Public vs private key.
The asymmetric pair that makes all of this work. One half is meant to be shared; the other must never be. Mixing up which is which is the classic beginner hazard — CarrierPony is built so you can't.
A public key can be handed to anyone: it lets them encrypt messages to you and verify your signatures. The matching private key stays on your device: it decrypts what was encrypted to you and creates your signatures.
What it is
When you pair with someone, the two of you exchange public keys — that's all pairing is. From then on, your app encrypts to their public key and signs with your private key; theirs does the mirror image.
Why it matters
Asymmetric keys are what let two people who have never shared a secret start communicating securely. There is no password to exchange and nothing sensitive in the pairing itself — intercepting a public key gains an attacker nothing except the ability to send you encrypted mail.
Related terms
Common questions.
Can someone with my public key read my messages?
No. The public key only encrypts and verifies. Reading requires the private key, which never leaves your device.
What happens if my private key leaks?
Whoever holds it can read messages encrypted to you and sign as you. That's why it lives only on your device and in a passphrase-encrypted backup — and why the app can add a Face ID lock on top.
Get CarrierPony
Free private messaging and file transfer for iPhone. No accounts, no tracking, no phone numbers.