PEM

A base64 certificate and key file format widely used in PKI.

Privacy Enhanced Mail is a widely used container format that encodes certificates, keys, and certificate chains as base64 text wrapped in clear header and footer lines. Despite its mail-oriented name, it is now a general PKI file format common on Unix and Linux systems and in web server configurations. Its readable text encoding contrasts with the binary DER format, and the two are convertible. A practical caution is that private keys in PEM files must be tightly protected, since the format provides no encryption unless the key is separately passphrase-protected.