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How to encrypt / decrypt binary data in .NET 6.0 with AES in C#?

I'm trying to encrypt binary data with AES in .Net 6.0. Unfortunately, the decryption does not bring back the original data:
public static byte[] Encrypt(byte[] plainBytes)
{
using (var aes = System.Security.Cryptography.Aes.Create())
{
byte[] cipherBytes;
using (MemoryStream cipherStream = new MemoryStream())
using (CryptoStream cryptoStream = new CryptoStream(cipherStream, aes.CreateEncryptor(aes.Key, aes.IV), CryptoStreamMode.Write))
{
cryptoStream.Write(plainBytes, 0, plainBytes.Length);
cryptoStream.FlushFinalBlock();
cipherStream.Seek(0, SeekOrigin.Begin);
cipherBytes = new byte[cipherStream.Length];
cipherStream.Read(cipherBytes, 0, cipherBytes.Length);
}
byte[] wrongPlainBytes;
using (MemoryStream cipherStream = new MemoryStream(cipherBytes))
using (CryptoStream cryptoStream = new CryptoStream(cipherStream, aes.CreateDecryptor(aes.Key, aes.IV), CryptoStreamMode.Read))
{
wrongPlainBytes = cipherStream.ToArray();
}
bool shouldBeTrue = plainBytes.Equals(wrongPlainBytes);
return cipherBytes;
}
}
After executing this code, shouldBeTrue should be true, but it's false. Also, plainBytes.Length is different from wrongPlainBytes.Length.
What do I wrong while encryption / decryption?

public static byte[] Encrypt( byte[] plainBytes )
{
using ( var aes = System.Security.Cryptography.Aes.Create() )
{
byte[] cipherBytes;
using ( MemoryStream cipherStream = new MemoryStream() )
using ( CryptoStream cryptoStream = new CryptoStream( cipherStream, aes.CreateEncryptor( aes.Key, aes.IV ), CryptoStreamMode.Write ) )
{
cryptoStream.Write( plainBytes, 0, plainBytes.Length );
cryptoStream.FlushFinalBlock();
cipherBytes = cipherStream.ToArray();
}
byte[] wrongPlainBytes;
using ( MemoryStream cipherStream = new MemoryStream() )
using ( CryptoStream cryptoStream = new CryptoStream( cipherStream, aes.CreateDecryptor( aes.Key, aes.IV ), CryptoStreamMode.Write ) )
{
cryptoStream.Write( cipherBytes, 0, cipherBytes.Length );
cryptoStream.FlushFinalBlock();
wrongPlainBytes = cipherStream.ToArray();
}
bool shouldBeTrue = plainBytes.SequenceEqual( wrongPlainBytes );
return cipherBytes;
}
}

Try to avoid direct Read on streams where possible - this operation is not guaranteed to read the amount of bytes you requested, so when you do use it - you need to check the return value (which you ignore) to figure out actual number of bytes that were read, and then act accordingly (do more reads if that amount is less than what you need).
There are several issues in your code, which you can avoid this way:
public static byte[] Encrypt(byte[] plainBytes)
{
using (var aes = System.Security.Cryptography.Aes.Create())
{
byte[] cipherBytes;
using (MemoryStream cipherStream = new MemoryStream()) {
// use leaveOpen parameter here, that way it will NOT dispose cipherStream when closing cryptoStream
using (CryptoStream cryptoStream = new CryptoStream(cipherStream, aes.CreateEncryptor(aes.Key, aes.IV), CryptoStreamMode.Write, true)) {
// just write
cryptoStream.Write(plainBytes, 0, plainBytes.Length);
}
// now, cryptoStream is disposed, so we can be sure all data is propertly written to the cipherStream
// no need to flush or anything
// do not manage buffer yourself, use ToArray
cipherBytes = cipherStream.ToArray();
}
byte[] wrongPlainBytes;
using (MemoryStream cipherStream = new MemoryStream(cipherBytes)) {
using (CryptoStream cryptoStream = new CryptoStream(cipherStream, aes.CreateDecryptor(aes.Key, aes.IV), CryptoStreamMode.Read)) {
using (var output = new MemoryStream()) {
// same story here, avoid direct reads, use CopyTo, it will copy all data, decrypted, to memory stream
cryptoStream.CopyTo(output);
// again, just ToArray to avoid manage buffer directly
wrongPlainBytes = output.ToArray();
}
}
}
bool shouldBeTrue = plainBytes.SequenceEqual(wrongPlainBytes);
return cipherBytes;
}
}

C# Encryption System.Security.Cryptography.CryptographicException at CryptoStream.close()

im trying to write an En-/Decrypter in C#. As the title suggests I get a System.Security.Cryptography.CryptographicException at CryptoStream.close(). I haven't find a solution yet. Hope anyone can help.
public static string viaRijndael(byte[] input, string key, string iV)
{
Rijndael RijCrypt = Rijndael.Create();
RijCrypt.Key = System.Text.Encoding.UTF8.GetBytes(Tools.GetMD5Hash(Tools.GetMD5Hash(key)));
RijCrypt.IV = System.Text.Encoding.UTF8.GetBytes(Tools.GetMD5Hash(Tools.GetMD5Hash(key)).Substring(0, 16));
MemoryStream ms = new MemoryStream();
CryptoStream cs = new CryptoStream(ms, RijCrypt.CreateDecryptor(), CryptoStreamMode.Write);
cs.Write(input, 0, input.Length);
cs.Close(); // System.Security.Cryptography.CryptographicException
byte[] DecryptedBytes = ms.ToArray();
return System.Text.Encoding.UTF8.GetString(DecryptedBytes);
}

MSDN Stream.Close documentation says:
"This method calls Dispose, specifying true to release all resources. You do not have to specifically call the Close method. Instead, ensure that every Stream object is properly disposed. You can declare Stream objects within a using block (or Using block in Visual Basic) to ensure that the stream and all of its resources are disposed, or you can explicitly call the Dispose method."
As such I would suggest trying something like the following to handle the disposal of your streams:
public static string viaRijndael(byte[] input, string key, string iV)
{
byte[] decryptedBytes;
using (Rijndael rijCrypt = Rijndael.Create())
{
rijCrypt.Key = System.Text.Encoding.UTF8.GetBytes(Tools.GetMD5Hash(Tools.GetMD5Hash(key)));
rijCrypt.IV = System.Text.Encoding.UTF8.GetBytes(Tools.GetMD5Hash(Tools.GetMD5Hash(key)).Substring(0, 16));
using (MemoryStream ms = new MemoryStream())
{
using (CryptoStream cs = new CryptoStream(ms, rijCrypt.CreateDecryptor(), CryptoStreamMode.Write))
{
cs.Write(input, 0, input.Length);
}
decrpytedBytes = ms.ToArray();
}
}
return System.Text.Encoding.UTF8.GetString(decryptedBytes);
}
All of this and more is explained in good detail on MSDN for the CryptoStream class.

C# CryptographicException length of the data to decrypt is invalid

I have this code which is meant to decrypt a file, but if I run it, it throws a CryptographicException (length of the data to decrypt is invalid) at the end of the using statement using (CryptoStream ...) { ... }
public static void DecryptFile(string path, string key, string saltkey, string ivkey)
{
try
{
byte[] cipherTextBytes;
using (StreamReader reader = new StreamReader(path)) cipherTextBytes = Encoding.UTF8.GetBytes(reader.ReadToEnd());
byte[] keyBytes = new Rfc2898DeriveBytes(key, Encoding.ASCII.GetBytes(saltkey)).GetBytes(256 / 8);
RijndaelManaged symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC, Padding = PaddingMode.None };
ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, Encoding.ASCII.GetBytes(ivkey));
byte[] plainTextBytes;
using (MemoryStream memoryStream = new MemoryStream(cipherTextBytes))
{
using (CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
{
plainTextBytes = new byte[Encoding.UTF8.GetByteCount((new StreamReader(cryptoStream)).ReadToEnd())];
cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
//plainTextBytes = memoryStream.ToArray();
cryptoStream.FlushFinalBlock();
}
}
string result = Encoding.ASCII.GetString(plainTextBytes, 0, plainTextBytes.Length).TrimEnd("\0".ToCharArray());
using (FileStream writer = new FileStream(path, FileMode.Create)) writer.Write(Encoding.ASCII.GetBytes(result), 0, Encoding.ASCII.GetBytes(result).Length);
MessageBox.Show("Decrypt succesfull");
}
catch (Exception ex)
{
MessageBox.Show("An error while decrypting the file:\n\n" + ex, "Error");
}
}
}
Does anybody know why this is or how I can fix it? (I don't know if it comes from my encrypting method, but I have another program which uses the exact same thing to encrypt strings and that one does work.)
My encrypting method:
public static void EncryptFile(string path, string key, string saltkey, string ivkey)
{
try
{
byte[] TextBytes;
using (StreamReader reader = new StreamReader(path)) TextBytes = Encoding.UTF8.GetBytes(reader.ReadToEnd());
byte[] KeyBytes = new Rfc2898DeriveBytes(key, Encoding.ASCII.GetBytes(saltkey)).GetBytes(256 / 8);
RijndaelManaged symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC, Padding = PaddingMode.Zeros };
ICryptoTransform encryptor = symmetricKey.CreateEncryptor(KeyBytes, Encoding.ASCII.GetBytes(ivkey));
byte[] CipherTextBytes;
using (MemoryStream ms = new MemoryStream())
{
using (CryptoStream cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
{
cs.Write(TextBytes, 0, TextBytes.Length);
cs.FlushFinalBlock();
CipherTextBytes = ms.ToArray();
}
}
using (FileStream writer = new FileStream(path, FileMode.Create)) writer.Write(CipherTextBytes, 0, CipherTextBytes.Length);
MessageBox.Show("Encrypt succesfull");
}
catch (Exception ex)
{
MessageBox.Show("An error while encrypting the file:\n\n" + ex, "Error");
}
}

There are a few issues with your code:
You use a padding mode of Zeroes in Encrypt and None in Decrypt. These need to match
You load the bytes from your file using Encoding.UTF8, you need to read the raw bytes, you can do this by using the following instead:
byte[] cipherTextBytes = File.ReadAllBytes(path);
You call cryptoStream.FlushFinalBlock(); when only using a single iteration of a stream. You don't need this call in Decrypt if you are only doing a single block iteration.
You read the original text from your file in UTF8 and then write it back as ASCII. You should either change the result assignment in decrypt to use UTF8 or (preferably) change both to use raw bytes.
You use Create to interact with the files when you are overwriting in-place. If you know the file already exists (as you are replacing it) you should use truncate or better yet just call File.WriteAllBytes.
Your decrypt is all kinds of messed up. It looks like you're tying yourself into knots over byte retrieval. You should just use the raw bytes out of the CryptoStream and not try using UTF8
Here's a revised set of methods for you:
public static void DecryptFile(string path, string key, string saltkey, string ivkey)
{
byte[] cipherTextBytes = File.ReadAllBytes(path);
byte[] keyBytes = new Rfc2898DeriveBytes(key, Encoding.ASCII.GetBytes(saltkey)).GetBytes(256 / 8);
RijndaelManaged symmetricKey = new RijndaelManaged() { Mode = CipherMode.CFB, Padding = PaddingMode.PKCS7 };
ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, Encoding.ASCII.GetBytes(ivkey));
byte[] plainTextBytes;
const int chunkSize = 64;
using (MemoryStream memoryStream = new MemoryStream(cipherTextBytes))
using (MemoryStream dataOut = new MemoryStream())
using (CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
using (var decryptedData = new BinaryReader(cryptoStream))
{
byte[] buffer = new byte[chunkSize];
int count;
while ((count = decryptedData.Read(buffer, 0, buffer.Length)) != 0)
dataOut.Write(buffer, 0, count);
plainTextBytes = dataOut.ToArray();
}
File.WriteAllBytes(path, plainTextBytes);
}
and:
public static void EncryptFile(string path, string key, string saltkey, string ivkey)
{
byte[] TextBytes = File.ReadAllBytes(path);
byte[] KeyBytes = new Rfc2898DeriveBytes(key, Encoding.ASCII.GetBytes(saltkey)).GetBytes(256 / 8);
RijndaelManaged symmetricKey = new RijndaelManaged() { Mode = CipherMode.CFB, Padding = PaddingMode.PKCS7 };
ICryptoTransform encryptor = symmetricKey.CreateEncryptor(KeyBytes, Encoding.ASCII.GetBytes(ivkey));
byte[] CipherTextBytes;
using (MemoryStream ms = new MemoryStream())
using (CryptoStream cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
{
cs.Write(TextBytes, 0, TextBytes.Length);
cs.FlushFinalBlock();
CipherTextBytes = ms.ToArray();
}
File.WriteAllBytes(path, CipherTextBytes);
}

Most likely your problem comes from cipherTextBytes = Encoding.UTF8.GetBytes(reader.ReadToEnd());
You can't use UTF8 to encode arbitrary binary data, you will likely need to fix both your encrypting end decrypting end. You either must use cipherTextBytes = File.ReadAllBytes(path) or if you are forced to use strings you must first encode the bytes to a valid string using Convert.ToBase64String()

In my case it happened because I was decrypting a value which was never encrypted.
I had my values saved in the database without encryption. But when I introduced encryption and decryption routine in my code and executed my program first time, it was actually trying to decrypt a value which was never encrypted, hence the problem.
Simply clearing the existing values from the database for the initial run solved the problem. If you don't want to lose data even during the first run then you should write a separate routine to encrypt the existing values.

RijndaelManaged doesn't encrypt

I'm trying to encrypt a buffer with RijndaelManaged class without any success. It always return byte[0]. Here's the code:
public byte[] Encrypt(byte[] data, byte[] key)
{
using (var ms = new MemoryStream())
{
using (var aes = RijndaelManaged.Create())
{
aes.Key = _checksumProvider.CalculateChecksum(key);
aes.IV = _checksumProvider.CalculateChecksum(key);
var stream = new CryptoStream(ms, aes.CreateEncryptor(aes.Key, aes.IV), CryptoStreamMode.Write);
stream.Write(data, 0, data.Length);
return ms.ToArray();
}
}
}
Key and IV are correctly assigned. Any idea what's wrong with the code? Thanks.

You need to call stream.FlushFinalBlock().
This will perform any final steps in the encryption, and flush the CryptoStream's internal buffer into the underlying memory stream.

Padding is invalid and cannot be removed Exception while decrypting string using "AesManaged" C#

Please suggest me where i need to update/refactor the code to get rid of exception. I am getting exception while I try to decrypt the encrypted string using following code.
Following line is throwing exception
using (StreamReader srDecrypt = new StreamReader(csDecrypt))
{
// Read the decrypted bytes from the decrypting stream
// and place them in a string.
plaintext = srDecrypt.ReadToEnd();
}
public string EncryptAuthenticationTokenAes(string plainText)
{
byte[] encrypted;
// Create an AesManaged object
// with the specified key and IV.
using (AesManaged aesAlg = new AesManaged())
{
// Create a decrytor to perform the stream transform.
ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);
aesAlg.Padding = PaddingMode.None;
// Create the streams used for encryption.
using (MemoryStream msEncrypt = new MemoryStream())
{
using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
{
using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
{
//Write all data to the stream.
swEncrypt.Write(plainText);
}
encrypted = msEncrypt.ToArray();
}
}
}
// Return the encrypted bytes from the memory stream.
return Convert.ToBase64String(encrypted);
}
public string DecryptPasswordAes(string encryptedString)
{
//Convert cipher text back to byte array
byte[] cipherText = Convert.FromBase64String(encryptedString);
// Declare the string used to hold
// the decrypted text.
string plaintext = null;
// Create an AesManaged object
// with the specified key and IV.
using (AesManaged aesAlg = new AesManaged())
{
// Create a decrytor to perform the stream transform.
ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);
aesAlg.Padding = PaddingMode.None;
// Create the streams used for decryption.
using (MemoryStream msDecrypt = new MemoryStream(cipherText))
{
using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
{
using (StreamReader srDecrypt = new StreamReader(csDecrypt))
{
// Read the decrypted bytes from the decrypting stream
// and place them in a string.
plaintext = srDecrypt.ReadToEnd();
}
}
}
}
return plaintext;
}

Pretty standard bug when using CryptoStream, you forgot to force it to encrypt the last bytes of the stream. It keeps bytes in an internal buffer until enough of them arrive to emit a block. You must force the last few bytes out. Fix:
using (var msEncrypt = new MemoryStream())
using (var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
using (var swEncrypt = new StreamWriter(csEncrypt)) {
swEncrypt.Write(plainText);
csEncrypt.FlushFinalBlock();
encrypted = msEncrypt.ToArray();
}
You got the exception when decrypting it because encrypted is missing the final padding. The real problem is caused by the using statement, you wouldn't have this problem if you waited obtaining the encrypted bytes until after the CryptoStream is closed. But that doesn't work well because the using statement on the StreamWriter also closes the CryptoStream and the MemoryStream. Explicitly using FlushFinalBlock() is the best workaround.