Asymmetric cryptography (also called public-key cryptography) is a cryptographic system that uses multiple keys—usually a "public" and "private" key.
Read more about public-key cryptography on Wikipedia.
A popular asymmetric cryptography algorithm is RSA. RSA has two key types: public and private.
RSA can create signatures from any data using a private key.
let privateKey: String = ... let signature = try RSA.SHA512.sign("vapor", key: .private(pem: privateKey))
Only private keys can create signatures.
These signatures can be verified against the same data later using either the public or private key.
let publicKey: String = ... try RSA.SHA512.verify(signature, signs: "vapor", key: .public(pem: publicKey)) // true
If RSA verifies that a signature matches input data for a public key, you can be sure that whoever generated that signature had access to that key's private key.
RSA supports any of the Crypto module's
let privateKey: String = ... let signature512 = try RSA.SHA512.sign("vapor", key: .private(pem: privateKey)) let signature256 = try RSA.SHA256.sign("vapor", key: .private(pem: privateKey))