http://www.rfc-editor.org/rfc/rfc4648.txt
RFC 4648: The Base16, Base32, and Base64 Data Encodings, S. Josefsson2006-10-01T23:00:00-00:00This document describes the commonly used base 64, base 32, and base 16 encoding schemes. It also discusses the use of line-feeds in encoded data, use of padding in encoded data, use of non-alphabet characters in encoded data, use of different encoding alphabets, and canonical encodings. [STANDARDS-TRACK]