Clockwork Base32 is a simple variant of Base32 inspired by Crockford's Base32.
See also a blog post (in Japanese).
- Specification Version
- Last updated
- Features
- Difference Between Clockwork Base32 and Other Specifications
- Symbols
- Algorithm
- Implementations
- Examples
- License
- Author
- Acknowledgements
- Uses
- Links
- Specification Revision History
- Document Revision History
2020.2 (Updated: 2020-07-27)
2021-06-06
- Human readable
- Octet-aligned binary support
- No padding character at end of encoded text
- Easy to implement (recommends using bitstring libraries)
| RFC 4648 | Crockford's Base32 | Clockwork Base32 | |
|---|---|---|---|
| Human readable | Not needed | Needed | Needed |
| Input data | Octet sequence | Integer | Octet sequence (byte array) |
| Encoded representation | ASCII character sequence | Symbol sequence | ASCII character sequence |
| Symbols | 32 alphanum + 1 sign characters | 32 alphanum + 5 sign characters (optional) | 32 alphanum characters |
| Padding of encoded data | Used | None | None |
| Ignored characters in decoding | Non-alphabet characters (optional) | Hyphen | None |
| Checksum | None | 1 character (Optional) | None |
- Clockwork's Base32 symbol set is equal to Crockford's Base32's excluding 5 symbols (
*~$=U) for checksum. - Symbol is 1 ASCII character.
- Case-insensitive.
| Value | Decode | Encode |
|---|---|---|
| 0 | 0 O o |
0 |
| 1 | 1 I i L l |
1 |
| 2 | 2 |
2 |
| 3 | 3 |
3 |
| 4 | 4 |
4 |
| 5 | 5 |
5 |
| 6 | 6 |
6 |
| 7 | 7 |
7 |
| 8 | 8 |
8 |
| 9 | 9 |
9 |
| 10 | A a |
A a |
| 11 | B b |
B b |
| 12 | C c |
C c |
| 13 | D d |
D d |
| 14 | E e |
E e |
| 15 | F f |
F f |
| 16 | G g |
G g |
| 17 | H h |
H h |
| 18 | J j |
J j |
| 19 | K k |
K k |
| 20 | M m |
M m |
| 21 | N n |
N n |
| 22 | P p |
P p |
| 23 | Q q |
Q q |
| 24 | R r |
R r |
| 25 | S s |
S s |
| 26 | T t |
T t |
| 27 | V v |
V v |
| 28 | W w |
W w |
| 29 | X x |
X x |
| 30 | Y y |
Y y |
| 31 | Z z |
Z z |
Excluded Characters: U
- Proceeding from left to right, map each 5 bits representation of input data as block length to a symbol character (upper-case recommended). If length of the most right block is under 5 bits, fill with zero bits.
- Combine the symbol characters into a sequence.
- Return the sequence.
Bit length of decoded data must be greater than or equal to bit length of the plain data.
- Proceeding from left to right, map each character of input data to 5 bits representation.
- Combine the 5 bits blocks into an octet sequence. If the sum of the block length is indivisible by 8, truncate most right bits which length is equal to a remainder of division by 8.
- Return the octet sequence.
Some error cases:
- Including invalid characters: e.g.
uU*=
Some corner cases:
- If an input data is 1 character (e.g.
0), decoder may return an empty octet sequence or report as error. - Padding length may be greater than or equal to 5-7 bits. For example, if input data is 3 characters, it represent 15 bits which is 1 character and padding 7 bits. Both of input data
CR0andCRcan be decoded asf.
- Encoded data does not contain error detection information. Use this algorithm together with any other error detection algorithm to detect errors.
| Input | Encoded |
|---|---|
| (empty) | (empty) |
f |
CR or CR0 |
foobar |
CSQPYRK1E8 |
Hello, world! |
91JPRV3F5GG7EVVJDHJ22 |
The quick brown fox jumps over the lazy dog. |
AHM6A83HENMP6TS0C9S6YXVE41K6YY10D9TPTW3K41QQCSBJ41T6GS90DHGQMY90CHQPEBG |
These reference implementations basically are for help with understanding and implementing. You should not expect improving performance, good API and continuous maintenance.
- C: szktty/c-clockwork-base32
- Erlang: shiguredo/erlang-base32
- Go: szktty/go-clockwork-base32
- Swift: szktty/swift-clockwork-base32
- C++: wx257osn2/clockwork_base32_cxx
- C++: objectx/cpp-clockwork-base32
- JavaScript: mganeko/js_clockwork_base32
- AssemblyScript: mganeko/as_clockwork_base32
- Rust: woxtu/rust-clockwork-base32
- Rust: hnakamur/rs-clockwork-base32
- Go: shogo82148/go-clockwork-base32
- TypeScript: niyari/base32-ts
This document is distributed under CC BY-ND 4.0.
SUZUKI Tetsuya
Shiguredo Inc.
- WebRTC SFU Sora by Shiguredo Inc.
- used for encoding and decoding UUID to be readable and shorten (32 characters -> 26 characters).
- Crockford's Base32
- Formal Verification of Encoding and Decoding
- A sample script (Isabelle/HOL)
- Thanks @pirapira!
2020.2 (2020-07-27)
- [CHANGE] Added decoding specification for some corner cases. Thanks @pirapira!
- [CHANGE] Changed decoding 1 character from invalid to valid.
2020.1 (2020-07-20)
- First release.
2021-06-06
- [CHANGE] Added a third-party implementation.
- niyari/base32-ts
2021-02-11
- [CHANGE] Added third-party implementations.
- shogo82148/go-clockwork-base32
- mganeko/as_clockwork_base32
- hnakamur/rs-clockwork-base32
2020-08-11
- [CHANGE] Added "Uses" section.
2020-08-01
- [CHANGE] Added a reference implementation.
- szktty/swift-clockwork-base32
- [CHANGE] Added some links.
2020-07-30
- [CHANGE] Added a reference implementation.
- szktty/c-clockwork-base32
2020-07-27
- Released 2020.2.
- [CHANGE] Added a table of contents.
2020-07-26
- [CHANGE] Added a third-party implementation.
- woxtu/rust-clockwork-base32
2020-07-25
- [CHANGE] Added third-party implementations.
- wx257osn2/clockwork_base32_cxx
- objectx/cpp-clockwork-base32
- mganeko/js_clockwork_base32
2020-07-22
- [CHANGE] Added RFC 4648 to the comparison table of specification.
- [FIX] Input
Hello, worldis incorrect.Hello, world!is correct. Thanks @mganeko!
2020-07-20
- First release.
Hi, thank you for nice spec.
I guess the input of an example 'Hello world' is 'Hello world!'.
'Hello, world' --> 91JPRV3F5GG7EVVJDHJ0
'Hello, world!' --> 91JPRV3F5GG7EVVJDHJ22