Class ShortCode

Generates, normalizes and formats short codes that users read on one screen and type on another, such as device link codes or setup codes: 8 characters from Crockford's base 32 (about 10^12 codes), displayed as K7PX-M3QR.

Inheritance

object

ShortCode

Namespace: Singulink.Net.Http.Api.Service.SignIn

Assembly: Singulink.Net.Http.Api.Service.dll

Syntax

public static class ShortCode

Remarks

The alphabet has the digits and the letters without I, L, O and U, so codes avoid characters that are easily confused. Typing is forgiving: case does not matter, O is read as 0, I and L are read as 1, and spaces and dashes are ignored.

Short codes can be guessed far more easily than random keys: whatever a code unlocks is exposed for as long as the code is valid, to as many wrong attempts as are allowed. There are few enough codes that a plain hash of one can be reversed by hashing every code, while a keyed hash (see ComputeHash(string, ReadOnlySpan<byte>)) cannot be without its key.

Fields

Name	Description
Length	The number of characters in a normalized code.
MinHashKeyLength	The minimum length of the key of ComputeHash(string, ReadOnlySpan<byte>), in bytes.

Methods

Name	Description
ComputeHash(string, ReadOnlySpan<byte>)	Computes the keyed hash (HMAC-SHA256) of a code, as 43 base64url characters. The code is normalized first, so typed input gives the same hash as the generated code.
Format(string)	Formats a code for display, for example K7PX-M3QR. The code is normalized first, so typed input is accepted too.
Generate()	Generates a new random code in normalized form (Length characters, without the dash).
Normalize(string)	Normalizes a code typed by a user, or returns null if the input cannot be a code. The input is case-insensitive, O is read as 0, I and L are read as 1, and spaces and dashes are ignored.