Add project files.

SacsStandardBase/Base/Data/SacsAesIvCrypter.cs

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+using Sarand.Net.Standard.Base.App;
+using Sarand.Net.Standard.Base.Core;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Security.Cryptography;
+using System.Text;
+
+namespace Sarand.Net.Standard.Base.Data
+{
+	//=======================================================================
+	public static class SacsAesIvCrypter
+	{
+		//-------------------------------------------------------------------
+		// Properties.
+		public static String AesIvDelimiter { get; } = ";";
+		public static String AesIvPrefix { get; } = "AESIV:";
+
+		//-------------------------------------------------------------------
+		// Ref. https://xamarinhelp.com/cryptography-in-xamarin-forms/
+		// For reversible encryption, AES is generally the recommended standard.
+		// AES 256 requires a 32 byte key to encrypt.
+		// Either generate a 32 byte key or use any string and convert it into a key with CreateKey.
+		// NB The salt will remain the same here for each key generated - it does not need to be randomized as with hashing.
+		//-------------------------------------------------------------------
+		private static byte[] CreateKey (string password, int keyBytes = 32)
+		{
+			byte[] salt = new byte[] { 80, 70, 60, 50, 40, 30, 20, 10 };
+			int iterations = 300;
+			DeriveBytes keyGenerator = new Rfc2898DeriveBytes(password, salt, iterations);
+			return keyGenerator.GetBytes(keyBytes);
+		}
+
+		//-------------------------------------------------------------------
+		// Encrypt String.
+		// Return the encrypted text with the IV appended to the end.
+		// In AES, the IV is a randomizer, making sure that no two identical messages ever give the same encrypted output.
+		// The IV can be public and does not need to be hidden.
+		//-------------------------------------------------------------------
+		public static string Encrypt (this string clearValue, string encryptionKey)
+		{
+			using (Aes aes = Aes.Create())
+			{
+				aes.Key = CreateKey(encryptionKey);
+				byte[] aesIV = aes.IV;
+				byte[] encrypted = Encrypt(clearValue, aes.Key, aesIV);
+				return Convert.ToBase64String(encrypted) + AesIvDelimiter + Convert.ToBase64String(aesIV);
+			}
+		}
+		//-------------------------------------------------------------------
+		public static byte[] Encrypt (string plainText, byte[] key, byte[] iv)
+		{
+			if (plainText == null || plainText.Length <= 0) throw new ArgumentNullException($"{nameof(plainText)}");
+			if (key == null || key.Length <= 0) throw new ArgumentNullException($"{nameof(key)}");
+			if (iv == null || iv.Length <= 0) throw new ArgumentNullException($"{nameof(iv)}");
+			byte[] encrypted;
+			using (Aes aes = Aes.Create())
+			{
+				aes.Key = key;
+				aes.IV = iv;
+				using (MemoryStream memoryStream = new MemoryStream())
+				{
+					using (ICryptoTransform encryptor = aes.CreateEncryptor())
+					using (CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
+					using (StreamWriter streamWriter = new StreamWriter(cryptoStream))
+					{
+						streamWriter.Write(plainText);
+					}
+					encrypted = memoryStream.ToArray();
+				}
+			}
+			return encrypted;
+		}
+
+		//-------------------------------------------------------------------
+		// Decrypt String.
+		// Decryption requires the encrypted value and the secret key.
+		// This function is directly related to the above encryption process and will
+		// assume that the IV is at the end of the string passed in.
+		// To decrypt a message encrypted by another function, the IV will have to be passed explicitly.
+		//-------------------------------------------------------------------
+		public static string Decrypt (this string encryptedValue, string encryptionKey)
+		{
+			String[] valueParts = encryptedValue.Split(new String[] { AesIvDelimiter }, StringSplitOptions.None);
+			if (valueParts.Length != 2)
+			{
+				SaLogger.Warn("SacsAesIvCrypter.Decrypt Missing IV - assuming not encrypted");
+				return encryptedValue;
+				//throw new CryptographicException("Decrypt failure: Missing IV");
+			}
+			return Decrypt(Convert.FromBase64String(valueParts[0]), CreateKey(encryptionKey), Convert.FromBase64String(valueParts[1]));
+		}
+		//-------------------------------------------------------------------
+		public static string Decrypt (byte[] cipherText, byte[] key, byte[] iv)
+		{
+			if (cipherText == null || cipherText.Length <= 0) throw new ArgumentNullException($"{nameof(cipherText)}");
+			if (key == null || key.Length <= 0) throw new ArgumentNullException($"{nameof(key)}");
+			if (iv == null || iv.Length <= 0) throw new ArgumentNullException($"{nameof(iv)}");
+
+			string plaintext = "";
+			using (Aes aes = Aes.Create())
+			{
+				aes.Key = key;
+				aes.IV = iv;
+				using (MemoryStream memoryStream = new MemoryStream(cipherText))
+				using (ICryptoTransform decryptor = aes.CreateDecryptor())
+				using (CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
+				using (StreamReader streamReader = new StreamReader(cryptoStream))
+					plaintext = streamReader.ReadToEnd();
+			}
+			return plaintext;
+		}
+
+		//-------------------------------------------------------------------
+	}
+	//=======================================================================
+}