Updated program to use streams

Program.cs

@@ -1,72 +1,67 @@
 using System.Security.Cryptography;
-using System.Text;
 
-static string Encrypt(string plainText, byte[] secretKey) {
+/// <summary>
-	using Aes aes = Aes.Create();
+/// Method <c>GetAES</c> creates a custom AES object with the given key
-	aes.Key = secretKey;
+/// and IV, and also specifies the cipher mode and padding mode as
-
+/// with the supplier.
-	// Convert the plain text string into a byte array
+/// </summary>
-	byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);
+/// <param name="key">The key to use for the AES object.</param>
-
+/// <param name="iv">The initialization vector to use for the AES object.</param>
-	// Create an encryptor using the AES service and its initialization vector (IV)
+static Aes CreateAES(byte[] key, byte[] iv) {
-	ICryptoTransform encryptor = aes.CreateEncryptor(aes.Key, aes.IV);
+	Aes aes = Aes.Create(); // Create a new instance of Aes
-
+	aes.KeySize = key.Length * 8; // Key size is set to the length of the input key multiplied by 8
-	// Perform the encryption
+	aes.Key = key; // The Key and IV values are set from the parameters
-	byte[] encrypted = encryptor.TransformFinalBlock(plainTextBytes, 0, plainTextBytes.Length);
-
-	// Create a new byte array to hold the IV and the encrypted data
-	byte[] result = new byte[aes.IV.Length + encrypted.Length];
-
-	// Copy the IV and encrypted data into the result byte array
-	Buffer.BlockCopy(aes.IV,    0, result, 0,             aes.IV.Length);
-	Buffer.BlockCopy(encrypted, 0, result, aes.IV.Length, encrypted.Length);
-
-	return Convert.ToBase64String(result);
-}
-
-static string Decrypt(string encryptedText, byte[] secretKey) {
-	using Aes aes = Aes.Create();
-	aes.Key = secretKey;
-
-	// Decode the base64 string into a byte array
-	byte[] fullCipher = Convert.FromBase64String(encryptedText);
-
-	// Create byte arrays to hold the IV and the encrypted data
-	byte[] iv = new byte[aes.BlockSize / 8];
-	byte[] cipher = new byte[fullCipher.Length - iv.Length];
-
-	// Copy the IV and encrypted data from the full cipher byte array
-	Buffer.BlockCopy(fullCipher, 0, iv, 0, iv.Length);
-	Buffer.BlockCopy(fullCipher, iv.Length, cipher, 0, cipher.Length);
-
-	// Assign the IV to the AES service
 	aes.IV = iv;
-
+	aes.Mode = CipherMode.CBC; // Cipher mode is set to CBC (Cipher Block Chaining) mode
-	// Create a decryptor using the AES service
+	aes.Padding = PaddingMode.PKCS7; // Padding mode is set to PKCS7 (Public Key Cryptography Standard #7) padding
-	ICryptoTransform decryptor = aes.CreateDecryptor(aes.Key, aes.IV);
+	return aes;
-
-	// Perform the decryption
-	byte[] decrypted = decryptor.TransformFinalBlock(cipher, 0, cipher.Length);
-
-	// Convert the decrypted byte array back into a string
-	return Encoding.UTF8.GetString(decrypted);
 }
 
+/// <summary>
+/// Method <c>Encrypt</c> encrypts the given plain text using the provided AES object.
+/// </summary>
+/// <param name="plainText">The plain text to encrypt.</param>
+/// <param name="aes">The AES object to use for encryption.</param>
+/// <returns>The encrypted text as a base64 string.</returns>
+static string Encrypt(string plainText, Aes aes) {
+	using MemoryStream memoryStream = new(); // Creates a new memory stream for writing data
+	using CryptoStream cryptoStream = new(memoryStream, aes.CreateEncryptor(), CryptoStreamMode.Write); // Creates a new CryptoStream using the given Aes object and the memory stream for writing data
+	using StreamWriter streamWriter = new(cryptoStream); // Creates a new StreamWriter using the above CryptoStream
+	streamWriter.Write(plainText); // Writes the plain text to the StreamWriter
+	cryptoStream.FlushFinalBlock(); // Writes the final block of data to the CryptoStream and closes the stream
+	string output = Convert.ToBase64String(memoryStream.ToArray()); // Converts the contents of the memory stream to a byte array and returns the base64-encoded string representation of the array
+	return output; // Returns the encrypted output as a base64 string
+}
 
-Console.WriteLine("Hello, World!");
+/// <summary>
+/// Method <c>Decrypt</c> decrypts the given encrypted text using the provided AES object.
+/// </summary>
+/// <param name="encryptedText">The encrypted text to decrypt, as a Base64 string.</param>
+/// <param name="aes">The AES object to use for decryption.</param>
+/// <returns>The decrypted string, in plain-text</returns>
+static string Decrypt(string encryptedText, Aes aes) {
+	using MemoryStream memoryStream = new(Convert.FromBase64String(encryptedText)); // Creates a new memory stream using the given encrypted text, converted from a base64 string to a byte array
+	using CryptoStream cryptoStream = new(memoryStream, aes.CreateDecryptor(), CryptoStreamMode.Read); // Creates a new CryptoStream using the given AES object and the memory stream for reading data
+	using StreamReader streamReader = new(cryptoStream); // Creates a new StreamReader using the above CryptoStream
+	string output = streamReader.ReadToEnd(); // Reads the entire stream and returns the contents as a string
+	return output; // Returns the decrypted output as a string
+}
 
-string key = "REDACTED_BASE64_STRING";
+byte[] key = Convert.FromBase64String("REDCATED");
-byte[] secretKey = Convert.FromBase64String(key);
+byte[] iv  = Convert.FromBase64String("REDACTED");
+using Aes aes = CreateAES(key, iv);
 
+string plainText = "Hello, AES-CBC with PKCS7 padding!";
+string encrypted = Encrypt(plainText, aes);
+Console.WriteLine($"Encrypted text: '{encrypted}' (from '{plainText}')");
+string decrypted = Decrypt(encrypted, aes);
+Console.WriteLine($"Decrypted text: '{decrypted}' (from '{encrypted}')");
+
+Console.WriteLine();
+string secureText = "REDACTED";
 try {
-	string input = "Hello, world!";
+	string decrypted2 = Decrypt(secureText, aes);
-	Console.WriteLine("Original text: " + input);
+	Console.WriteLine($"Previously encrypted decrypted text: '{decrypted2}' (from '{secureText}')");
-
+} catch (Exception ex) {
-	string encryptedText = Encrypt(input, secretKey);
+	Console.WriteLine($"Error: {ex.Message}");
-	Console.WriteLine("Encrypted text: " + encryptedText);
-
-	string decrypted = Decrypt(encryptedText, secretKey);
-	Console.WriteLine("Decrypted text: " + decrypted);
-} catch (Exception e) {
-	Console.WriteLine(e);
 }