I am Learning C#, and are practicing with decryption and encryption.
I used the Aes Class Example from MSDN, and the encryption is working great.
However, when i am trying to decrypt the textfile, nothing happens.
I figured i had done something wrong in the decryption function, so i tested with a string instead.
The decryption worked perfect with the string So i am wondering what i am doing wrong.
This is what my encryption and decryption looks like:
//The encryption
string path = #"C:\encrypt.txt";
//The path where my .txt file is.
string textfile = File.ReadAllText(path);
//Reading the text in the file and storing it in a string.
byte[] ByteToEncrypt = EncryptStringToBytes(textfile, myAes.Key, myAes.IV);
//From The Aes class example
string encrypted = "";
//Creating a string to store the bytes in.
for (int i = 0; i < ByteToEncrypt.Length; i++)
{
encrypted = encrypted + ByteToEncrypt[i];
//Adding all the bytes from an array to string.
}
File.WriteAllText(path, encrypted, LATIN1);
//Writing the encrypted string to the .txtfile.
//The decryption
string decrypted = DecryptStringFromBytes(ByteToEncrypt, myAes.Key, myAes.IV);
//From the Aes class example.
File.WriteAllText(path, Decrypted, LATIN1);
//Writing the decrypted string to textfile.
I am posting the Aes class below for further information.
static byte[] EncryptStringToBytes(string plaintext, byte[] Key, byte[] IV)
{
//Checking the arguments
if (string.IsNullOrEmpty(plaintext))
{
throw new ArgumentNullException("plaintext");
}
else if (Key == null || Key.Length <= 0)
{
throw new ArgumentNullException("key");
}
else if (IV == null || IV.Length <= 0)
{
throw new ArgumentNullException("IV");
}
byte[] encrypted;
//Create an Aes object
//With the specified key and IV
using (Aes Aesalg = Aes.Create())
{
Aesalg.Key = Key;
Aesalg.IV = IV;
//Create a encryptor to perform the stream transform
ICryptoTransform encryptor = Aesalg.CreateEncryptor(Aesalg.Key, Aesalg.IV);
//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))
{
swEncrypt.Write(plaintext);
}
encrypted = msencrypt.ToArray();
}
}
}
return encrypted;
}
static string DecryptStringFromBytes(byte[] ciphertext, byte[] Key, byte[] IV)
{
if (ciphertext == null || ciphertext.Length <= 0)
{
throw new ArgumentNullException("plaintext");
}
else if (Key == null || Key.Length <= 0)
{
throw new ArgumentNullException("Key");
}
else if (IV == null || IV.Length <= 0)
{
throw new ArgumentNullException("IV");
}
string plaintext = null;
using (Aes Aesalg = Aes.Create())
{
Aesalg.Key = Key;
Aesalg.IV = IV;
ICryptoTransform decryptor = Aesalg.CreateDecryptor(Aesalg.Key, Aesalg.IV);
using (MemoryStream msDecrypt = new MemoryStream(ciphertext))
{
using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
{
using (StreamReader srDecrypt = new StreamReader(csDecrypt))
{
plaintext = srDecrypt.ReadToEnd();
}
}
}
}
return plaintext;
}
You cannot just add bytes to a String. Byte can have any value between 00 and FF inclusive (using hexadecimal representation). You simply seem to add those bytes as integers to the string, as
encrypted = encrypted + ByteToEncrypt[i];
simply creates a String value such as "0255" for byte values 00 and FF. Of course, you will have an issue when you try and decrypt such a string, if only because the bytes are not separated anymore.
Instead, you should create a base 64 encoding of the ciphertext after encryption, and convert it back into bytes before decrypting. Or, as ntoskrnl suggests, you can of course just treat the ciphertext as binary all the way, if that's an option.
Related
I am facing strange issue with AES encryption and getting error while decryption.
Error while decrypt:
padding is invalid and cannot be removed
Encrypt Method:
private static string Encrypt(string plainText, byte[] key)
{
// Check arguments.
if (plainText == null || plainText.Length <= 0)
throw new ArgumentNullException("plainText");
if (key == null || key.Length <= 0)
throw new ArgumentNullException("Key");
byte[] encrypted;
// Create an Aes object
// with the specified key and IV.
using (Aes aesAlg = Aes.Create())
{
Rfc2898DeriveBytes deriveBytes = new Rfc2898DeriveBytes("SharedPassword", key);
aesAlg.Key = deriveBytes.GetBytes(aesAlg.KeySize/8);
//aesAlg.IV = iv;
aesAlg.GenerateIV();
// Create a decrytor to perform the stream transform.
ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);
// 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);
}
Decrypt Method:
private static string Decrypt(string token, byte[] key)
{
byte[] cipherText = Convert.FromBase64String(token);
// Check arguments.
if (cipherText == null || cipherText.Length <= 0)
throw new ArgumentNullException("cipherText");
if (key == null || key.Length <= 0)
throw new ArgumentNullException("Key");
// Declare the string used to hold
// the decrypted text.
string plaintext = null;
// Create an Aes object
// with the specified key and IV.
using (Aes aesAlg = Aes.Create())
{
Rfc2898DeriveBytes deriveBytes = new Rfc2898DeriveBytes("SharedPassword", key);
aesAlg.Key = deriveBytes.GetBytes(aesAlg.KeySize / 8);
aesAlg.GenerateIV();
// Create a decrytor to perform the stream transform.
ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);
// 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(); // Error here
}
}
}
}
return plaintext;
}
I have tried many work around as mention below but none of them works.
AES decrypt fails with "Padding is invalid and cannot be removed"
C#: AES error: Padding is invalid and cannot be removed. Same key and everything, help
I don't get what is issue with code.
I am trying to decode an AES cipher in C#. If I use the same AES object as when I encode them, everything is fine. But as soon as I create a different instance of AES, it does not work:
string original = "username,password,companyID";
byte[] encrypted;
using (Aes myAes1 = Aes.Create()) {
encrypted = EncryptStringToBytes_Aes(original, GetBytes("password"), myAes1.IV);
//test1
string test1 = DecryptStringFromBytes_Aes(encrypted, GetBytes("password"), myAes1.IV);
}
using (Aes myAes2 = Aes.Create()) {
//test2
string test2 = DecryptStringFromBytes_Aes(encrypted, GetBytes("password"), myAes2.IV);
}
So in this code, test1 uses myAes1 and it works out fine because the encryption also used myAes1. However test2 uses myAes2 and it doesn't work, here is the output:
test1 = username,password,companyID
test2 = t0�V�e]��Ԅ��yd,companyID
what am I doing wrong?
Here are the supporting functions, which I copied from online:
static byte[] EncryptStringToBytes_Aes(string plainText, byte[] Key,byte[] IV) {
// Check arguments.
if (plainText == null || plainText.Length <= 0)
throw new ArgumentNullException("plainText");
if (Key == null || Key.Length <= 0)
throw new ArgumentNullException("Key");
if (IV == null || IV.Length <= 0)
throw new ArgumentNullException("Key");
byte[] encrypted;
// Create an Aes object
// with the specified key and IV.
using (Aes aesAlg = Aes.Create()) {
aesAlg.Key = Key;
aesAlg.IV = IV;
// Create a decrytor to perform the stream transform.
ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);
// 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 encrypted;
}
static string DecryptStringFromBytes_Aes(byte[] cipherText, byte[] Key, byte[] IV) {
// Check arguments.
if (cipherText == null || cipherText.Length <= 0)
throw new ArgumentNullException("cipherText");
if (Key == null || Key.Length <= 0)
throw new ArgumentNullException("Key");
if (IV == null || IV.Length <= 0)
throw new ArgumentNullException("Key");
// Declare the string used to hold
// the decrypted text.
string plaintext = null;
// Create an Aes object
// with the specified key and IV.
using (Aes aesAlg = Aes.Create()) {
aesAlg.Key = Key;
aesAlg.IV = IV;
// Create a decrytor to perform the stream transform.
ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);
// 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)) {
plaintext = srDecrypt.ReadToEnd();
}
}
}
}
return plaintext;
}
static byte[] GetBytes(string str) {
byte[] bytes = new byte[str.Length * sizeof(char)];
System.Buffer.BlockCopy(str.ToCharArray(), 0, bytes, 0, bytes.Length);
return bytes;
}
If you don't specify an IV, then one is randomly generated. You are using 2 different IV values when decrypting, which is why you are seeing different results.
I am trying to decode an AES cipher in C#. If I use the same AES object as when I encode them, everything is fine. But as soon as I create a different instance of AES, it does not work:
string original = "username,password,companyID";
byte[] encrypted;
using (Aes myAes1 = Aes.Create()) {
encrypted = EncryptStringToBytes_Aes(original, GetBytes("password"), myAes1.IV);
//test1
string test1 = DecryptStringFromBytes_Aes(encrypted, GetBytes("password"), myAes1.IV);
}
using (Aes myAes2 = Aes.Create()) {
//test2
string test2 = DecryptStringFromBytes_Aes(encrypted, GetBytes("password"), myAes2.IV);
}
So in this code, test1 uses myAes1 and it works out fine because the encryption also used myAes1. However test2 uses myAes2 and it doesn't work, here is the output:
test1 = username,password,companyID
test2 = t0�V�e]��Ԅ��yd,companyID
what am I doing wrong?
Here are the supporting functions, which I copied from online:
static byte[] EncryptStringToBytes_Aes(string plainText, byte[] Key,byte[] IV) {
// Check arguments.
if (plainText == null || plainText.Length <= 0)
throw new ArgumentNullException("plainText");
if (Key == null || Key.Length <= 0)
throw new ArgumentNullException("Key");
if (IV == null || IV.Length <= 0)
throw new ArgumentNullException("Key");
byte[] encrypted;
// Create an Aes object
// with the specified key and IV.
using (Aes aesAlg = Aes.Create()) {
aesAlg.Key = Key;
aesAlg.IV = IV;
// Create a decrytor to perform the stream transform.
ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);
// 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 encrypted;
}
static string DecryptStringFromBytes_Aes(byte[] cipherText, byte[] Key, byte[] IV) {
// Check arguments.
if (cipherText == null || cipherText.Length <= 0)
throw new ArgumentNullException("cipherText");
if (Key == null || Key.Length <= 0)
throw new ArgumentNullException("Key");
if (IV == null || IV.Length <= 0)
throw new ArgumentNullException("Key");
// Declare the string used to hold
// the decrypted text.
string plaintext = null;
// Create an Aes object
// with the specified key and IV.
using (Aes aesAlg = Aes.Create()) {
aesAlg.Key = Key;
aesAlg.IV = IV;
// Create a decrytor to perform the stream transform.
ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);
// 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)) {
plaintext = srDecrypt.ReadToEnd();
}
}
}
}
return plaintext;
}
static byte[] GetBytes(string str) {
byte[] bytes = new byte[str.Length * sizeof(char)];
System.Buffer.BlockCopy(str.ToCharArray(), 0, bytes, 0, bytes.Length);
return bytes;
}
If you don't specify an IV, then one is randomly generated. You are using 2 different IV values when decrypting, which is why you are seeing different results.
I have taken the decrypt code from http://msdn.microsoft.com/en-us/library/system.security.cryptography.cryptostream.aspx and modified it as follows below. I have an encrypted example, and it works just fine while decoding. But when using the encryption function, it returns junk string with strange symbols. below are the functions of encrypt/decrypt.
An example of encrypted string "hey" : "???U?b???z?Y???"
When decoded again: "ûc{ÁpÅ`ñ""Â"
I'm using this code to convert the byte array to string:
private string ByteArrayToString(byte[] input)
{
ASCIIEncoding dec = new ASCIIEncoding();
return dec.GetString(input);
}
here are the encrypt/decrypt functions. the decryption function is working fine.
private string DecryptStringFromBytesAes(byte[] cipherText, byte[] Key, byte[] IV)
{
// Check arguments.
if (cipherText == null || cipherText.Length <= 0)
throw new ArgumentNullException("cipherText");
if (Key == null || Key.Length <= 0)
throw new ArgumentNullException("Key");
// Declare the string used to hold
// the decrypted text.
string plaintext = null;
// Create an RijndaelManaged object
// with the specified key and IV.
using (RijndaelManaged aesAlg = new RijndaelManaged())
{
aesAlg.Key = Key;
aesAlg.Padding = PaddingMode.Zeros;
aesAlg.Mode = CipherMode.ECB;
// Create a decrytor to perform the stream transform.
ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);
// 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;
}
private byte[] EncryptStringToBytesAes(string plainText, byte[] Key, byte[] IV)
{
// Check arguments.
if (plainText == null || plainText.Length <= 0)
throw new ArgumentNullException("plainText");
if (Key == null || Key.Length <= 0)
throw new ArgumentNullException("Key");
byte[] encrypted;
// Create an RijndaelManaged object
// with the specified key and IV.
using (RijndaelManaged aesAlg = new RijndaelManaged())
{
aesAlg.Key = Key;
aesAlg.Padding = PaddingMode.Zeros;
aesAlg.Mode = CipherMode.ECB;
// Create a decrytor to perform the stream transform.
ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);
// 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 encrypted;
}
What you observe is the problem of mapping arbitrary bytes (in the range 0-255) to characters. Meaningful characters are only in the range 32-255 or even only 32-127 (ASCII). Values below 32 are the so-called non-printable characters and values above 127 are dependent on the character encoding you are using. That's why the crypted text looks like junk. Mast crypto-systems therefore transform the bytes into the sensible ASCII-range. One such algorithm is BASE64. So mangling the crypted bytes through BASE64 gives characters that are all printable and that will go without problems through e-mail. Before decrypting you then have to undo the BASE64 encoding.
Another way to make the encrypted result look better is to show the hexa-decimal representation of it. For example if you have a byte value of 15 you print 0F. You may use this to represent your byte array in hex:
private string ByteArrayToHexString(byte[] data)
{
return String.Concat(data.Select(b => b.ToString("x2")));
}
In order to have your output as a hexadecimal encoding of the data, follow the methods found here. I modified them slightly to be extension methods:
public static string ToHexString(this byte[] bytes)
{
return bytes == null ? string.Empty : BitConverter.ToString(bytes).Replace("-", string.Empty);
}
public static byte[] FromHexString(this string hexString)
{
if (hexString == null)
{
return new byte[0];
}
var numberChars = hexString.Length;
var bytes = new byte[numberChars / 2];
for (var i = 0; i < numberChars; i += 2)
{
bytes[i / 2] = Convert.ToByte(hexString.Substring(i, 2), 16);
}
return bytes;
}
Encrypted strings will look like garble. The way to test if the encryption is working correctly is to pass your string back through decrypt. If it works at decrypting then you know the string is correct despite looking like garbage to you.
I use the function EncryptStringToBytes to encrypt plain text to array of bytes and
finally convert array of bytes to string and return it then.
I use another function to Decrypt Encrypted text to plaint text.
I try to scramble a text with RC2 but it raises this error:
Rijndael class to encrypt and then decrypt data
Here's the code:
using System;
using System.IO;
using System.Text;
using System.Security.Cryptography;
namespace RC2CryptoServiceProvider_Examples
{
class MyMainClass
{
static string EncryptStringToBytes(string plainText, byte[] Key, byte[] IV)
{
// Check arguments.
if (plainText == null || plainText.Length <= 0)
throw new ArgumentNullException("plainText");
if (Key == null || Key.Length <= 0)
throw new ArgumentNullException("Key");
if (IV == null || IV.Length <= 0)
throw new ArgumentNullException("Key");
byte[] encrypted;
// Create an Rijndael object
// with the specified key and IV.
using (Rijndael rijAlg = Rijndael.Create())
{
rijAlg.Key = Key;
rijAlg.IV = IV;
// Create a decrytor to perform the stream transform.
ICryptoTransform encryptor = rijAlg.CreateEncryptor(rijAlg.Key, rijAlg.IV);
// 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 System.Text.Encoding.UTF8.GetString(encrypted);**
}
static string DecryptStringFromBytes(string Codedtext, byte[] Key, byte[] IV)
{
byte[] cipherText = System.Text.Encoding.UTF8.GetBytes(Codedtext);
// Check arguments.
if (cipherText == null || cipherText.Length <= 0)
throw new ArgumentNullException("cipherText");
if (Key == null || Key.Length <= 0)
throw new ArgumentNullException("Key");
if (IV == null || IV.Length <= 0)
throw new ArgumentNullException("Key");
// Declare the string used to hold
// the decrypted text.
string plaintext = null;
// Create an Rijndael object
// with the specified key and IV.
using (Rijndael rijAlg = Rijndael.Create())
{
rijAlg.Key = Key;
rijAlg.IV = IV;
// Create a decrytor to perform the stream transform.
ICryptoTransform decryptor = rijAlg.CreateDecryptor(rijAlg.Key, rijAlg.IV);
// 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;
}
public static void Main()
{
try
{
System.Text.UTF8Encoding enc = new System.Text.UTF8Encoding();
string original = "Here is some data to encrypt!";
// Create a new instance of the Rijndael
// class. This generates a new key and initialization
// vector (IV).
using (Rijndael myRijndael = Rijndael.Create())
{
// Encrypt the string to an array of bytes.
string encrypted = EncryptStringToBytes(original, myRijndael.Key, myRijndael.IV);
// Decrypt the bytes to a string.
string roundtrip = DecryptStringFromBytes(encrypted, myRijndael.Key, myRijndael.IV);
//Display the original data and the decrypted data.
Console.WriteLine("Original: {0}", original);
Console.WriteLine("Round Trip: {0}", roundtrip);
}
}
catch (Exception e)
{
Console.WriteLine("Error: {0}", e.Message);
}
Console.ReadLine();
}
}
}
This is the problem (or at least a problem):
return System.Text.Encoding.UTF8.GetString(encrypted);
The encrypted data isn't UTF-8 text. It's arbitrary binary data. Don't treat it as if it were encoded text.
If you really need to pass arbitrary binary data around as a string, use Base64:
return Convert.ToBase64String(encrypted);
Then in DecryptStringFromBytes, you'd use:
byte[] cipherText = Convert.FromBase64String(codedText);
(Parameter name changed to comply with conventions.)