Base64 Encoding

The standard base64 encoding algorithm (as specified in [RFC4648]) is used to transmit binary data. Base64 processes data as 24-bit groups, mapping it to four encoded characters of 6 bits each. It is sometimes referred to as 3-to-4 encoding. Each 6-bit group in the 24-bit group is used as an index into a mapping table (see section to obtain a character for the encoded data. By convention, line lengths in the encoded data are limited to 76 characters, but this is not strictly enforced in this protocol.

Note The characters used in base64 encoding do not include any of the special characters of the Simple Mail Transfer Protocol (SMTP) (as specified in [RFC2821]), or the hyphen used with Multipurpose Internet Mail Exchange (MIME) boundary strings, as specified in [RFC2045].