Encrypted messaging
without phone numbers.
Built on Signal's own cryptography. No account to create, no phone number to hand over, no tracking. Your identity is a key pair generated on your device. Open source from day one.
What Seald gives you
End-to-end encrypted
Your messages are encrypted on your device before they leave. The server routes ciphertext it cannot read - not to us, not to anyone. Built on the Signal Protocol, the same cryptography trusted by billions.
No phone number required
Your identity is a cryptographic key pair generated on your device. No phone number, no email, no personal information ever touches a server. Share your Seald ID by QR code or any channel you trust.
No tracking. No analytics.
No telemetry, no usage data, no third-party scripts. This website doesn't even use cookies. The server routes opaque encrypted blobs - it never analyses, profiles, or monetises your conversations.
Open source from day one
The entire codebase is public - every commit, every line, from the first day of development. Anyone can verify our claims. Reproducible builds are planned so you can confirm the app matches the published source.
Your messages, your keys
Every message is encrypted on your device before it's sent. The server never sees the contents - it just delivers an opaque blob to the recipient, whose device is the only thing that can decrypt it.
encrypt()
decrypt()
Encrypted on your device
Your message is encrypted with the Signal Protocol before it leaves your device. The encryption keys are generated locally and never shared with the server.
Server routes ciphertext
The server receives an encrypted blob. It knows where to deliver it, but cannot read, modify, or analyse what's inside. It's a courier, not a reader.
Decrypted by the recipient
Only the recipient's device holds the keys to decrypt the message. The Triple Ratchet derives new keys for every message with post-quantum protection - compromising one doesn't compromise others, even with a future quantum computer.
What we don't know about you
Messaging apps can claim anything. Here's what our server actually sees versus what it cannot. We'd rather you trust the architecture than trust us.
What the server sees
- That an IP address connected
- Connection timing and duration
- Traffic volume between endpoints
- Recipient fingerprints*
What the server cannot see
- Who you messaged
- What you said
- Message content or attachments
- Your private keys
- Your contact list
- When you read messages
* With sealed sender enabled, recipient fingerprints are also hidden from the server. The server sees only that someone sent something.
Honest caveat: Metadata protection is not absolute. A network observer can see that you connected to our server and when. If you require IP-level anonymity, Seald will support routing through Tor. For the highest threat models, no single application replaces comprehensive operational security.
Built on audited libraries, not marketing claims
Signal Protocol
PQXDH for session establishment (X3DH + Kyber1024 post-quantum key exchange). Triple Ratchet (Double Ratchet + SPQR) for message encryption with ongoing post-quantum protection. Uses libsignal-protocol-rust directly - Signal's own Rust implementation. Quantum-resistant from day one.
Identity
Ed25519 key pairs generated on-device. No centralised identity namespace, no registrar to subpoena. Your ID looks like SEALD:7K4F-Q2LR-9NXP-V8HT. Safety numbers let you verify contacts out-of-band.
Server architecture
Two-process split. Bun/Elysia handles all network I/O - WebSocket connections, message routing, REST API. Rust handles storage and cryptographic verification. They communicate over a Unix domain socket with length-prefixed protobuf frames. No HTTP framework for IPC.
Storage
SQLite with WAL mode. The simplest tool that handles the job - fewer moving parts means fewer things to break and a smaller audit surface. No distributed database when one isn't needed.
Infrastructure
HAProxy for TLS termination. No Cloudflare, no CDN, no third-party TLS termination. Every third party in the network path is a metadata leak and a subpoena target. DDoS mitigation via Digital Ocean L3/L4 protection and HAProxy stick-table rate limiting.
Message padding
Fixed-size padding buckets (256B, 1KB, 4KB, 16KB, 64KB, 256KB, 1MB). Every message is padded before encryption so that message size doesn't leak information through traffic analysis. A "yes" and a paragraph look the same on the wire within each bucket.
Open source and security
Open source
The entire codebase has been public from the first commit. No "open core" model, no proprietary components. The full git history is available - you can trace every decision, every change, every line of code from the beginning.
Security audit
A professional security audit is planned for Phase 4, targeting the Rust core library (seald-core) and the storage service (seald-server) - approximately 5,000 lines of focused cryptographic code. Firms under evaluation include Cure53, Trail of Bits, and NCC Group. The full audit report will be published.
Audit scope
The audit target is small by design. seald-core is pure Rust with zero I/O dependencies - bytes in, bytes out. This is where all cryptographic operations live. The I/O layer (Elysia) never touches key material and is lower priority.
Reproducible builds
Planned for Phase 6. When available, you'll be able to build the app from source and verify that the binary matches what's distributed. Until then, the published source code is the primary verification mechanism.
Important: Seald has not yet undergone an independent security audit. Do not rely on Seald for high-threat communications until an audit report has been published. We believe in earning trust through transparency, not claiming it prematurely.
Download Seald
No account to create. Download, open, and you exist. Your identity is generated on your device in seconds.
iOS
Coming soon
In developmentNative Swift · iOS 15+
Android
Coming soon
In developmentNative Kotlin · Android 8+
Linux and Windows builds are planned. Run your own server - self-hosting documentation coming soon.