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Appendix C. Base64 Encoding

Base64 encoding was originally described in 1993 in the Internet Engineering Task Force's RPC 1421, a specification for e-mail encryption and authentication. Since that time, Base64 has been employed in a number of protocols and technologies, including MIME and XML. Base64 is a simple encoding algorithm, used to convert binary data into blocks of ASCII characters. It is useful in technologies that are text-based, such as SMTP (e-mail) and XML.

The “64” in Base64's name comes from its use of 64 ASCII characters to represent all possible byte values.^[1] Base64 uses a special conversion table to assign one of 64 ASCII characters to every six bits of a byte stream. In other words, a binary stream is sliced up into six-bit ...