Loading, exporting, and encoding public and private keys
When you're working with asymmetric ciphers, one of the first problems you'll need to deal with is managing public and private keys, including loading and saving them to files or transmitting them to another person.
Both public and private keys contain long sequences of bytes. In the case of RSA, for example, private keys contain at least two main factors: a modulus and a secret exponent, each one long 2048, 3072, or 4096 bits (256, 384, or 512 bytes). Being binary data, they are not representable in a human-readable format, cannot be copied/pasted easily, and so on. To make handling keys more convenient, thus, we usually encode them.
Encoding keys as PEM
There are multiple formats for encoding private and public keys, but the de facto standard is DER-encoded ASN.1 stored in a PEM block, or simply "PEM format." Without getting into the details, which are not useful for our discussion, a PEM file contains...
