OpenPGP is a signature and encryption standard specified by RFC4880. This standard achieves information and file signing/encryption through the use of private keys. One of the commonly used OpenPGP tools is GNU Privacy Guard, often abbreviated as GnuPG or GPG. In Windows, you can also use Kleopatra.
CanoKey implements the OpenPGP Card specification version 3.4, holding up to three keys: a signature key (SIG), an encryption key (DEC), and an authentication key (AUT).
Firmware versions 1.6.1 and earlier only support RSA public keys with e = 65537. Firmware version 2.0.0 and later support RSA3072 / RSA4096 key generation.