Develop Reference

C# AES Encryption Need

I have an Encrypted string and function to decrypt it. Now I need to edit this string and encrypt it. When I use this function to encrypt and decrypt in result strings are not the same.
Orginal encrypted string:
APpuC6G3f3cUKaAuOFXOGIo9rwz/+fQ0tBCi6Fk40THVnIT+au7JXkOQHdgPcpQ3VUrXw69rIL+QRsHea5+Q6TxOeuAnzkU8c3UClx6Toe+jOIVi3DlkLIGzE8DmyBArtZYpKTOt4rrOSDyLKifdgcM+MgwuJbDXyXVuQyp2C42zZ1ETPUOF2TSIZKhnMSR43FFy8WEbpKBAjkPmgVpqqhrjabu+JHbj7kPIxGGjDHGaCCyCtFwsk3264Lv4GTp049SCjNNYV0NVcN4wV0MaWMEO0iLuNGkseHuu5Snvp3YzZfXxDBWSLOUXc2zeXL2tA6So9WA5P3lZ/ga5i366EQ==
Orginal encrypted string after decrypt:
{"status":"PASS","data":{"map_path":"VOtKu0.yGT","file_extension":"KAmXWV","username":"damianek","timestamp":9999999999},"message":"Logged in successfully. Your license will run out at 2021-12-03 18:41:39"}
Orginal decrypt function:
public static string Decypher(string var1)
{
var1 = var1.Trim();
byte[] array = Convert.FromBase64String(var1);
byte[] array2 = new byte[16];
byte[] array3 = new byte[32];
byte[] array4 = new byte[array.Length - 48];
for (int i = 0; i < 16; i++)
{
array2[i] = array[i];
}
for (int j = 16; j < 48; j++)
{
array3[j - 16] = array[j];
}
for (int k = 48; k < array.Length; k++)
{
array4[k - 48] = array[k];
}
ivv = array2;
Aes aes = Aes.Create();
aes.Mode = CipherMode.CBC;
aes.Key = GetToken();
aes.IV = array2;
MemoryStream memoryStream = new MemoryStream();
ICryptoTransform transform = aes.CreateDecryptor();
CryptoStream cryptoStream = new CryptoStream(memoryStream, transform, CryptoStreamMode.Write);
string result = string.Empty;
try
{
cryptoStream.Write(array4, 0, array4.Length);
cryptoStream.FlushFinalBlock();
byte[] array5 = memoryStream.ToArray();
result = Encoding.ASCII.GetString(array5, 0, array5.Length);
memoryStream.Close();
cryptoStream.Close();
}
catch (Exception ex)
{
MessageBox.Show(ex.StackTrace);
}
return result;
}
My encrypt function:
public void EncryptStringToBytes()
{
string plainText = textBox2.Text;
byte[] array = Encoding.UTF8.GetBytes(plainText);
byte[] encrypted;
using (Aes aesAlg = Aes.Create())
{
aesAlg.Key = GetToken();
aesAlg.IV = new byte[16];
aesAlg.Mode = CipherMode.CBC;
var encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);
using (var msEncrypt = new MemoryStream())
{
using (var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
{
using (var swEncrypt = new StreamWriter(csEncrypt))
{
swEncrypt.Write(plainText);
}
encrypted = msEncrypt.ToArray();
}
}
}
textBox3.Text = Convert.ToBase64String(encrypted);
}
String after my encrypt & decrypt with orginal function:
?%j>]???r?????":"KAmXWV","username":"damianek","timestamp":1637955589},"message":"Logged in successfully. Your license will run out at 2021-12-03 18:41:39"}
EDIT:
Now encrypt function look:
public void EncryptStringToBytes()
{
string plainText = textBox2.Text.Trim();
byte[] array = Encoding.ASCII.GetBytes(plainText);
byte[] encrypted;
using (Aes aesAlg = Aes.Create())
{
aesAlg.Key = GetToken();
aesAlg.IV = GetIV();
aesAlg.Mode = CipherMode.CBC;
var encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);
using (var msEncrypt = new MemoryStream())
{
msEncrypt.Write(aesAlg.Key, 0, aesAlg.Key.Length);
msEncrypt.Flush();
using (var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
{
csEncrypt.Write(aesAlg.Key, 0, aesAlg.Key.Length);
using (var swEncrypt = new StreamWriter(csEncrypt))
{
swEncrypt.Write(plainText);
}
encrypted = msEncrypt.ToArray();
}
}
}
textBox3.Text = Convert.ToBase64String(encrypted);
}
But string after encrypt & decrypt look:
;???En Dp??g???{"status":"PASS","data":{"map_path":"VOtKu0.yGT","file_extension":"KAmXWV","username":"damianek","timestamp":1637955589},"message":"Logged in successfully. Your license will run out at 2021-12-03 18:41:39"}

My C# AES implementation
from my answer AES Crypto C# compatible Java
The IV is randomized in every Encrypt process to get different output with same text and avoid to intruders/attackers get original text easily.
The default mode is CBC.
The encoding used is UTF-8. UTF-8 is the most widely used encoding on the web.
You can test/run this code on https://replit.com/#JomaCorpFX/AesCbcEncrypt#main.cs
The code
using System;
using System.Security.Cryptography;
using System.Text;
public enum HashAlgorithm
{
MD5,
SHA1,
SHA256,
SHA384,
SHA512
}
public class HashManager
{
public static byte[] ToRawHash(byte[] data, HashAlgorithm algorithm)
{
byte[] hash;
switch (algorithm)
{
case HashAlgorithm.MD5:
MD5 md5 = MD5.Create();
hash = md5.ComputeHash(data, 0, data.Length);
return hash;
case HashAlgorithm.SHA1:
SHA1Managed sha1 = new SHA1Managed();
hash = sha1.ComputeHash(data);
return hash;
case HashAlgorithm.SHA256:
SHA256Managed sha256 = new SHA256Managed();
hash = sha256.ComputeHash(data);
return hash;
case HashAlgorithm.SHA384:
SHA384Managed sha384 = new SHA384Managed();
hash = sha384.ComputeHash(data);
return hash;
case HashAlgorithm.SHA512:
SHA512Managed sha512 = new SHA512Managed();
hash = sha512.ComputeHash(data, 0, data.Length);
return hash;
default:
throw new ArgumentException("Invalid Algorithm");
}
}
}
public class AesManager
{
private const int MAX_IV_LENGTH = 16;
private const int MAX_KEY_LENGTH = 32;
private static byte[] GenerateValidKey(byte[] keyBytes)
{
byte[] ret = new byte[MAX_KEY_LENGTH];
byte[] hash = HashManager.ToRawHash(keyBytes, HashAlgorithm.SHA256);
Array.Copy(hash, ret, MAX_KEY_LENGTH);
return ret;
}
public static byte[] EncryptRaw(byte[] PlainBytes, byte[] Key)
{
AesManaged AesAlgorithm = new AesManaged()
{
Key = GenerateValidKey(Key)
};
AesAlgorithm.GenerateIV();
var Encrypted = AesAlgorithm.CreateEncryptor().TransformFinalBlock(PlainBytes, 0, PlainBytes.Length);
byte[] ret = new byte[Encrypted.Length + MAX_IV_LENGTH];
Array.Copy(Encrypted, ret, Encrypted.Length);
Array.Copy(AesAlgorithm.IV, 0, ret, ret.Length - MAX_IV_LENGTH, MAX_IV_LENGTH);
return ret;
}
public static byte[] DecryptRaw(byte[] CipherBytes, byte[] Key)
{
AesManaged AesAlgorithm = new AesManaged()
{
Key = GenerateValidKey(Key)
};
byte[] IV = new byte[MAX_IV_LENGTH];
Array.Copy(CipherBytes, CipherBytes.Length - MAX_IV_LENGTH, IV, 0, MAX_IV_LENGTH);
AesAlgorithm.IV = IV;
byte[] RealBytes = new byte[CipherBytes.Length - MAX_IV_LENGTH];
Array.Copy(CipherBytes, RealBytes, CipherBytes.Length - MAX_IV_LENGTH);
return AesAlgorithm.CreateDecryptor().TransformFinalBlock(RealBytes, 0, RealBytes.Length); ;
}
public static String EncryptToBase64(String Plaintext, String Key)
{
byte[] PlainBytes = Encoding.UTF8.GetBytes(Plaintext);
return Base64Manager.ToBase64(EncryptRaw(PlainBytes, Encoding.UTF8.GetBytes(Key)), false);
}
public static String DecryptFromBase64(String CipherText, String Key)
{
byte[] CiPherBytes = Base64Manager.Base64ToByteArray(CipherText);
byte[] Encrypted = DecryptRaw(CiPherBytes, Encoding.UTF8.GetBytes(Key));
return Encoding.UTF8.GetString(Encrypted, 0, Encrypted.Length);
}
}
public class Base64Manager
{
public static byte[] Base64ToByteArray(String base64)
{
return Convert.FromBase64String(base64);
}
public static String ToBase64(byte[] data, Boolean insertLineBreaks = default(Boolean))
{
return insertLineBreaks ? Convert.ToBase64String(data, Base64FormattingOptions.InsertLineBreaks) : Convert.ToBase64String(data);
}
}
public class Program
{
public static void Main()
{
Console.Write("Plain text: ");
string plainText = Console.ReadLine();
Console.Write("Password: ");
string password = Console.ReadLine();
string encrypted = AesManager.EncryptToBase64(plainText, password);
Console.WriteLine();
Console.WriteLine($"Password: {password}" );
Console.WriteLine();
Console.WriteLine($"Encrypted: {encrypted}");
Console.WriteLine();
Console.WriteLine($"Decrypted: {AesManager.DecryptFromBase64(encrypted, password)}");
Console.ReadLine();
}
}
Output

How can I encrypt text with aesKey and private cert in C#?

I created public and private keys (pem) with openSsl tool. I used commands:
openssl genrsa -out privatekey.pem 2048
openssl req -new -key privatekey.pem -x509 -days 3650 -out publiccert.pem
Then I generate aesKey:
byte[] GenerateAesKey()
{
var rnd = new RNGCryptoServiceProvider();
var b = new byte[16];
rnd.GetNonZeroBytes(b);
return b;
}
My method for encrypt data:
string CreateSecurePayload(byte[] aesKey)
{
object obj = new
{
contact = new
{
email = "myName#email.com",
firstName = "John",
lastName = "Doe"
}
};
var json = Newtonsoft.Json.JsonConvert.SerializeObject(obj);
var res = "";
using (Aes myRijndael = Aes.Create())
{
byte[] encrypted = EncryptStringToBytes(json, aesKey, myRijndael.IV);
res = Convert.ToBase64String(encrypted);
}
return res;
}
byte[] EncryptStringToBytes(string plainText, byte[] Key, byte[] IV)
{
byte[] encrypted;
using (Aes rijAlg = Aes.Create())
{
rijAlg.Key = Key;
rijAlg.IV = IV;
ICryptoTransform encryptor = rijAlg.CreateEncryptor(rijAlg.Key, rijAlg.IV);
using (var msEncrypt = new MemoryStream())
{
using (var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
{
using (var swEncrypt = new StreamWriter(csEncrypt))
{
swEncrypt.Write(plainText);
}
encrypted = msEncrypt.ToArray();
}
}
}
return encrypted;
}
And then I encrypt my aesKey with private key:
string SecureKey(byte[] aesKey)
{
byte[] plainTextBytes = aesKey;
AsymmetricCipherKeyPair keys;
FileStream fileStream = new FileStream("path/to/privatekey.pem", FileMode.Open);
using (var reader = new StreamReader(fileStream))
{
var pr = new PemReader(reader);
keys = (AsymmetricCipherKeyPair)pr.ReadObject();
}
var eng = new OaepEncoding(new RsaEngine());
eng.Init(true, keys.Private);
int length = plainTextBytes.Length;
int blockSize = eng.GetInputBlockSize();
var cipherTextBytes = new List<byte>();
for (int chunkPosition = 0;
chunkPosition < length;
chunkPosition += blockSize)
{
int chunkSize = Math.Min(blockSize, length - chunkPosition);
cipherTextBytes.AddRange(eng.ProcessBlock(
plainTextBytes, chunkPosition, chunkSize
));
}
return Convert.ToBase64String(cipherTextBytes.ToArray());
}
Call methods:
void Main()
{
var aesKey = GenerateAesKey();
var encryptData = Newtonsoft.Json.JsonConvert.SerializeObject(new
{
securePayload = CreateSecurePayload(aesKey),
secureKey = SecureKey(aesKey)
});
}
I have a problem. Service does not decrypt my data with public key. I upload public key earlier in service.
Could you help me? Thanks
And I have examples of how I can encrypt data but in other languages:
I got the example, but on JS. I think I have a problem with IV, because I don`t send it

Here is the class that help you to perform Encryption/Decryption:
public static class DecryptionHelper
{
private static string EncryptionDecryptionKey = "your_key";
public static string Encrypt(string Text)
{
//var key = GenerateKey();
var key = Encoding.UTF8.GetBytes(EncryptionDecryptionKey);
var plainText = Text;
var encryptedData = EncryptStringToBytes(key, plainText);
return Convert.ToBase64String(encryptedData);
}
public static string Decrypt(string Text)
{
//var key = GenerateKey();
var key = Encoding.UTF8.GetBytes(EncryptionDecryptionKey);
byte[] encryptedData = Convert.FromBase64String(Text);
var decryptedData = DecryptBytesToString(key, encryptedData);
return decryptedData;
}
private static string DecryptBytesToString(byte[] key, byte[] data)
{
// IV was prepended to the encrypted bytes so peel that off
Tuple<byte[], byte[]> splitResult = SplitByteArray(data);
byte[] iv = splitResult.Item1;
byte[] cipherText = splitResult.Item2;
// Declare the string used to hold the decrypted text.
string plaintext;
// Create an RijndaelManaged object
// with the specified key and IV.
using (var aes = CreateAes256Algorithm())
{
aes.Key = key;
aes.IV = iv;
// Create a decrytor to perform the stream transform.
ICryptoTransform decryptor = aes.CreateDecryptor(aes.Key, aes.IV);
// Create the streams used for decryption.
using (var msDecrypt = new MemoryStream(cipherText))
{
using (var csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
{
using (var srDecrypt = new StreamReader(csDecrypt))
{
// Read the decrypted bytes from the decrypting stream
// and place them in a string.
plaintext = srDecrypt.ReadToEnd();
}
}
}
}
return plaintext;
}
private static Tuple<byte[], byte[]> SplitByteArray(byte[] data)
{
byte[] first = new byte[16];
Buffer.BlockCopy(data, 0, first, 0, first.Length);
byte[] second = new byte[data.Length - first.Length];
Buffer.BlockCopy(data, first.Length, second, 0, second.Length);
return Tuple.Create(first, second);
}
private static byte[] GenerateKey()
{
using (var aes = CreateAes256Algorithm())
{
aes.GenerateKey();
return aes.Key;
}
}
private static RijndaelManaged CreateAes256Algorithm()
{
return new RijndaelManaged { KeySize = 256, BlockSize = 128 };
}
private static byte[] EncryptStringToBytes(byte[] key, string plainText)
{
byte[] encrypted;
byte[] iv;
// Create an RijndaelManaged object with the specified key and IV.
using (var aes = CreateAes256Algorithm())
{
aes.Key = key;
aes.GenerateIV();
iv = aes.IV;
// Create a encrytor to perform the stream transform.
ICryptoTransform encryptor = aes.CreateEncryptor(aes.Key, aes.IV);
// Create the streams used for encryption.
using (var msEncrypt = new MemoryStream())
{
using (var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
{
using (var swEncrypt = new StreamWriter(csEncrypt))
{
//Write all data to the stream.
swEncrypt.Write(plainText);
}
// convert stream to bytes
encrypted = msEncrypt.ToArray();
}
}
}
// Prepend the iV to the encrypted bytes
return CombineByteArrays(iv, encrypted);
}
private static byte[] CombineByteArrays(byte[] first, byte[] second)
{
byte[] ret = new byte[first.Length + second.Length];
Buffer.BlockCopy(first, 0, ret, 0, first.Length);
Buffer.BlockCopy(second, 0, ret, first.Length, second.Length);
return ret;
}
}
Then to use it like:
Keys.FacebookClientId = DecryptionHelper.Decrypt(FacebookClientId);

using System;
using System.Text;
using Org.BouncyCastle.OpenSsl;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Engines;
using Org.BouncyCastle.Crypto.Encodings;
using System.Security.Cryptography;
using System.IO;
public static string CreateSecureLoad(string unencryptedPayload, ref byte[] generatedAesKey)
{
// This method generates and returns a secure payload ​
RijndaelManaged cryptoAlgo = new RijndaelManaged
{
Padding = PaddingMode.PKCS7,
Mode = CipherMode.ECB,
KeySize = 128,
BlockSize = 128
};​
generatedAesKey = cryptoAlgo.Key;
var clearTextArray = Encoding.UTF8.GetBytes(unencryptedPayload);
var encryptor = cryptoAlgo.CreateEncryptor();​
using (MemoryStream msEncrypt = new MemoryStream())
{
using (CryptoStream csEncrypt = new CryptoStream(
msEncrypt,
encryptor,
CryptoStreamMode.Write))
{
csEncrypt.Write(clearTextArray);
csEncrypt.FlushFinalBlock();
var cipher = msEncrypt.ToArray();
return Convert.ToBase64String(cipher);
}
}
}
public static string CreateSecureKey(byte[] aesKey, string privateKeyPEM)
{
// This method generates and returns a secure key
// Accepts the string contents of the private key PEM file as input
​
var encryptEngine = new Pkcs1Encoding(new RsaEngine());
​
using (var textReader = new StringReader(privateKeyPEM))
{
var pemReader = new PemReader(textReader);
var keyPair = (AsymmetricCipherKeyPair)pemReader.ReadObject();
encryptEngine.Init(true, keyPair.Private);
}
​
var encrypted = Convert.ToBase64String(
encryptEngine.ProcessBlock(
aesKey,
0,
aesKey.Length));
return encrypted;
}
static void Main(string[] args)
{
String payload = "some json";
​
byte[] generatedAesKey = new byte[16];
var privateKeyPEM = File.ReadAllText("privatekey.pem");
​
var securePayload = CreateSecureLoad(payload, ref generatedAesKey);
var secureKey = CreateSecureKey(generatedAesKey, privateKeyPEM);
​
// Return encrypted key
Console.WriteLine("secureKey: " + secureKey);
​
// Return encrypted payload
Console.WriteLine("securePayload: " + securePayload);​
Console.ReadLine();​
}
}

'Padding is invalid and cannot be removed.'

encryption in this way works fine but when i try to use Decrypt it gives me padding Error i don't know why ?? Here is main Method and used Key & IV Value.
& BaseEncryptor Class Where i Use Encryption & Decryption Method
I tried uesing every type in padding but it also doesn't work.I tried to change block size and key size it also doesn't work.
static void Main(string[] args)
{
string key = "ldm_encrypt_code1234567891234567";
string IV = "9876897123651785";
string encstr = BaseEncryptor.EncryptUsingAes(Encoding.UTF8.GetBytes(#"Hello Code"), Encoding.UTF8.GetBytes(key), Encoding.UTF8.GetBytes(IV)); //Encryption
string xc=BaseEncryptor.Decrypt(Encoding.UTF8.GetBytes(encstr), Encoding.UTF8.GetBytes(key), Encoding.UTF8.GetBytes(IV)); //Decryption way
}
public class BaseEncryptor
{
public static string EncryptUsingAes(byte[] inputTextByte, byte[] privateKeyByte, byte[] sharedIVKeyByte)
{
using (var aesEncryption = AesEncryptionType(privateKeyByte, sharedIVKeyByte))
{
// Convert string to byte array
byte[] dest = new byte[inputTextByte.Length];
// encryption
using (ICryptoTransform encrypt = aesEncryption.CreateEncryptor(aesEncryption.Key, aesEncryption.IV))
{
dest = encrypt.TransformFinalBlock(inputTextByte, 0, inputTextByte.Length);
encrypt.Dispose();
}
return BitConverter.ToString(dest).Replace("-", "");
}
}
public static AesCryptoServiceProvider AesEncryptionType(byte[] privateKeyByte, byte[] sharedIVKeyByte)
{
//used in both encryption & Decryption
var aes = new AesCryptoServiceProvider();
aes.BlockSize = 128;
aes.KeySize = 256;
aes.IV = sharedIVKeyByte;
aes.Key = privateKeyByte;
aes.Mode = CipherMode.CBC; //Mode
aes.Padding = PaddingMode.PKCS7; //Padding not working in case of none or Zeros
return aes;
}
public static string DecryptUsingAes(byte[] inputTextByte, byte[] privateKeyByte, byte[] sharedIVKeyByte)
{
using (var aesDecryption = AesEncryptionType(privateKeyByte, sharedIVKeyByte))
{
// Convert string to byte array
byte[] dest = new byte[inputTextByte.Length];
// encryption
using (ICryptoTransform decrypt = aesDecryption.CreateDecryptor(aesDecryption.Key, aesDecryption.IV))
{
dest = decrypt.TransformFinalBlock(inputTextByte, 0, inputTextByte.Length);
decrypt.Dispose();
}
// Convert byte array to UTF8 string
return Encoding.UTF8.GetString(dest); ;
}
}
public static string Decrypt(byte[] cipherText, byte[] Key, byte[] IV)
{
string plaintext = null;
// Create AesManaged
using (var aesDecryption = AesEncryptionType(Key, IV))
{
// Create a decryptor
// Create the streams used for decryption.
using (ICryptoTransform decryptor = aesDecryption.CreateDecryptor(Key, IV))
{
string result;
using (var msDecrypt = new MemoryStream(cipherText))
{
using (var csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
{
using (var srDecrypt = new StreamReader(csDecrypt))
{
result = srDecrypt.ReadToEnd();
}
}
}
}
return plaintext;
}
}
}

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.

AESManaged File Encryption and Decryption and prepending initiaization vector

I am trying to encrypt/decrypt bytes - I have done a lot of reading about the Key and IV for the AES algorithm using the AESManaged class in System.Security.Cryptography. I read James Johnson's answer to the following question http://www.techques.com/question/1-7025135/My-Length-of-the-data-to-decrypt-is-invalid-error where he suggests that you use a random IV in the encryption routine and prepend the IV to the encrypted message. The decrypt function strips off the random IV from the beginning of the encrypted message to initialize the decryption class and then decrypts the rest of the bytes. I have attempted to do this in the following code. But I keep getting the "Length of the data to decrypt is invalid." error message when I attempt the decrypt after the encryption. Could someone possibly shed some light on what might be wrong.
USAGE: (streamToEncrypt/streamToDecrypt are System.IO.Stream)
using (var cryptoHelper = new AESHelper())
{
var encryptedBytes = cryptoHelper.Encrypt(AESHelper.StreamToByteArray(streamToEncrypt));
}
using (var cryptoHelper = new AESHelper())
{
var decryptedBytes = cryptoHelper.Decrypt(AESHelper.StreamToByteArray(streamToDecrypt));
}
public class AESHelper : IDisposable
{
public AesManaged AESManaged;
internal ICryptoTransform Encryptor { get; set; }
internal ICryptoTransform Decryptor { get; set; }
private const string KEY = "2428GD19569F9B2C2341839416C8E87G";
private static readonly byte[] Salt = Encoding.ASCII.GetBytes("?pt1$8f]l4g80");
private const Int32 ITERATIONS = 1042;
internal AESHelper()
{
AESManaged = new AesManaged();
AESManaged.BlockSize = AESManaged.LegalBlockSizes[0].MaxSize;
AESManaged.KeySize = AESManaged.LegalKeySizes[0].MaxSize;
AESManaged.Mode= CipherMode.CBC;
}
public void KeyGenerator()
{
var key = new Rfc2898DeriveBytes(KEY, Salt, ITERATIONS);
AESManaged.Key = key.GetBytes(AESManaged.KeySize / 8);
}
public byte[] Encrypt(byte[] input)
{
KeyGenerator();
var ms = new MemoryStream();
//Random IV
Encryptor = AESManaged.CreateEncryptor(AESManaged.Key, AESManaged.IV);
//Add the IV to the beginning of the memory stream
ms.Write(BitConverter.GetBytes(AESManaged.IV.Length), 0, sizeof(int));
ms.Write(AESManaged.IV, 0, AESManaged.IV.Length);
var cs = new CryptoStream(ms,
Encryptor, CryptoStreamMode.Write);
cs.Write(input, 0, input.Length);
cs.Close();
return ms.ToArray();
}
public byte[] Decrypt(byte[] input)
{
KeyGenerator();
// Get the initialization vector from the encrypted stream
var ms = new MemoryStream(input);
AESManaged.IV = ReadByteArray(ms);
Decryptor = AESManaged.CreateDecryptor(AESManaged.Key, AESManaged.IV);
var cs = new CryptoStream(ms,
Decryptor, CryptoStreamMode.Write);
cs.Write(input, 0, input.Length);
cs.Close();//Error occurs here
return ms.ToArray();
}
internal static byte[] ReadByteArray(Stream s)
{
var rawLength = new byte[sizeof(int)];
if (s.Read(rawLength, 0, rawLength.Length) != rawLength.Length)
{
throw new SystemException("Stream did not contain properly formatted byte array");
}
var buffer = new byte[16];
if (s.Read(buffer, 0, buffer.Length) != buffer.Length)
{
throw new SystemException("Did not read byte array properly");
}
return buffer;
}
internal static byte[] StreamToByteArray(Stream inputStream)
{
if (!inputStream.CanRead)
{
throw new ArgumentException();
}
// This is optional
if (inputStream.CanSeek)
{
inputStream.Seek(0, SeekOrigin.Begin);
}
var output = new byte[inputStream.Length];
var bytesRead = inputStream.Read(output, 0, output.Length);
Debug.Assert(bytesRead == output.Length, "Bytes read from stream matches stream length");
return output;
}
public void Dispose()
{
if (AESManaged != null)
((IDisposable) AESManaged).Dispose();
}}
Many Thanks in advance

Probably you have solved this already but I'll just put my answer for others who faces similar issue.
Error occurs due to the additional information present in the input array. In public byte[] Encrypt(byte[] input) method you are writing IV length and IV before the ciphered data is written. Lines:
ms.Write(BitConverter.GetBytes(AESManaged.IV.Length), 0, sizeof(int));
ms.Write(AESManaged.IV, 0, AESManaged.IV.Length);
In public byte[] Decrypt(byte[] input) method you are reading this information and using read IV as initialization vector for AES algorithm. All fine. Then you are constructing CryptoStream with CryptoStreamMode.Write and passing MemoryStream object ms which gets decrypted data. However the passed input array contains not only the encrypted message but also the IV that you wrote during the encryption process. That is why it fails to decrypt.
What you need to do to overcome this is either extract only cipher data from the input array and pass it to: cs.Write(cipherData, 0, cipherData.Length); or change mode into CryptoStreamMode.Read and use cs.Read(outputBuff, 0, outputBuff.Length);.
Also don't use the same MemoryStream object to read and write to because you'll have some garbage in it after CryptoStream will write in it.