KNM.CryptoHelper

Description

KNM.CryptoHelper is a C# library for AES symmetric encryption with HMAC integrity, designed to be configurable and reusable in .NET projects.

Installation

Build the project as a Class Library to generate the KNM.CryptoHelper.dll and include it in your project.

Usage

Configuration (simple)

var options = new CryptoOptions
{
	Password = "password_segreta",
	SaltSize = 16,
	IvSize = 16,
	KeySize = 32,
	Iterations = 100_000
};

var cryptoHelper = new CryptoHelper(options);

Configuration (with Injection)

Register the services in the DI collection In the ConfigureServices method of ASP.NET Core (or in the generic builder):

services.Configure<CryptoOptions>(configuration.GetSection("CryptoOptions")); // Se vuoi usare appsettings.json

services.AddSingleton<ICryptoHelper>(sp =>
{
    var options = sp.GetRequiredService<IOptions<CryptoOptions>>().Value;
    return new CryptoHelper(options);
});

Or passing a manual configuration:

var options = new CryptoOptions
{
    Password = "miaPassword",
    SaltSize = 16,
    IvSize = 16,
    KeySize = 32,
    Iterations = 100_000
};

services.AddSingleton<ICryptoHelper>(new CryptoHelper(options));

Or if you want to use default values:

services.AddSingleton<ICryptoHelper>(new CryptoHelper());

Encrypting a text

string testoChiaro = "Testo da criptare";
string testoCifrato = cryptoHelper.EncryptText(testoChiaro);
Console.WriteLine($"Testo cifrato: {testoCifrato}");

Decrypting an encrypted text

string testoDecifrato = cryptoHelper.DecryptText(testoCifrato);
Console.WriteLine($"Testo decifrato: {testoDecifrato}");

Technical details

• Encryption is AES in CBC mode with PKCS7 padding.
• The AES key is derived using PBKDF2 with SHA256.
• Message integrity is guaranteed with HMAC-SHA256.
• The encrypted string is formatted as: !HMAC:SALT:IV:CIPHERTEXT (all Base64).

Error handling

• A CryptographicException is thrown in case of tampering or wrong password.
• Incorrect input formats throw FormatException.

Notes

• For security reasons, change the default password to a strong and unique one in your environment.
• Parameters like salt size, iterations, and key size are customizable via CryptoOptions.