scru160

SCRU-160: Sortable, Clock and Random number-based Unique identifier

SCRU-160 ID is yet another attempt to supersede UUID in the use cases that need decentralized, globally unique time-ordered identifiers. SCRU-160 is inspired by ULID and KSUID and has the following features:

• 160-bit length
• Sortable by generation time (in binary and in text)
• At least 32,767 unique, time-ordered IDs per millisecond
• Nearly 111-bit randomness for collision resistance
• 32-character base32hex encoding and 40-character hex encoding
• Case insensitive

import { scru160, scru160f } from "scru160";

console.log(scru160()); // e.g. "05TTUP1HNCPNH30VEK64KDQT9BSNU4C4"
console.log(scru160()); // e.g. "05TTUP1HNCPNIB63R8IN5V2L3VFGNFET"

console.log(scru160f()); // e.g. "017bdf6431bb33750751eb63beb3c3f8c5969d86"
console.log(scru160f()); // e.g. "017bdf6431bb337662412e6a5758890735c33c2b"

Binary Layout and Byte Order

A SCRU-160 ID is an 160-bit object that consists of the following four fields:

Bit #	Field	Data Type
Msb 0 - 47	timestamp	48-bit unsigned integer, big-endian
Msb 48 - 63	counter	16-bit unsigned integer, big-endian
Msb 64 - 79	random16	16-bit unsigned integer, big-endian
Msb 80 - 159	random80	80-bit unsigned integer, big-endian

• timestamp - Unix time in milliseconds
• counter - Reset to a 15-bit random number when timestamp changes; incremented by one for each new ID generated within the same timestamp (a different implementation may reset it to a smaller random number or zero to accommodate more IDs per millisecond)
• random16 - Random number (documented separately from random80 for future expansion)
• random80 - Random number

Cryptographically secure random number generators are employed if possible.

Encodings

The base32hex encoding as defined in RFC 4648 is used by default to produce a 32-character textual representation consisting of [0-9A-V].

scru160(); // e.g. "05TUIM8J8SU9O6P30I56PP49PI0RGNPM"

Alternatively, hexadecimal encoding can be used to produce a 40-character hex string that looks like the commonly seen SHA-1 hashes.

scru160f(); // e.g. "017be95b2d6042db903a19a0974182ec7445188a"

The base32hex representations and hex representations cannot be mixed when SCRU-160 IDs need to be lexicographically sortable.

See Also

• API Documentation
• Run tests on your browser