Ed25519.
The signing half of your identity. Ed25519 is a fast, compact, widely audited signature scheme on the Curve25519 family — the same algorithm trusted by SSH, TLS, and most modern secure systems.
Ed25519 is the Edwards-curve Digital Signature Algorithm (EdDSA) instantiated on the edwards25519 curve, standardized in RFC 8032. In CarrierPony it produces the signature attached to every outgoing envelope.
What it is
Your Ed25519 private key signs each message and file before it leaves your phone. The recipient's app verifies that signature against your public key before showing the content, proving both who sent it and that nothing changed in transit.
Why it matters
Ed25519 keys are 32 bytes, signatures are 64 bytes, signing is effectively instant, and the design avoids entire classes of implementation mistakes that plagued older signature schemes. That combination is why the modern cryptographic world converged on it.
Related terms
Common questions.
Is Ed25519 the same as Curve25519?
They're siblings on the same curve family. Ed25519 signs; X25519 on Curve25519 handles encryption key agreement. CarrierPony uses both — one key for each job.
Why not RSA?
RSA still works, but its keys are ten times larger, operations are slower, and safe use requires more care. Ed25519 gives equivalent-or-better security with far less to get wrong.
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