If you are into Cybersecurity, Base-64 should be a well-known format, and often used to convert binary data into a text format. In Bitcoin, we use Base-58 for the Bitcoin address. But, what is Base-45?

Well, your vaccine status document probably contains a QR code, and which uses Base-45 format for the data coding [article]. With Base-45 format, we have 45 characters defined. The encoding table is [here]:

`Value Encoding Value Encoding Value Encoding Value Encoding`

00 0 12 C 24 O 36 Space

01 1 13 D 25 P 37 $

02 2 14 E 26 Q 38 %

03 3 15 F 27 R 39 *

04 4 16 G 28 S 40 +

05 5 17 H 29 T 41 -

06 6 18 I 30 U 42 .

07 7 19 J 31 V 43 /

08 8 20 K 32 W 44 :

09 9 21 L 33 X

10 A 22 M 34 Y

11 B 23 N 35 Z

With this we take the data stream with two bytes [A, B] at a time, and and convert into [ C, D, E] and where:

(A*256) + B = C + (D*45) + (E*45*45).