Base32
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Base32 is a base-32 transfer encoding using the twenty-six letters A-Z and six digits 2-7.
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[edit] Software
Base32 is a notation for encoding arbitrary byte data using a restricted set of symbols which can be conveniently used by humans and processed by old computer systems which only recognize restricted character sets. It comprises a symbol set made up of 32 different characters, as well as an algorithm for encoding arbitrary strings using 8-bit characters into the Base32 alphabet. This uses more than one 5-bit Base32 symbol for each 8-bit input character, and thus also specifies requirements on the allowed lengths of Base32 strings (which must be multiples of 40 bits). The Base64 system, in contrast, is closely related but uses a larger set of 64 symbols.
[edit] Advantages
Base32 has three main advantages over Base64:
- The resulting character set is all one case (usually represented as uppercase), which can often be beneficial when using a case-insensitive filesystem, spoken speech, or human memory.
- The alphabet was selected to avoid similar-looking pairs of different symbols, so the strings can be efficiently transcribed by hand. (For example, the symbol set omits the symbols for 1 and zero, since they could be confused with the lower-case 'L' and the letter 'O'.)
- The result can be included in a URL without encoding any characters.
[edit] RFC 4648 Base32 alphabet
The most widely used Base32 alphabet is defined in RFC 4648. It uses an alphabet of A–Z, followed by 2–7 (thus "2" actually has a numerical value of 26). 0 and 1 are skipped due to their similarity with the letters O and I.
| Value | Symbol | Value | Symbol | Value | Symbol | Value | Symbol |
|---|---|---|---|---|---|---|---|
| 0 | A | 9 | J | 18 | S | 27 | 3 |
| 1 | B | 10 | K | 19 | T | 28 | 4 |
| 2 | C | 11 | L | 20 | U | 29 | 5 |
| 3 | D | 12 | M | 21 | V | 30 | 6 |
| 4 | E | 13 | N | 22 | W | 31 | 7 |
| 5 | F | 14 | O | 23 | X | ||
| 6 | G | 15 | P | 24 | Y | ||
| 7 | H | 16 | Q | 25 | Z | ||
| 8 | I | 17 | R | 26 | 2 | pad | = |
[edit] Alternate versions
z-base-32 is a Base32 encoding designed to be easier for human use and more compact. It includes 8 and 9 but excludes v and 2. It also permutes the alphabet so that the easier characters are the ones that occur more frequently. It compactly encodes bitstrings whose length in bits is not a multiple of 8, and omits trailing padding characters. z-base-32 was used in Mnet open source project, and is currently used in Phil Zimmermann's ZRTP protocol, and in the Allmydata-Tahoe open source project.
An earlier form of base 32 notation was used by programmers working on the Electrologica X1 to represent machine addresses. The "digits" were represented as decimal numbers from 0 to 31. For example, 12-16 would represent the machine address 400.
Another alternative design for Base32 is created by Douglas Crockford, who proposes using additional characters for a checksum.[1]
| Value | Encode Digit | Decode Digit | Value | Encode Digit | Decode Digit |
|---|---|---|---|---|---|
| 0 | 0 | 0 | 16 | G | g G |
| 1 | 1 | 1 | 17 | H | h H |
| 2 | 2 | 2 | 18 | J | j J |
| 3 | 3 | 3 | 19 | K | k K |
| 4 | 4 | 4 | 20 | M | m M |
| 5 | 5 | 5 | 21 | N | n N |
| 6 | 6 | 6 | 22 | P | p P |
| 7 | 7 | 7 | 23 | Q | q Q |
| 8 | 8 | 8 | 24 | R | r R |
| 9 | 9 | 9 | 25 | S | s S |
| 10 | A | a A | 26 | T | t T |
| 11 | B | b B | 27 | V | v V |
| 12 | C | c C | 28 | W | w W |
| 13 | D | d D | 29 | X | x X |
| 14 | E | e E | 30 | Y | y Y |
| 15 | F | f F | 31 | Z | z Z |
[edit] base32hex
Triacontakaidecimal is another alternative design for Base 32, that extends Hexadecimal in a more natural way. RFC 4648 uses base32hex as name for this encoding deployed in RFC 2938. Note the difference between 0, O and 1, I. They are similar, but still distinguishable in ASCII. In binary it would end up represented in 8-bits, although it could be contained in 5, as 8-bits actually represents a base 256 numbering system.
| Triacontakia | Binary | Decimal |
|---|---|---|
| 0 | 00000 | 0 |
| 1 | 00001 | 1 |
| 2 | 00010 | 2 |
| 3 | 00011 | 3 |
| 4 | 00100 | 4 |
| 5 | 00101 | 5 |
| 6 | 00110 | 6 |
| 7 | 00111 | 7 |
| 8 | 01000 | 8 |
| 9 | 01001 | 9 |
| A | 01010 | 10 |
| B | 01011 | 11 |
| C | 01100 | 12 |
| D | 01101 | 13 |
| E | 01110 | 14 |
| F | 01111 | 15 |
| G | 10000 | 16 |
| H | 10001 | 17 |
| I | 10010 | 18 |
| J | 10011 | 19 |
| K | 10100 | 20 |
| L | 10101 | 21 |
| M | 10110 | 22 |
| N | 10111 | 23 |
| O | 11000 | 24 |
| P | 11001 | 25 |
| Q | 11010 | 26 |
| R | 11011 | 27 |
| S | 11100 | 28 |
| T | 11101 | 29 |
| U | 11110 | 30 |
| V | 11111 | 31 |
[edit] Video games
Before NVRAM became universal, several video games for Nintendo platforms use base 32 numbers for passwords. These systems omit vowels to prevent the game from accidentally giving a profane password. Thus, the characters are generally some minor variation of the following set: 0-9, B, C, D, F, G, H, J, K, L, M, N, P, Q, R, S, T, V, W, X, Y, Z, and some punctuation mark. Games known to use such a system include Mario Is Missing!, Mario's Time Machine, Tetris Blast, and The Lord of the Rings (Super NES).
