Encoding & Number Bases
Modhex Encoder
Encode text bytes as YubiKey Modhex. Follow each byte's two nibble substitutions and the growing output in a separate table.
This tool runs open-source code from CyberChef by GCHQ (Apache License 2.0). See open-source credits.
Modhex substitutes cbdefghijklnrtuv for hexadecimal digits. Each input byte produces two letters.
The result uses the chosen delimiter and line width. The table shows each nibble substitution.
- Check how a known byte value appears in Yubico OTP Modhex.
Sources: Yubico: Hex to Modhex substitution
Map Hello to Modhex letters
Input: Hello
Settings: Delimiter Space, Bytes per line 0
Result: fj hg hr hr hv
H is byte 0x48. Modhex writes hex digit 4 as f and 8 as j, so H becomes fj.
Choose byte delimiters and distinguish hex input
- Enter the source text.
- Choose Delimiter and Bytes per line.
- Run the encoder and compare the byte rows with the output.
- Input is text, not a hexadecimal byte string.
- Text through U+00FF uses single-byte values. A higher character switches the complete input to UTF-8.
- Encoding alone does not create a valid YubiKey one-time password.