USBN v1.0

Overview

This document specifies the Universal Standard Book Number (USBN) v1.0, a deterministic, registry-free, 13-character alphanumeric identifier for books derived from bibliographic metadata. USBNs require no central registry and can be independently computed by any party with access to a book's title page.

Identifier format

A USBN is a 13-character string matching the regular expression:

U[0-9A-HJKMNP-TV-Z]{12}

That is: the literal letter U followed by exactly 12 characters from the Crockford Base32 alphabet. A WSBN has the same data format but begins with W and is computed without the year.

USBNs and WSBNs are case-insensitive. A conformant parser MUST uppercase its input before validation or lookup. The canonical display form is uppercase, but uazja136wfyxf and UAZJA136WFYXF MUST resolve to the same identifier.

Input specification

A USBN is computed from three fields:

Field	Type	Source
TITLE	string	Title as printed on the title page
AUTHOR	string	Author as printed on the title page
YEAR	integer	Four-digit publication year

For a WSBN the YEAR field is omitted.

Canonical input string

The canonical input string for a USBN is formed as:

S = NORMALIZE(TITLE || " " || AUTHOR || " " || STR(YEAR))

For a WSBN:

S = NORMALIZE(TITLE || " " || AUTHOR)

Normalisation pipeline

An implementation MUST apply the following steps in order:

1. Concatenation with a single ASCII space between fields.
2. NFKD decomposition (Unicode normalisation form KD).
3. Combining-character stripping: remove all characters in Unicode general category M (Mark).
4. Uppercase using locale-independent Unicode case mapping.
5. Whitespace collapse: replace each run of Unicode whitespace with a single ASCII space.
6. Trim leading and trailing whitespace.

Alphabet

The alphabet is Crockford Base32 — 32 characters, single case, excluding the four letters I, L, O, and U which are the most visually ambiguous in handwriting and print:

0 1 2 3 4 5 6 7 8 9 A B C D E F G H J K M N P Q R S T V W X Y Z

Hash function

BLAKE2s (RFC 7693) is used with an 8-byte (64-bit) digest, no key, no salt, no personalisation. The hash input is the UTF-8 encoding of the canonical input string.

Encoding procedure

Given the 8-byte BLAKE2s digest H:

1. Compute n64 = BE(H) (64-bit unsigned integer).
2. Compute n = n64 >> 4 (the top 60 bits).
3. Encode n in Crockford Base32, most-significant digit first.
4. Left-pad with 0 to exactly 12 characters.
5. Prepend U for a USBN or W for a WSBN.

Twelve Crockford Base32 characters encode exactly 32¹² = 2⁶⁰ values. Taking 60 bits of BLAKE2s output gives a lossless, padding-free encoding.

Collision analysis

A 60-bit hash space contains 2⁶⁰ ≈ 1.15 × 10¹⁸ possible values. 50% birthday collision probability occurs at approximately 1.26 billion entries.

Corpus	Size	P(≥1 collision)
Typical library	1 M	0.00004 %
Large union catalog	10 M	0.004 %
Pre-ISBN corpus	60 M	0.156 %
Estimated global corpus	150 M	0.97 %

Canonical test vectors

Any conformant implementation MUST produce these identifiers for these inputs:

Title / Author / Year	USBN	WSBN
The Outline of History / H. G. Wells / 1949	UAZJA136WFYXF	WC17225YANQAM
The Outline of History / H. G. Wells / 1961	UQHJ8P28DXHRC	WC17225YANQAM
George Washington A Biography / Douglas Southall Freeman / 1949	UVKK6DS3YWESM	WGVKGH0WKR66C
College Calculus with Analytic Geometry / Murray H. Protter / 1964	UGM4Y9KZVGYH7	WDYNK8KP7FHSG
Über die Relativitätstheorie / Albert Einstein / 1916	URAYHF9EDXKGQ	W718QV0NXA405
The Elements of Style / William Strunk Jr. and E. B. White / 1959	U4TMJP8GE1DSF	W4NPQT7637D53

URI scheme

USBNs and WSBNs MAY be represented as URNs:

urn:usbn:UAZJA136WFYXF
urn:wsbn:WC17225YANQAM

Or as HTTP URIs via the reference resolver (planned):

https://openusbn.org/UAZJA136WFYXF
https://openusbn.org/WC17225YANQAM

Security considerations

USBN has no security requirements. The hash function is used for compactness and determinism, not for authentication or confidentiality. An attacker who can construct metadata producing a chosen USBN gains no advantage, as USBNs carry no authority or access rights.