Mtf.Cryptography 2.0.6

RsaCipher Class

Implements the IAsymmetricCipher interface using RSA encryption with optional OAEP padding.
Provides both string and byte-level encryption/decryption, with support for importing keys from XML files.

Namespace: Mtf.Cryptography.AsymmetricCiphers
Implements: IAsymmetricCipher, IDisposable

🔐 Features

• Uses RSA with OAEP (SHA-256) or PKCS#1 v1.5 padding
• Supports encryption with public key and decryption with private key
• Can import keys from XML files
• Exposes RSAParameters containing the public key
• Supports encryption/decryption of both byte arrays and strings (Base64 encoded)

🧩 Constructors

RsaCipher(string keyFilePath, bool includePrivateParameters = false, bool useOaepPadding = true)

Loads RSA parameters from an XML-formatted key file.

• keyFilePath: Path to the XML file
• includePrivateParameters: true to include private key parameters
• useOaepPadding: Use OAEP with SHA-256 padding (true) or PKCS#1 v1.5 (false)

RsaCipher(RSAParameters parameters, bool useOaepPadding = true)

Initializes from an RSAParameters struct.

• parameters: Must include at least Modulus and Exponent
• useOaepPadding: OAEP (SHA-256) or PKCS#1 padding

🔑 Public Properties

RSAParameters PublicKeyParameters { get; }

Contains the public portion of the RSA key (Modulus, Exponent).

🔒 Methods

byte[] Encrypt(byte[] plainBytes)

Encrypts a byte array using the configured RSA key and padding.

string Encrypt(string plainText)

Encrypts a string using UTF-8 and returns a Base64 encoded result.

byte[] Decrypt(byte[] cipherBytes)

Decrypts an RSA-encrypted byte array.
Requires that the private key is present, otherwise throws InvalidOperationException.

string Decrypt(string cipherText)

Decrypts a Base64-encoded RSA ciphertext string.
Requires private key.

♻️ Disposal

Dispose()

Releases underlying RSA resources. Safe to call multiple times.

⚠️ Exceptions

• ArgumentNullException — Input is null
• InvalidOperationException — Private key is missing for decryption
• CryptographicException — Key import or crypto failure
• FormatException — Invalid Base64 input during decryption

📦 Example Usage

var rsa = new RsaCipher("key.xml", includePrivateParameters: true);
var encrypted = rsa.Encrypt("secret message");
var decrypted = rsa.Decrypt(encrypted);