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Keycode Description Keycode is a transcription friendly 256-bit key format. It takes a key like this: d642d9650d7bd3d895cd04888dc70da684c74732a9daadc785d205 and converts it into something like TR1 DJR 8D6 FF9 WH5 EDJ G9V 4H0 20C 0J4 8UH QDF LT2 CEH RJ4 M7D AUH V5E 684 136 109 for the purpose of human transcription and possibly spoken key-exchange. Design The representation is brief, requiring fewer characters than the hexadecimal encoding, nevertheless there are a number of important advantages: • A tabular layout makes for easy visual confirmation that a key is complete: 7 rows of three alphanumeric triples. • A limited character set avoids the characters I, O, S, Z since they may be mistaken for digits. • The digit grouping increases readability and encourages consistent verbal communication when needed.

• Every row is protected by a checksum digit that can detect exactly one changed, or one transposed digit. The last row may be used as the basis of partial key verification, to assist with this: • The row consists only of digits (which can be clearly spoken in all languages and may be easily typed on a keypad) • The groups never contain adjacent digit pairs (like 77), this avoids the use of idiomatic verbal constructs (such as 'double 7'). • No group in the row begins with a zero yielding regular three digit numbers.

Ergonomics and error detection combine to form a convenient format for written and spoken 256-bit key exchange. Usage A Java library for parsing and formatting keycode is available from the Maven central repository: Group ID: com.tomgibara.keycode Artifact ID: keycode Version: 1.0.0 The Maven dependency being: com.tomgibara.keycode keycode 1.0.0 The library is very simple, consisting of just two abstractions: the Keycode.Format class which encapsulates formatting rules, and the Keycode class which combines key data with a format. To use the library you will need to be working with 256-bit keys. KeyGenerator keygen = KeyGenerator.getInstance('AES'); keygen.init(256); byte[] key = keygen.generateKey().getEncoded(); You can then produce a keycode in a standard format, simply and fluently: String standard = Keycode.Format.standard().keycode(key).toString(); This will produce output something like: G8J HTV TFU 5U5 YNE WE2 535 VF4 3FW R34 1B6 87A 5CM BJ6 RR2 U78 9W2 AC9 287 304 101 For some applications, it may be useful to produce the keycode without any whitespace. String plain = Keycode.Format.plain().keycode(key).toString(); // G8JHTVTFU5U5YNEWE2535VF43FWR341B687A5CMBJ6RR2U789W2AC A Keycode.Format.platform() format is also available which uses platform dependent line separators. Formats using custom whitespace are also possible using Keycode.Format.custom(). Parsing a keycode is also simple and fluent: byte[] key = Keycode.Format.standard().parse(standard).getKey(); Failure to parse a keycode (for any reason, including the presence of invalid characters, invalid structure, detected errors, etc.) will be reported with an IllegalArgumentException from the parse() method.