Develop Reference

C# getting error on decrypting byte[] from a file

I wrote this code to encrypt a text and write the encrypted text to a file and then decrypt it from the file. But I get this exception: System.Security.Cryptography.CryptographicException: 'The input data is not a complete block.' When I use a byte[] for storing data, it works perfect but it seems that it cant correctly convert a file to byte[]. I also tried File.ReadAllBytes but I got the same error. Please Help me.
class Program
{
static void Main(string[] args)
{
string decrypted;
byte[] encrypted;
Console.Write("Enter a text to encrypt : ");
string plaintext = Console.ReadLine();
using (Aes aes = Aes.Create())
{
encrypted = AesEncryption.Encrypt(plaintext, aes);
File.WriteAllText(#"C:\Users\sepita\Desktop\My.txt", Encoding.UTF8.GetString(encrypted), Encoding.UTF8);
decrypted = AesEncryption.Decrypt(Encoding.UTF8.GetBytes(File.ReadAllText(#"C:\Users\sepita\Desktop\My.txt")), aes);
}
Console.WriteLine($"Encrypted : {Encoding.UTF8.GetString(encrypted)}");
Console.WriteLine($"Decrypted : {decrypted}");
}
}
static class AesEncryption
{
public static byte[] Encrypt(string plaintext, Aes aes)
{
byte[] encrypted;
ICryptoTransform encryptor = aes.CreateEncryptor();
using (MemoryStream memoryStream = new MemoryStream())
{
using (CryptoStream stream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
{
using (StreamWriter writer = new StreamWriter(stream))
{
writer.Write(plaintext);
}
encrypted = memoryStream.ToArray();
}
}
return encrypted;
}
public static string Decrypt(byte[] encrypted, Aes aes)
{
string decrypted = null;
ICryptoTransform decryptor = aes.CreateDecryptor();
using (MemoryStream memoryStream = new MemoryStream(encrypted))
{
using (CryptoStream stream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
{
using (StreamReader reader = new StreamReader(stream))
{
decrypted = reader.ReadToEnd();
}
}
}
return decrypted;
}
}

The result of your Encrypt function is binary data. It would be pure luck if this were a valid UTF8 string, so Encoding.UTF8.GetString(encrypted) will not work in general.
Replacing it by
File.WriteAllBytes(#"C:\Users\sepita\Desktop\My.bin", encrypted);
decrypted = AesEncryption.Decrypt(File.ReadAllBytes(#"C:\Users\sepita\Desktop\My.bin"), aes);
will work.
If you want a text file, use BASE64 conversion on the binary data:
File.WriteAllText(#"C:\Users\sepita\Desktop\My.txt", Convert.ToBase64String(encrypted));
decrypted = AesEncryption.Decrypt(Convert.FromBase64String(File.ReadAllText(#"C:\Users\sepita\Desktop\My.txt")), aes);

Unrecognized unicode result from AES decryption

I try to build simple AES encryption helper to encrypt/decrypt some strings
Fist, I have an issue with Padding mode wherein decryption it only accepts if Zero otherwise an error about padding occurs!
The second issue is when I try to encrypt simple string "Hello World," it got encrypted, and I have the base64 string, but when trying to decrypt, there's no error, but a weird unknown character is shown! like 㡲啁䎰廾ử靱힩㡲啁䎰廾ử靱힩
My code:
private static int keySizes = 256;
private static int blockSize = 128;
private static PaddingMode pMode = PaddingMode.Zeros;
private static CipherMode cMode = CipherMode.ECB;
private static byte[] key = GenEncryptionKey();
private const string passphrase = #"StartYourMorningWithASmile";
private static byte[] GenEncryptionKey()
{
HashAlgorithm hash = MD5.Create();
return hash.ComputeHash(Encoding.Unicode.GetBytes(passphrase));
}
private static AesManaged CreateCryptor()
{
AesManaged cryptor = new AesManaged();
cryptor.KeySize = keySizes;
cryptor.BlockSize = blockSize;
cryptor.Padding = pMode;
cryptor.Key = key;
cryptor.Mode = cMode;
cryptor.GenerateIV();
return cryptor;
}
public static string EncryptParams(string reqVal)
{
string cipherText = "";
if (string.IsNullOrEmpty(reqVal) || reqVal.Length < 1)
throw new ArgumentNullException();
byte[] plainBytes = Encoding.Unicode.GetBytes(reqVal);
using (var cryptor = CreateCryptor())
{
ICryptoTransform encryptor = cryptor.CreateEncryptor();
using (MemoryStream ms = new MemoryStream())
{
using (CryptoStream cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
{
cs.Write(plainBytes, 0, plainBytes.Length);
}
byte[] cipherBytes = ms.ToArray();
cipherText = Convert.ToBase64String(cipherBytes);
}
cryptor.Clear();
}
return cipherText;
}
public static string DecryptParams(string resVal)
{
var data = Convert.FromBase64String(resVal);
byte[] cipherBytes = new byte[data.Length];
string plainText = "";
using (var crypto = CreateCryptor())
{
ICryptoTransform Dec = crypto.CreateDecryptor();
using (MemoryStream ms = new MemoryStream())
{
using (var cs = new CryptoStream(ms, Dec, CryptoStreamMode.Write))
{
cs.Write(cipherBytes, 0, cipherBytes.Length);
plainText = Encoding.Unicode.GetString(ms.ToArray());
}
}
crypto.Clear();
}
return plainText;
}

UPDATE 1:
Please set also the IV yourself to achieve successful decryption, as #maarten-bodewes pointed out. I missed that part and the decryption somehow worked (?) with your existing code, but you always should provide the same key and IV to a symmetric encryption algorithm to have it work both ways.
ORIGINAL ANSWER:
Your decryption fails (produces incorrect results) because you implemented the decryption part incorrectly (by using CryptoStreamMode.Write instead of CryptoStreamMode.Read) and besides feeding the decryption stream all zero bytes
At the point of execution of
cs.Write(cipherBytes, 0, cipherBytes.Length);
the variable cipherBytes is all zero. The real encrypted buffer is in the data variable which you only use to set the length of cipherBytes
So change your decryption method to this.
BONUS: After correcting the decryption part, you can specify the padding as you wish! I tested with PKCS7 and it is ok.
public static string DecryptParams(string resVal)
{
var cipherBytes = Convert.FromBase64String(resVal);
string plainText = "";
using (var crypto = CreateCryptor())
{
ICryptoTransform Dec = crypto.CreateDecryptor();
using (MemoryStream ms = new MemoryStream(cipherBytes))
{
using (var cs = new CryptoStream(ms, Dec, CryptoStreamMode.Read))
{
byte[] decryptBlock = new byte[4096];
MemoryStream decryptStream = new MemoryStream();
int readBytes;
while ((readBytes = cs.Read(decryptBlock, 0, 4096)) > 0)
{
decryptStream.Write(decryptBlock, 0, readBytes);
}
plainText = Encoding.Unicode.GetString(decryptStream.ToArray());
}
}
crypto.Clear();
}
return plainText;
}
Hope this helps.

Thanks to Oguz
Below is my description method after edit
public static string DecryptParams(string resVal)
{
var data = Convert.FromBase64String(resVal);
byte[] cipherBytes = new byte[data.Length];
string plainText = "";
using (var crypto = CreateCryptor())
{
ICryptoTransform Dec = crypto.CreateDecryptor();
using (MemoryStream ms = new MemoryStream(data))
{
using (var cs = new CryptoStream(ms, Dec, CryptoStreamMode.Read))
{
cs.Read(cipherBytes, 0, cipherBytes.Length);
plainText = Encoding.Unicode.GetString(cipherBytes.ToArray());
}
}
crypto.Clear();
}
return plainText;
}
one more thing about the return result after the decryption I got the original string plus \0\0\0\0 so I use myString.TrimEnd('\0') to solve that.

C# Encryption using RijndaelManaged - Save file in base64 format

Scenario - I have multiple files on my server and as per policy we can keep only encrypted files. We are doing some data migration, for this we have to move these files on to cloud and as per documentations Base64 is the best way to transfer encrypted data over network. I am new in encryption and stuck between this. Let me know if this help you.
How to save file in base64 format?
================================================================
I am new in Encryption and got below code from net and trying to encrypting files using RijndaelManaged and the following code is working fine
public static void EncryptFile(string inputFile, string outputFile)
{
try
{
string password = #"myKey123"; // Your Key Here
UnicodeEncoding UE = new UnicodeEncoding();
byte[] key = UE.GetBytes(password);
string cryptFile = outputFile;
FileStream fsCrypt = new FileStream(cryptFile, FileMode.Create);
RijndaelManaged RMCrypto = new RijndaelManaged();
CryptoStream cs = new CryptoStream(fsCrypt,
RMCrypto.CreateEncryptor(key, key),
CryptoStreamMode.Write);
FileStream fsIn = new FileStream(inputFile, FileMode.Open);
int data;
while ((data = fsIn.ReadByte()) != -1)
cs.WriteByte((byte)data);
fsIn.Close();
cs.Close();
fsCrypt.Close();
}
catch
{
}
}
When I try to decrypt using Convert.FromBase64String, it returns an error
public static string DecryptFile(string inputFile)
{
var myRijndael = new RijndaelManaged { Key = _key, IV = _key, Padding = PaddingMode.PKCS7 };
_decryptor = myRijndael.CreateDecryptor(myRijndael.Key, myRijndael.IV);
// Create the streams used for decryption.
using (MemoryStream msDecrypt = new MemoryStream(Convert.FromBase64String(inputFile)))
{
using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, _decryptor, CryptoStreamMode.Read))
{
using (StreamReader srDecrypt = new StreamReader(csDecrypt))
{
return srDecrypt.ReadToEnd();
}
}
}
}
Please help me to solve this issue

Encrypting and Decrypting a file with AES generates a broken file

I'm trying to encrypt and decrypt a file using AES. The problem that I have is that when the file gets decrypted, it is broken and you can't open it. The original file has a length of 81.970 bytes and the decrypted file has a length of 81.984 bytes...so there are 14 bytes added for some reason. The problem could be in the way the file gets encrypted but I don't know what I'm doing wrong.
What am I missing here? Could it be the way I'm processing the password, the iv and the padding?
Thanks for your time!
This is the code I use to encrypt:
private AesManaged aesManaged;
private string filePathToEncrypt;
public Encrypt(AesManaged aesManaged, string filePathToEncrypt)
{
this.aesManaged = aesManaged;
this.filePathToEncrypt = filePathToEncrypt;
}
public void DoEncryption()
{
byte[] cipherTextBytes;
byte[] textBytes = File.ReadAllBytes(this.filePathToEncrypt);
using(ICryptoTransform encryptor = aesManaged.CreateEncryptor(aesManaged.Key, aesManaged.IV))
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("EncryptedFile.aes", cipherTextBytes);
}
This is the code I use to decrypt:
private AesManaged aesManaged;
private string filePathToDecrypt;
public Decrypt(AesManaged aesManaged, string filePathToDecrypt)
{
this.aesManaged = aesManaged;
this.filePathToDecrypt = filePathToDecrypt;
}
public void DoDecrypt()
{
byte[] cypherBytes = File.ReadAllBytes(this.filePathToDecrypt);
byte[] clearBytes = new byte[cypherBytes.Length];
ICryptoTransform encryptor = aesManaged.CreateDecryptor(aesManaged.Key, aesManaged.IV);
using (MemoryStream ms = new MemoryStream(cypherBytes))
using (CryptoStream cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Read))
{
cs.Read(clearBytes, 0, clearBytes.Length);
clearBytes = ms.ToArray();
}
File.WriteAllBytes("DecryptedFile.gif", clearBytes);
}
And here is how I call the functions:
string filePathToEncrypt = "dilbert.gif";
string filePathToDecrypt = "EncryptedFile.aes";
string password = "Password";
string passwordSalt = "PasswordSalt";
Rfc2898DeriveBytes deriveBytes = new Rfc2898DeriveBytes(password, Encoding.ASCII.GetBytes(passwordSalt));
var aesManaged = new AesManaged
{
Key = deriveBytes.GetBytes(128 / 8),
IV = deriveBytes.GetBytes(16),
Padding = PaddingMode.PKCS7
};
Console.WriteLine("Encrypting File...");
var encryptor = new Encrypt(aesManaged, filePathToEncrypt);
encryptor.DoEncryption();
Thread.Sleep(300);
Console.WriteLine("Decrypting File...");
var decryptor = new Decrypt(aesManaged, filePathToDecrypt);
decryptor.DoDecrypt();
Thread.Sleep(300);

Try with:
public void DoEncryption()
{
byte[] cipherBytes;
byte[] textBytes = File.ReadAllBytes(this.filePathToEncrypt);
using (ICryptoTransform encryptor = aesManaged.CreateEncryptor(aesManaged.Key, aesManaged.IV))
using (MemoryStream input = new MemoryStream(textBytes))
using (MemoryStream output = new MemoryStream())
using (CryptoStream cs = new CryptoStream(output, encryptor, CryptoStreamMode.Write))
{
input.CopyTo(cs);
cs.FlushFinalBlock();
cipherBytes = output.ToArray();
}
File.WriteAllBytes("EncryptedFile.aes", cipherBytes);
}
and
public void DoDecrypt()
{
byte[] cypherBytes = File.ReadAllBytes(this.filePathToDecrypt);
byte[] textBytes;
using (ICryptoTransform decryptor = aesManaged.CreateDecryptor(aesManaged.Key, aesManaged.IV))
using (MemoryStream input = new MemoryStream(cypherBytes))
using (MemoryStream output = new MemoryStream())
using (CryptoStream cs = new CryptoStream(input, decryptor, CryptoStreamMode.Read))
{
cs.CopyTo(output);
textBytes = output.ToArray();
}
File.WriteAllBytes("DecryptedFile.gif", textBytes);
}
Note that the code could be modified to not use temporary byte[] and read/write directly to input/output streams.
In general you can't desume the length of the plaintext from the length of the cyphertext, so this line:
new byte[cypherBytes.Length]
was totally wrong.
And please, don't use Encoding.ASCII in 2016. It is so like previous century. Use Encoding.UTF8 to support non-english characters.

The answer may be very simple. I don't see where do u try to choose a cipher mode, so by default it probably takes CBC, as IV was inited. Then, 81.970 are padded by 14 bytes, to be divisible by 32. So when it happens, the memory you allocated was just 81.970, so the padding bytes doesn't write correctly, cause of some sort of memory leak, and when decrypt is started, unpadding doesn't work correctly.

Encrypting a struct, bad data error, what's causing that?

I'm not sure what I'm doing wrong, the encryption it seems to work but when you get to the decryption says bad data when trying to deserialize it, not sure what I'm doing wrong. I'm new at doing encryption so if it's something really simple I'm sorry.
public byte[] Serialize(object obj, string key)
{
byte[] returnBytes;
using (MemoryStream memory = new MemoryStream())
{
UTF8Encoding UTF8 = new UTF8Encoding();
TripleDESCryptoServiceProvider crypt = new TripleDESCryptoServiceProvider();
MD5CryptoServiceProvider provider = new MD5CryptoServiceProvider();
byte[] pass = provider.ComputeHash(UTF8.GetBytes(key));
crypt.Key = pass;
crypt.Mode = CipherMode.ECB;
crypt.Padding = PaddingMode.PKCS7;
using (CryptoStream stream = new CryptoStream(memory, crypt.CreateEncryptor(), CryptoStreamMode.Write))
{
BinaryFormatter formatter = new BinaryFormatter();
formatter.Serialize(stream, obj);
stream.Close();
memory.Close();
}
returnBytes = memory.ToArray();
}
return returnBytes;
}
public object Deserialize(byte[] inBytes, string key)
{
object returnObj;
using (MemoryStream memory = new MemoryStream())
{
UTF8Encoding UTF8 = new UTF8Encoding();
TripleDESCryptoServiceProvider crypt = new TripleDESCryptoServiceProvider();
MD5CryptoServiceProvider provider = new MD5CryptoServiceProvider();
byte[] pass = provider.ComputeHash(UTF8.GetBytes(key));
crypt.Key = pass;
crypt.Mode = CipherMode.ECB;
crypt.Padding = PaddingMode.PKCS7;
using (CryptoStream stream = new CryptoStream(memory, crypt.CreateDecryptor(), CryptoStreamMode.Read))
{
BinaryFormatter formatter = new BinaryFormatter();
returnObj = formatter.Deserialize(stream);
stream.Close();
memory.Close();
}
return returnObj;
}
}
This code i did a while back works on strings
public string encrypt(string message, string password)
{
byte[] result;
UTF8Encoding UTF8 = new UTF8Encoding();
MD5CryptoServiceProvider provider = new MD5CryptoServiceProvider();
byte[] key = provider.ComputeHash(UTF8.GetBytes(password));
TripleDESCryptoServiceProvider algorithm = new TripleDESCryptoServiceProvider();
algorithm.Key = key;
algorithm.Mode = CipherMode.ECB;
algorithm.Padding = PaddingMode.PKCS7;
byte[] data = UTF8.GetBytes(message);
try
{
ICryptoTransform encryptor = algorithm.CreateEncryptor();
result = encryptor.TransformFinalBlock(data, 0, data.Length);
}
finally
{
algorithm.Clear();
provider.Clear();
}
return Convert.ToBase64String(result);
}
public string decrypt(string message, string passsword)
{
byte[] result;
UTF8Encoding UTF8 = new UTF8Encoding();
MD5CryptoServiceProvider provider = new MD5CryptoServiceProvider();
byte[] key = provider.ComputeHash(UTF8.GetBytes(passsword));
TripleDESCryptoServiceProvider algorithm = new TripleDESCryptoServiceProvider();
algorithm.Key = key;
algorithm.Mode = CipherMode.ECB;
algorithm.Padding = PaddingMode.PKCS7;
byte[] data = Convert.FromBase64String(message);
try
{
ICryptoTransform decryptor = algorithm.CreateDecryptor();
result = decryptor.TransformFinalBlock(data, 0, data.Length);
}
finally
{
algorithm.Clear();
provider.Clear();
}
return UTF8.GetString(result);
}

You're not setting the IV property of crypt, so it's starting off as a random value each time. You need to set it to the same value when decrypting as when encrypting - like a salt for hashing. EDIT: Given the way ECB works, it looks like the IV may be ignored, which is why your previous code worked without storing it.
EDIT: While the IV part is certainly required for non-ECB, it's not enough. I'm not sure what the rest of the problem is, although:
The ECB cipher mode isn't recommended - any reason for using it?
You may well end up running into problems due to padding; I don't know if BinaryFormatter handles that for you automatically, but it's worth looking into.
EDIT: Doh - I've worked out the bigger problem; you should indeed be using inBytes, as per Elian's comment. Currently you're completely ignoring the cipher-text - that's got no chance of working!
Here's a complete program showing the whole thing hanging together:
using System;
using System.IO;
using System.Text;
using System.Security.Cryptography;
using System.Runtime.Serialization.Formatters.Binary;
class Test
{
static void Main()
{
byte[] data = Serialize("Some arbitrary test data", "pass");
object x = Deserialize(data, "pass");
Console.WriteLine(x);
}
private static SymmetricAlgorithm CreateCryptoServiceProvider(string key)
{
byte[] passwordHash;
using (MD5 md5 = MD5.Create())
{
// It's not clear why you're taking the hash of the password...
passwordHash = md5.ComputeHash(Encoding.UTF8.GetBytes(key));
}
var crypt = new TripleDESCryptoServiceProvider();
crypt.Key = passwordHash;
crypt.Mode = CipherMode.CBC; // This is the default anyway - can remove
crypt.Padding = PaddingMode.PKCS7; // Ditto
// Fix this to use a randomly generated one and store it for real code.
crypt.IV = new byte[crypt.BlockSize / 8];
return crypt;
}
public static byte[] Serialize(object obj, string key)
{
var provider = CreateCryptoServiceProvider(key);
using (MemoryStream memory = new MemoryStream())
{
using (CryptoStream stream = new CryptoStream(
memory, provider.CreateEncryptor(), CryptoStreamMode.Write))
{
BinaryFormatter formatter = new BinaryFormatter();
formatter.Serialize(stream, obj);
}
return memory.ToArray();
}
}
public static object Deserialize(byte[] inBytes, string key)
{
var provider = CreateCryptoServiceProvider(key);
using (MemoryStream memory = new MemoryStream(inBytes))
{
using (CryptoStream stream = new CryptoStream(
memory, provider.CreateDecryptor(), CryptoStreamMode.Read))
{
BinaryFormatter formatter = new BinaryFormatter();
return formatter.Deserialize(stream);
}
}
}
}