Normalized sender-data string

A normalized sender-data string is used to unambiguously specify binary sender data for a transaction.

The sender-data field in a transaction may contain from 0 to 32 bytes, and those bytes often represent a UTF-8 encoded character string. Therefore, many input strings could be ambiguous without further information. For example, "aa" could represent the hexadecimal value aa (decimal 170), or it could simply be a text string, which would be encoded as hexadecimal 6161.

To reduce the probability for confusion, the Nyzo tools will continue to interpret most sender-data input as text strings, encoding them in UTF-8 for storage in the sender-data field. The one exception will be the normalized sender-data string, which will be used to directly specify the byte values of the sender-data field.

A normalized sender-data string is defined as follows.

• case-insensitive (aa and AA are equivalent)
• exactly 67 characters long
• the first character is "X" or "x"
• the second character is "("
• the final character is ")"
• the remaining characters are the data section
  • exactly 64 characters long
  • left side is a hex string (0-9, a-f, or A-F)
  • right side is underscores
  • left side is 0 to 64 characters long, in increments of 2 (0, 2, 4, 6, 8, ..., 60, 62, 64)
  • right side is 0 to 64 characters long, in increments of 2

An empty data field would be represented by a normalized sender-data string with a data section of underscores only.

X(________________________________________________________________)

The character string "Nyzo" would be represented by a normalized sender-data string whose data section begins with hexadecimal representation of the UTF-8 encoding of "Nyzo" and pads the remaining characters with underscores.

X(4e797a6f________________________________________________________)

The previous two examples can be input properly in all of the Nyzo tools as character strings. Normalized sender-data strings were designed specifically for data that cannot be input properly as character strings. For instance, the Git hash of the first commit containing NTTP-2 is 297632ff2f9c810c2cca1f3a2b3ac320aea04ac9. The correct sender-data field to indicate support for this proposal at that commit would contain the UTF-8 encoding of "NTTP 2: " followed by the bytes of the hash, 297632ff2f9c810c2cca1f3a2b3ac320aea04ac9.

X(4e5454502d323a20297632ff2f9c810c2cca1f3a2b3ac320aea04ac9________)

This format was introduced in version 559 for generation of NTTP sender-data fields, and full support across all Nyzo tools will be an ongoing effort.