3.1.5.1 Data Encoding and Decoding
Base64 Encoding and Decoding: The standard base64 encoding algorithm (as specified in [RFC4648]).
The characters used in base64 encoding do not include any of the special characters of the Simple Mail Transfer Protocol (SMTP) [RFC2821], or the hyphen used with Multipurpose Internet Mail Exchange (MIME) boundary strings, as specified in [RFC2045].
Base64 Mapping Table: The base-64 mapping table is defined as follows.
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0 A 17 R 34 i 51 z 1 B 18 S 35 j 52 0 2 C 19 T 36 k 53 1 3 D 20 U 37 l 54 2 4 E 21 V 38 m 55 3 5 F 22 W 39 n 56 4 6 G 23 X 40 o 57 5 7 H 24 Y 41 p 58 6 8 I 25 Z 42 q 59 7 9 J 26 a 43 r 60 8 10 K 27 b 44 s 61 9 11 L 28 c 45 t 62 + 12 M 29 d 46 u 63 / 13 N 30 e 47 v 14 O 31 f 48 w 15 P 32 g 49 x 16 Q 33 h 50 y