Added iteration upgrading for streams

Encrypter Tests/EncrypterTests.cs

@@ -168,6 +168,81 @@ namespace Encrypter_Tests
             }
         }
 
+        [Test]
+        public async Task TestUpgradedIterationsBehaviourStreaming()
+        {
+            var tempFileInput = Path.GetTempFileName();
+            var tempFileEncryptedPrevious = Path.GetTempFileName();
+            var tempFileReEncrypted = Path.GetTempFileName();
+            var tempFileDecrypted = Path.GetTempFileName();
+
+            try
+            {
+                var message = "This is a test with umlauts äüö.";
+                await File.WriteAllTextAsync(tempFileInput, message);
+
+                var password = "test password";
+                var previousIterations = 1_000;
+                var upgradedIterations = 1_000_000;
+
+                await using (var outputStream = File.OpenWrite(tempFileEncryptedPrevious))
+                {
+                    await using var inputStream = File.OpenRead(tempFileInput);
+                    await CryptoProcessor.Encrypt(inputStream, outputStream, password, previousIterations);
+                }
+
+                await using (var outputStream = File.OpenWrite(tempFileReEncrypted))
+                {
+                    await using var inputStream = File.OpenRead(tempFileEncryptedPrevious);
+                    await CryptoProcessor.UpgradeIterations(inputStream, outputStream, password, previousIterations, upgradedIterations);
+                }
+                
+                Assert.That(await File.ReadAllBytesAsync(tempFileEncryptedPrevious), Is.Not.EqualTo(await File.ReadAllBytesAsync(tempFileReEncrypted)));
+
+                await using (var outputStream = File.OpenWrite(tempFileDecrypted))
+                {
+                    await using var inputStream = File.OpenRead(tempFileReEncrypted);
+                    await CryptoProcessor.Decrypt(inputStream, outputStream, password, upgradedIterations);
+                }
+                
+                Assert.That(await File.ReadAllTextAsync(tempFileDecrypted), Is.EqualTo(message));
+            }
+            finally
+            {
+                try
+                {
+                    File.Delete(tempFileInput);
+                }
+                catch
+                {
+                }
+
+                try
+                {
+                    File.Delete(tempFileDecrypted);
+                }
+                catch
+                {
+                }
+
+                try
+                {
+                    File.Delete(tempFileEncryptedPrevious);
+                }
+                catch
+                {
+                }
+
+                try
+                {
+                    File.Delete(tempFileReEncrypted);
+                }
+                catch
+                {
+                }
+            }
+        }
+
         [Test]
         public async Task TestChangedPasswordBehaviour()
         {

Encrypter/CryptoProcessor.cs

@@ -319,6 +319,45 @@ namespace Encrypter
             return await CryptoProcessor.Encrypt(decryptedData, password, upgradedIterations);
         }
 
+        /// <summary>
+        /// Upgrades the encryption regarding the used iterations for the key. In order to re-encrypt the stream, a temporary file
+        /// gets used. When the returned task is finished, the re-encryption is done as well.
+        /// </summary>
+        /// <param name="inputStreamBeforeUpgrade">The encrypted data with the previous settings.</param>
+        /// <param name="outputStreamUpgraded">The re-encrypted data.</param>
+        /// <param name="password">The password.</param>
+        /// <param name="previousIterations">The previous number of iterations.</param>
+        /// <param name="upgradedIterations">The upgraded number of iterations.</param>
+        public static async Task UpgradeIterations(Stream inputStreamBeforeUpgrade, Stream outputStreamUpgraded, string password, int previousIterations, int upgradedIterations)
+        {
+            var tempFileCache = Path.GetTempFileName();
+
+            try
+            {
+                await using (var tempCacheStream = File.OpenWrite(tempFileCache))
+                {
+                    // Decrypt the data with the previous settings:
+                    await Decrypt(inputStreamBeforeUpgrade, tempCacheStream, password, previousIterations);
+                }
+
+                await using (var tempCacheStream = File.OpenRead(tempFileCache))
+                {
+                    // Encrypt the data with the new settings:
+                    await Encrypt(tempCacheStream, outputStreamUpgraded, password, upgradedIterations);
+                }
+            }
+            finally
+            {
+                try
+                {
+                    File.Delete(tempFileCache);
+                }
+                catch
+                {
+                }
+            }
+        }
+
         /// <summary>
         /// Changes the password of the encryption.
         /// </summary>

Encrypter/Encrypter.xml

@@ -75,6 +75,17 @@
             <param name="upgradedIterations">The upgraded number of iterations.</param>
             <returns>The re-encrypted data.</returns>
         </member>
+        <member name="M:Encrypter.CryptoProcessor.UpgradeIterations(System.IO.Stream,System.IO.Stream,System.String,System.Int32,System.Int32)">
+            <summary>
+            Upgrades the encryption regarding the used iterations for the key. In order to re-encrypt the stream, a temporary file
+            gets used. When the returned task is finished, the re-encryption is done as well.
+            </summary>
+            <param name="inputStreamBeforeUpgrade">The encrypted data with the previous settings.</param>
+            <param name="outputStreamUpgraded">The re-encrypted data.</param>
+            <param name="password">The password.</param>
+            <param name="previousIterations">The previous number of iterations.</param>
+            <param name="upgradedIterations">The upgraded number of iterations.</param>
+        </member>
         <member name="M:Encrypter.CryptoProcessor.ChangePassword(System.String,System.String,System.String,System.Int32)">
             <summary>
             Changes the password of the encryption.