using System;

using System.IO;

using System.Security.Cryptography;

using System.Text;

​

public class EncryptionValue

{

    public int PassIterations { get; set; }

    public int KeySize { get; set; }

    public string InitVector { get; set; }

    public string SaltValue { get; set; }

}

​

​

public class Program

{

    static HashAlgorithmName hash = HashAlgorithmName.SHA256;

    public static string Decrypt(string data, EncryptionValue eV, string passPhrase)

    {

        byte[] bytes = Encoding.ASCII.GetBytes(eV.InitVector);

        byte[] rgbSalt = Encoding.ASCII.GetBytes(eV.SaltValue);

        byte[] buffer = Convert.FromBase64String(data);

        byte[] rgbKey = new Rfc2898DeriveBytes(passPhrase, rgbSalt, eV.PassIterations, hash).GetBytes(eV.KeySize / 8);

​

        var managed = Aes.Create("AesManaged");

        managed.Padding = PaddingMode.PKCS7;

        managed.Mode = CipherMode.CBC;

        ICryptoTransform transform = managed.CreateDecryptor(rgbKey, bytes);

        MemoryStream stream = new(buffer);

        CryptoStream stream2 = new(stream, transform, CryptoStreamMode.Read);

        byte[] buffer5 = new byte[buffer.Length];

        Console.WriteLine($"buffer5.Length = {buffer5.Length} bytes");

        int numberOfReadCalls = 0;

        int numberOfBytesInBuffer = 0;

        while (numberOfBytesInBuffer < buffer5.Length)

        {

            numberOfReadCalls++;

            var n = stream2.Read(buffer5, numberOfBytesInBuffer, buffer5.Length - numberOfBytesInBuffer);

            numberOfBytesInBuffer += n;

            Console.WriteLine($"Number of bytes read at stream2.Read call #{numberOfReadCalls} = {n}");

            if (n == 0) break;

        }

            Console.WriteLine($"Total amount of bytes read from CryptoStream = {numberOfBytesInBuffer}");

        int count = numberOfBytesInBuffer;

        stream.Close();

        stream2.Close();

        return Encoding.UTF8.GetString(buffer5, 0, count);

    }

​

    public static string Encrypt(string data, EncryptionValue eV, string passPhrase)

    {

        byte[] bytes = Encoding.ASCII.GetBytes(eV.InitVector);

        byte[] rgbSalt = Encoding.ASCII.GetBytes(eV.SaltValue);

        byte[] buffer = Encoding.UTF8.GetBytes(data);

        byte[] rgbKey = new Rfc2898DeriveBytes(passPhrase, rgbSalt, eV.PassIterations, hash).GetBytes(eV.KeySize / 8);

​

        Console.WriteLine($"Length of plaintext buffer to be encrypted: {buffer.Length} bytes");

        var managed = Aes.Create("AesManaged");

        managed.Padding = PaddingMode.PKCS7;

​

        managed.Mode = CipherMode.CBC;

        ICryptoTransform transform = managed.CreateEncryptor(rgbKey, bytes);

        MemoryStream stream = new();

        CryptoStream stream2 = new(stream, transform, CryptoStreamMode.Write);

        stream2.Write(buffer, 0, buffer.Length);

        stream2.FlushFinalBlock();

        byte[] inArray = stream.ToArray();

        stream.Close();

        stream2.Close();

        return Convert.ToBase64String(inArray);

    }

    public static void Main()

    {

        var ev = new EncryptionValue

        {

            InitVector = "~1B2c3D4e5F6g7H8",

            SaltValue = "SnafuFoobar",

            PassIterations = 1,

            KeySize = 256,

        };

        var plainText = "Hello world! Mouser trousers are cute. Singer songer singalong. What should i write, what can i write? About the weather? Boring. What i write is boring.";

        Console.WriteLine($"Length of plaintext: {plainText.Length} characters");

        var enc = Encrypt(plainText, ev, "foobar");

        var decrypted = Decrypt(enc, ev, "foobar");

        Console.WriteLine($"Length of decrpyted plain text: {decrypted.Length} characters");

        Console.WriteLine($"Is decrypted text equal plainText: {decrypted == plainText}");

    }

}