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)
• Two case-insensitive encodings: 32-character base32hex and 40-character hex
• More than 32,768 unique, time-ordered but unpredictable IDs per millisecond
• Nearly 111-bit randomness for collision resistance

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.

License

Copyright 2021 LiosK

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

See Also

• npm package
• API Documentation
• Run tests on your browser