave a session weaker than it is today, and it fails closed rather than downgrading quietly. It is @available(iOS 26 / macOS 26) while the app deploys to iOS 17.5, and the policy is .hybridWhenAvailable, negotiated per conversation, so it engages only when both ends can. That is a statement about what OSHI does; it is not a claim about Signal, which publishes its own protocol work and should be read there.

The honest distinction overall is maturity of review: Signal has years of published third-party audits, while OSHI has not yet been through a public external audit. OSHI is MIT-licensed and open source, so the code is available for inspection — but "auditable" is not the same as "audited," and we say so plainly. Read our Signal Protocol guide and end-to-end encryption guide for the details.

Which should you choose?

Choose Signal if you want the most widely trusted, independently audited encrypted messenger, you are fine providing a phone number, and you need first-class desktop apps and a network effect that reaches your contacts today.

Choose OSHI if you want messaging without a phone number, resilience when the internet is unavailable or censored, and on-device AI — and you are comfortable being an early adopter of a newer app. Many privacy-minded users run both: Signal for everyday reach, OSHI for high-resilience and no-number scenarios. Both are open source, so you can verify the claims yourself.

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