Secure Business Messaging · An Attomus Product
Communication that stays contained.
SemaFore is secure messaging for teams that need private conversations, file exchange, and controlled communications to remain between the intended parties — without relying on consumer-grade handling or hoping the platform provider does the right thing.
The server routes your messages. It cannot read them.
That is not a policy. It is how the architecture works.
How it works
Tighter handling without asking you to trust us.
Messages leave your device already sealed
SemaFore encrypts every message on-device using a session key the server never sees. The underlying protocol is Signal (X3DH key agreement + Double Ratchet forward secrecy) — the same standard used by organisations with an active interest in not being intercepted.
The server routes. It does not read.
The SemaFore server receives ciphertext and forwards it. There is no moment where message content exists in plaintext on any Attomus-operated system. Decryption requires keys that live only on your devices. This is not a configuration option. It is the architecture.
Administration without surveillance
Platform administrators have a full audit trail of activity — who sent to whom, when, file transfers, group membership changes — and no access to content. Governance and discretion are not in tension. They are the same thing.
The Platform
An admin portal that shows activity, not content.
The SemaFore admin portal gives operations and compliance teams visibility into platform activity, user management, and communication volumes — without a single word of message content. Organisations under meaningful scrutiny can govern the platform without the platform becoming a liability.
Messaging teams can use without a briefing.
The mobile clients — iOS and Android — work like a modern messaging application. End-to-end encryption runs without user intervention. Communication stays moving across offices, travel, and distributed teams without relying on consumer tools or workarounds.
Made by Attomus
Built by Attomus for organisations that need dependable handling.
Attomus works with government, defence, and regulated enterprise on cybersecurity and programme delivery where the standards are high and follow-through matters. SemaFore comes from the same focus: tighter handling, dependable execution, and tools that solve a specific operational need.
sema — sign, signal. fore — prominent, forward-facing.
JOSCAR Registered
Pre-qualified for defence, aerospace, and security procurement.
Armed Forces Covenant
Signatory. Attomus operates with the conduct that sensitive environments require.
Mayfair, London
Registered in England & Wales. No.
For Organisations
Built for work that carries real risk.
Data Sovereignty
All server infrastructure runs on Attomus-owned hardware in the United Kingdom, behind Attomus's own network boundary.
No hyperscale cloud provider — no AWS, Azure, or GCP — processes or stores your organisation's data. Databases, message queue, and key store are on Attomus infrastructure. Data does not leave UK jurisdiction in normal platform operation.
ICO Registered
ZA718457
UK GDPR Compliant
Contained messaging
Private and group threads, encrypted end-to-end. Messages stay between the intended parties.
Secure file exchange
Files are encrypted client-side before upload. The server stores ciphertext and never sees the content.
Organisation administration
Manage users, groups, and platform governance without accessing message content.
Full audit trail
Every platform event logged with actor, timestamp, and type. No content. No surprises.
Push delivery without exposure
Notification payloads contain no message content. Devices fetch and decrypt on wake.
Forward secrecy built in
Key rotation and one-time pre-key replenishment run automatically. Sessions stay forward-secret.
Pricing
Free for small teams. Professional when you need scale. Enterprise when contracts matter.
Every tier includes the same encryption model and apps. The differences are seats, retention, analytics, and support.
Free
£0
Up to 5 users · No time limit
- Private and group messaging
- Broadcast to all members
- iOS and Android apps
- Admin portal
- Audit log
- Up to 5 approved members
Professional
£9 / user / month
Billed annually · no seat ceiling
£11 / user / month billed monthly
- Everything in Free
- Unlimited approved members
- Audit log with 90-day retention and CSV export
- Usage analytics dashboard
- Message delivery indicators
- Email support
- 30-day trial · card required · up to 25 seats during trial · cancel any time
Enterprise
Custom
Complex deployments · Custom terms
- Everything in Professional
- Unlimited audit log retention
- 4-hour SLA
- Dedicated customer success manager
- DPA negotiation and custom contract
Free tier — early access notice: The free tier is available as part of our early-access launch. If availability changes, organisations on the free tier will receive at least 90 days' written notice and can move to a paid plan at the standard rate.
Government and defence: Device attestation and on-premise deployment options are available for government, defence, and classified-adjacent organisations. These options are negotiated separately and are not on the standard rate card. Contact us directly to discuss requirements and timelines.
Discuss a Requirement
Secure communications
handled properly.
Tell us how your team works and we’ll tell you whether SemaFore fits. Most first conversations take no more than twenty minutes.