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Bastion is end-to-end encrypted by default. There’s no toggle to forget: every message, file and call is sealed on the sender’s device and opened only on the recipients’. The server — even one you run yourself — only ever handles ciphertext.

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The building blocks

Bastion’s encryption is built on vetted, widely-audited cryptography (X25519 key exchange, XChaCha20-Poly1305 for content, Argon2id for your passphrase). You don’t have to think about any of that day to day — it’s the foundation the features below stand on.

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Verify who you’re talking to

End-to-end encryption protects you from everyone except an attacker who can quietly swap keys in transit. To close that gap, every conversation has a safety number both sides can compare:
1

Open the chat info

From a chat’s header, open its info page and find a member’s safety number.
2

Compare it

Compare the number in person, over a call, or through another trusted channel.
3

You're verified

If they match, no one is in the middle. If they don’t, stop and investigate.

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Your key, your backup

Your identity key lives on your device. From the Security screen you can:
  • Back it up with a passphrase you choose, and download or copy the backup.
  • Restore it on a new phone, laptop or browser — same account, same history, across every device you use.
The backup is protected by your passphrase and the server never has it. If you lose both the passphrase and every signed-in device, that key can’t be recovered — by design. Keep the backup somewhere safe.

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What the server can and can’t see

  • Can’t see: your message text, file contents, or call media — all end-to-end encrypted.
  • Can see: the minimum needed to route traffic — who is in an organization, and delivery metadata (the “envelope”, not the content). Message sizes are padded so even encrypted length reveals little. Identity and licensing are brokered centrally; see Accounts & privacy for the full picture of what metadata is visible and how metadata-minimal mode narrows it further.

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History that follows you

Bastion deliberately keeps your history available to your new devices and to teammates you add — the way a team chat should work. That’s a conscious trade-off in favor of a usable team tool, and it’s why the key backup above matters.