TBSL Specification

TBSL is a project-specific, time-based, lexicographically sortable identifier used by Infocyph\UID\TBSL.

This document defines the canonical TBSL text format and the generation rules used by this package.

Canonical Format

A canonical TBSL identifier is exactly 20 uppercase hexadecimal characters:

^[0-9A-F]{20}$

The canonical string represents 10 bytes, or 80 bits, of data. Lowercase hexadecimal and non-hexadecimal characters are not canonical TBSL values.

Field Layout

Character positions are 1-based.

| Characters | Length | Field | Description | |:--|--:|:--|:--| | 1-15 | 15 hex chars | Time-machine payload | Uppercase hexadecimal encoding of the decimal payload SSSSSSSSSSUUUUUUMM, left-padded with zeroes to 15 characters. | | 16-20 | 5 hex chars | Entropy or sequence | Random suffix by default, or a sequence suffix when sequenced mode is enabled. |

The decimal payload is composed as follows:

| Decimal digits | Length | Field | Description | |:--|--:|:--|:--| | 1-10 | 10 digits | Unix seconds | Seconds since the Unix epoch. | | 11-16 | 6 digits | Microseconds | Microsecond fraction of the current second. | | 17-18 | 2 digits | Machine ID | Machine identifier from 00 to 99. |

Generation

Generation accepts:

• `machineId`: integer from `0` to `99`; default is `0`.
• `sequenced`: boolean; default is `false`.

The generator:

1. Reads the current Unix time with microsecond precision.
2. Builds the decimal time sequence as `seconds + microseconds`.
3. Appends the two-digit machine ID to form `SSSSSSSSSSUUUUUUMM`.
4. Converts that decimal payload to hexadecimal and left-pads it to 15 characters.
5. Appends a 5-character hexadecimal suffix: - random mode: first 5 hex characters from 3 random bytes; - sequenced mode: the next sequence value for the `(type = "tbsl", machineId, timestamp)` key, encoded as hex and padded to 5 characters.
6. Returns the 20-character uppercase hexadecimal string.

Sequence providers should keep returned sequence values within the 20-bit suffix range, 0x00000 through 0xFFFFF.

Parsing

To parse a canonical TBSL value:

1. Validate the string against `^[0-9A-F]{20}$`.
2. Decode characters `1-15` from hexadecimal to the decimal payload.
3. Read the first 10 decimal digits as Unix seconds.
4. Read the next 6 decimal digits as microseconds.
5. Read the final 2 decimal digits as the machine ID.

The suffix is intentionally opaque. It is not needed to recover the timestamp or machine ID.

Ordering

Canonical TBSL strings sort lexicographically by their time-machine payload first. This preserves chronological ordering for generated IDs as long as system clocks move forward.

For IDs generated within the same microsecond and machine ID:

• random mode provides uniqueness through entropy, but not generation order;
• sequenced mode provides deterministic suffix ordering while the sequence value remains within the 5-character hexadecimal suffix.

If the clock moves backward, the implementation either waits for the next usable time sequence or throws, depending on the configured clock-backward policy.

Encodings

The canonical representation is uppercase hexadecimal. The package can also convert canonical TBSL values to and from:

• raw 10-byte binary;
• base16;
• base32;
• base36;
• base58;
• base62.

Alternate-base encodings are transport encodings only. They do not replace the canonical 20-character uppercase hexadecimal TBSL string.

Limits

• Canonical size: 20 hex characters.
• Binary size: 10 bytes.
• Timestamp precision: microseconds.
• Machine ID range: `0` through `99`.
• Suffix size: 5 hex characters, or 20 bits.
• Maximum suffix cardinality per `(timestamp, machineId)` key: 1,048,576 values.