PasswordGenerator

A lightweight, secure, and flexible password generator library for .NET, built with cryptographic randomness and fully customizable character sets.

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Features

• Cryptographically secure — built on .NET’s RandomNumberGenerator for high-entropy randomness
• Performance-focused — uses Span<char> and stack allocation to minimize heap usage and avoid unnecessary string allocations
• Customizable character sets — define your own character pools (e.g., symbols, digits, uppercase)
• Per-set minimum requirements — ensure that a minimum number of characters from each set are included
• Predictable-free output — final password is securely shuffled to eliminate character order patterns
• Ambiguity-avoiding — easily exclude confusing characters like 0, O, l, and I
• Clean, testable design — .NET 8 compatible and unit-tested

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using KPasswordGenerator;

// Define your password policy
PasswordSettings settings = new(
[
    new(minRequired: 2, characterPool: "ABCDEFGHJKLMNPQRSTUVWXYZ"),
    new(3, "abcdefghijkmnopqrstuvwxyz"),   // At least 3 lowercase letters (no l)
    new(4, "23456789"),                    // At least 4 digits (no 0, 1)
    new(2, "!@$?_-")                       // At least 2 symbols
]);

PasswordGenerator generator = new(settings);

string password = generator.Generate(passwordLength: 16);

Console.WriteLine(password);  // Example output: kAj79uV@E?m7_8eS

Using WithDefaults

Quickly generate a password using default pools:

PasswordSettings settings = PasswordSettings.WithDefaults(minLower: 2, minUpper: 2, minDigits: 2, minSpecial: 1);
PasswordGenerator generator = new(settings);

string password = generator.Generate(12);

Additional Methods

GenerateRandomLength(int minPasswordLength, int maxPasswordLength)

Generates a password of random length within a specified range.

• Ensures the generated password meets all defined character requirements.
• Uses secure randomness to choose the length.

Example:

string password = generator.GenerateRandomLength(12, 20);

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Validate(string password)

Validates whether a password meets the current PasswordSettings policy.

• Checks overall length.

• Verifies that the required number of characters from each character pool are present.

• Returns true if all rules pass, otherwise false.

• Example:

bool isValid = generator.Validate("abcD123!");

Installation

Install via NuGet:

dotnet add package KPasswordGenerator