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The Base64 encoding is a simple form of cipher used to safely encode files and data objects containing binary (non-printable, non-ASCII) bytes; it encodes a quantum of three 8-bit bytes as four 7-bit printable ASCII characters. It was inspired by Unix uuencode(1), which used a set of printable ASCII characters that were not safe from translation issues when passing mail between Unix systems based on ASCII and IBM systems using EBCDIC. Base64 uses 64 characters (and one padding character) that are "invariant" between ASCII and EBCDIC code pages, thus an ASCII "A" will always translate into EBCDIC "A" and back again without issue; this is true for all of the Base64 characters: upper and lower case letters (A-Za-z), numeric digits (0-9), plus-sign (+), slash (/), and equals-sign (=).