Tool for coding with Base45 encoding, using 45 ASCII characters, which has become known since its use in the European green pass/certificate.
Base45 Encoding - dCode
Tag(s) : Character Encoding
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Base45 Encoding
Base45 Decoder
Base45 Encoder
Answers to Questions (FAQ)
What is Base-45? (Definition)
How to encode using Base-45?
The Base45 encoding consists in writing the data in base 45 and using the following list of symbols 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./: Which corresponds to the 45 characters that can be used in a QR-code in alphanumeric mode so the correspondance table:
| Index | Character Base45 |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 4 |
| 5 | 5 |
| 6 | 6 |
| 7 | 7 |
| 8 | 8 |
| 9 | 9 |
| 10 | A |
| 11 | B |
| 12 | C |
| 13 | D |
| 14 | E |
| 15 | F |
| 16 | G |
| 17 | H |
| 18 | I |
| 19 | J |
| 20 | K |
| 21 | L |
| 22 | M |
| 23 | N |
| 24 | O |
| 25 | P |
| 26 | Q |
| 27 | R |
| 28 | S |
| 29 | T |
| 30 | U |
| 31 | V |
| 32 | W |
| 33 | X |
| 34 | Y |
| 35 | Z |
| 36 | |
| 37 | $ |
| 38 | % |
| 39 | * |
| 40 | + |
| 41 | - |
| 42 | . |
| 43 | / |
| 44 | : |
Encoding begins by cutting the data to be encoded from left to right in groups of 2 bytes. If the data has an odd number of bytes, the last group is 1 byte in size.
Example: Encode the 3 characters B45, of ASCII code [66,52,53], which are then split [66,52],[53]
Each pair of 2 bytes $ [a, b] $ is interpreted as a number in base $ 256 $ such that $ n = (a \times 256) + b $ (in base 10) which can then be converted into base 45 via a triple $ [c,d,e] $ such that $ n = c + (d \times 45) + (e \times 45^2) $. The characters in the correspondence table for the values '[c, d, e]' are noted (in that order) as encoded text.
Any last single byte $ a $ at the end of the data is also interpreted as a number in base 256 and converted to a pair $ [b,c] $ such that $ a = b + (45 \times c) $. The characters in the correspondence table for the values [b,c] are noted (in that order) as encoded text.
Example: The couple [66,52] corresponds to the number 66 * 256 + 52 = 16948 and 16948 = 28 + 16 * 45 + 8 * 45 ^ 2, so the triplet [28,16,8] that is equivalent to the characters S,G,8 in base45
The remaining byte [53] is written in base 45 as follows: 53 = 1 * 45 + 8, either the pair [1,8] or the characters 1,8 in base45. The full encoding of B45 in base45 is SG881
How to decode Base-45?
For any string written in Base45, start by converting the characters into numeric values (according to the correspondence table).
Example: Decode SG881, or the values [28,16,8,8,1]
Divide the values into groups of 3, from left to right. If the last group of 3 is not complete, add zeros 0 at the end.
Example: [28,16,8,8,1] splits as [28,16,8],[8,1,0]
Interpret each group [c,d,e] as a number in base 45 as follows: $ n = c + (d \times 45) + (e \times 45^2) $ and note the values $ n $ obtained
Example: [28,16,8],[8,1,0] is converted to [16948],[53]
Convert each number to base 256 (so in bytes)
Example: 16948 = 66 * 256 + 52 or [66,52] and 53 remains [53] in base 256
The decoded message is the set of bytes. It can be interpreted in ASCII code (or Unicode)
Example: [66,52,53] for the 3 ASCII characters B,4,5 (plaintext)
How to recognize a Base-45 ciphertext? (Identification)
Base-45 uses the 36 uppercase alphanumeric characters 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ completed with the characters (space)', $ (dollar), % (percent), * (asterisk), + (plus), - (minus/dash), . (period), / (slash) and : (colon).
Base-45 is optimized to transmit data with the alphanumeric mode of QR-codes.
It has been used in COVID-19 vaccines certificates and European Union green passes.
Source code
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Cite as source (bibliography):
Base45 Encoding on dCode.fr [online website], retrieved on 2024-12-21,
