Base64 encoder / decoder

Base64 is an encoding scheme used to encode binary data in plain text.
An example to such binary-to-text usage is PEM certificates: A certificate in PEM format is an ASCII representation in base64 of the binary DER format.
Base64 is also often used to obscure text. In that sense, we encode an ASCII text to a different representation of ASCII.
But such encoding is by no means an encryption, since it doesn't use an encryption key, and can be decoded by anyone