I was wondering why the first 16 bytes of all my strings being encrypted, then when being decrypted are missing and how to fix this if it is possible. I am encrypting like so in c#
public static string EncryptString(string b_key, string plainText)
{
byte[] iv = new byte[16];
byte[] array;
using (Aes aes = Aes.Create())
{
aes.Key = Convert.FromBase64String(b_key);
aes.IV = iv;
ICryptoTransform encryptor = aes.CreateEncryptor(aes.Key, aes.IV);
using (MemoryStream memoryStream = new MemoryStream())
{
using (CryptoStream cryptoStream = new CryptoStream((Stream)memoryStream, encryptor, CryptoStreamMode.Write))
{
using (StreamWriter streamWriter = new StreamWriter((Stream)cryptoStream))
{
streamWriter.Write(plainText);
}
array = memoryStream.ToArray();
}
}
}
return Convert.ToBase64String(array);
}
and decrypting in python3 like so
enc = base64.b64decode(self.text)
iv = enc[:16]
cipher = AES.new(self.key, AES.MODE_CBC, iv)
plain_text = cipher.decrypt(enc[16:])
plain_text = self.dePKCS7_padding(plain_text)
return plain_text
Is readding the first 16 bytes possible? or must be used for encryption. I also want it to crypto safe but the first 16 bytes are kind of important is this possible? anyway to get around this in either c# or python3?
Based on the discussion in comments and inputs from #MichaelFehr and #user9014097, I came up with the following code.
In this code the IV of AES will have random value created when AES.Create() is called. And the same will be used in the outcome of the encrypted value.
The decryptString method will capture the iv value from the incoming encrypted string and assign it to AES while decrypting the string.
public static string EncryptString(string b_key, string plainText)
{
byte[] array;
using (Aes aes = Aes.Create())
{
aes.Key = Convert.FromBase64String(b_key);
ICryptoTransform encryptor = aes.CreateEncryptor(aes.Key, aes.IV);
using (MemoryStream memoryStream = new MemoryStream())
{
// Adding aes.IV to the stream's start.
memoryStream.Write(aes.IV);
using (CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
{
using (StreamWriter streamWriter = new StreamWriter(cryptoStream))
{
streamWriter.Write(plainText);
}
}
array = memoryStream.ToArray();
}
}
// The final encrypted outcome will be aes.IV+encryptedtext.
return Convert.ToBase64String(array);
}
public static string DecryptString(string key, string cipherText)
{
//input is iv+encrypted text, convert them to byte array.
byte[] buffer = Convert.FromBase64String(cipherText);
// byte array for iv
byte[] iv = new byte[16];
// byte array for rest of the cipher text.
byte[] cipherBuffer = new byte[buffer.Length - 16];
// copy first 16 bytes from the cipher text to iv.
Buffer.BlockCopy(buffer, 0, iv, 0, 16);
// copy rest of the cipher text to the cipher buffer to be decrypted.
Buffer.BlockCopy(buffer, 16, cipherBuffer, 0, buffer.Length - 16);
using (Aes aes = Aes.Create())
{
aes.Key = Convert.FromBase64String(key);
aes.IV = iv;
ICryptoTransform decryptor = aes.CreateDecryptor(aes.Key, aes.IV);
using (MemoryStream memoryStream = new MemoryStream(cipherBuffer))
{
using (CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
{
using (StreamReader streamReader = new StreamReader(cryptoStream))
{
return streamReader.ReadToEnd();
}
}
}
}
}
I have following assumption in writing above code.
Length of IV is 16.
Python code (shared above) does not need split the input text based on some specific character. It takes first 16 bytes as IV value and rest of the bytes as cipher text.
I was able to encrypt and decrypt values successfully in C# using above methods.
I was not able to decrypt the value in python code as I have little to no idea on how to work with python.
You can test the outcome of above encryption in python to decrypt it. Let me know if it doesn't work as expected.
I hope this will help you solve your issue.
Related
I am quite new to AES Encryption and therefore have some question about IV and Key
The code I have written works, i can both encrypt and decrypt a String
Just for fun i tried to go on a Website https://www.devglan.com/online-tools/aes-encryption-decryption
And tried to see if the website can decrypt, if i give the same key and IV. but I ran into an error
The website said "Length of secret key should be 32 for 256 bits key size"
and "Length of initialization vector must be 16 with AES."
Is there anything I have done wrong?
static void Main(string[] args)
{
byte[] key = GenerateRandomByteArray(32);
Console.WriteLine($"Key: {Convert.ToBase64String(key)}");
byte[] encrypted = EncryptMessage("test message", key);
Console.WriteLine($"Encrypted : {Convert.ToBase64String(encrypted)}");
string decrypted = DecryptMessage(encrypted, key);
Console.WriteLine($"Decrypted: {decrypted}");
Console.ReadLine();
}
private static byte[] GenerateRandomByteArray(int size)
{
using (RandomNumberGenerator rng = RandomNumberGenerator.Create())
{
byte[] buffer = new byte[size];
rng.GetBytes(buffer);
return buffer;
}
}
public static byte[] EncryptMessage(string mess, byte[] secretkey)
{
byte[] encrypted;
using (Aes aes = Aes.Create())
{
aes.Key = secretkey;
//Generates a IV with 16 random bytes
aes.IV = GenerateRandomByteArray(16);
Console.WriteLine($"IV: {Convert.ToBase64String(aes.IV)}");
// Create an encryptor to perform the stream transform.
ICryptoTransform encryptor = aes.CreateEncryptor(aes.Key, aes.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))
{
//Writes the IV, so when we decrypt we can get the first 16 bytes where IV i located
msEncrypt.Write(aes.IV, 0, aes.IV.Length);
//Write all data to the stream.
swEncrypt.Write(mess);
}
encrypted = msEncrypt.ToArray();
}
}
}
// Return the encrypted bytes from the memory stream.
return encrypted;
}
public static string DecryptMessage(byte[] mess, byte[] key)
{
string plaintext = null;
// Create an Aes object
using (Aes aes = Aes.Create())
{
//Sets the AES key
aes.Key = key;
using (MemoryStream msDecrypt = new MemoryStream(mess))
{
//Reads the first 16 bytes from the message which is where the IV i stored
byte[] iv = new byte[aes.BlockSize / 8];
msDecrypt.Read(iv, 0, iv.Length);
//Sets the IV
aes.IV = iv;
// Create a decryptor to perform the stream transform.
ICryptoTransform decryptor = aes.CreateDecryptor(aes.Key, aes.IV);
// Create the streams used for decryption.
//using (MemoryStream msDecrypt = new MemoryStream(mess))
//{
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;
}
Is i remember right GenerateRandomByteArray(32) is 256 bits for Key
And GenerateRandomByteArray(16) is 128 bits for IV
Output from Console:
Key: 3dmQoxqrAyoc5kMKQIQl8Hp4UVVCE8B64S19iNZOQRY=
IV: kO1nKUs08c/8mrlbHj3/xQ==
Encrypted : kO1nKUs08c/8mrlbHj3/xR43S5L3BJ5Ueg01xngw93I=
Decrypted: test message
I have been trying to implement proper IV practice in methods to encrypt and decrypt a UTF-8 string with AES which is then returned as a Base64 string. Using this question as a reference, I have prepended the generated IV to the byte array before the Base64 conversion. I'm having an issue where the decrypt method returns the UTF-8 string with exactly fifty characters of random junk (encryption artifacts?). I don't believe the issue is with the encryption because the decrypt method does consistently return the encrypted string. I think the problem is with one of the other conversion steps but I'm having trouble seeing where this might be coming from. Any help would be wildly appreciated.
Encrypt method
public static string EncryptString(string input, string key)
{
using (var aes = new AesCryptoServiceProvider())
{
aes.Key = System.Convert.FromBase64String(key);
aes.Mode = CipherMode.CBC;
aes.Padding = PaddingMode.PKCS7;
byte[] rawData = Encoding.UTF8.GetBytes(input);
// IV is the 16 byte AES Initialization Vector
aes.GenerateIV();
using (var encryptor = aes.CreateEncryptor(aes.Key, aes.IV))
{
using (var ms = new MemoryStream())
{
ms.Write(aes.IV, 0, aes.IV.Length); // aes.IV.Length should be 16
using (var cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
{
cs.Write(rawData, 0, rawData.Length);
cs.FlushFinalBlock();
}
byte[] encryptedData = ms.ToArray();
// this will hold the IV prepended to the encrypted data
byte[] output = new byte[aes.IV.Length + encryptedData.Length];
Array.Copy(aes.IV, output, aes.IV.Length); // save the iv
Array.Copy(encryptedData, 0, output, aes.IV.Length, encryptedData.Length); // save the data
// now encode the whole thing as base 64
return System.Convert.ToBase64String(output);
}
}
}
}
Decrypt method
public static string DecryptString(string input, string key)
{
using (var aes = new AesCryptoServiceProvider())
{
aes.Key = Convert.FromBase64String(key);
aes.Mode = CipherMode.CBC;
aes.Padding = PaddingMode.PKCS7;
byte[] rawData = Convert.FromBase64String(input);
byte[] IV = new byte[16]; // aes.IV.Length should be 16
Array.Copy(rawData, IV, IV.Length);
using (var ms = new MemoryStream())
{
using (var cs = new CryptoStream(ms, aes.CreateDecryptor(aes.Key, IV), CryptoStreamMode.Write))
{
using (var binaryWriter = new BinaryWriter(cs))
{
binaryWriter.Write(rawData,IV.Length ,rawData.Length - IV.Length);
}
}
return Encoding.UTF8.GetString(ms.ToArray());
}
}
}
My test
static void Main(string[] args)
{
string payload = "My super secret string";
string key = "tR4mPn7mBQ8G6HWusyFnGk/gqdd/enWiUTr7YbhNrJg=";
Console.WriteLine(payload);
Console.WriteLine(key);
Console.WriteLine("");
string encrypted = EncryptString(payload, key);
Console.WriteLine(encrypted);
Console.WriteLine("");
string decrypted = DecryptString(encrypted, key);
Console.WriteLine(decrypted);
Console.WriteLine(decrypted.Length.ToString() + " " + encrypted.Length.ToString());
Console.ReadKey();
}
Edit to add - this is an example of the output:
�XQ��=F�]�D�?�My super secret string
You are writing the IV to the output twice in EncryptString. First you have:
ms.Write(aes.IV, 0, aes.IV.Length); // aes.IV.Length should be 16
which is the start of encryptedData. You then copy the IV and encryptedData (which already includes the IV) into a new byte array:
// this will hold the IV prepended to the encrypted data
byte[] output = new byte[aes.IV.Length + encryptedData.Length];
Array.Copy(aes.IV, output, aes.IV.Length); // save the iv
Array.Copy(encryptedData, 0, output, aes.IV.Length, encryptedData.Length); // save the data
This doubling of the IV is what is causing the extra bytes.
You don’t need to do the second copying. Just convert encryptedData to base 64 directly and return that:
return System.Convert.ToBase64String(encryptedData);
when i use this code to encrypt and decrypt i got an error said
Padding is invalid and cannot be removed.
any idea
public static class Crypto
{
private static readonly byte[] initVectorBytes = Encoding.ASCII.GetBytes("tu89geji340t89u2");
// This constant is used to determine the keysize of the encryption algorithm.
private const int keysize = 256;
public static string Encrypt(string plainText, string passPhrase)
{
byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);
using (PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null))
{
byte[] keyBytes = password.GetBytes(keysize / 8);
using (RijndaelManaged symmetricKey = new RijndaelManaged())
{
symmetricKey.Mode = CipherMode.CBC;
using (ICryptoTransform encryptor = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes))
{
using (MemoryStream memoryStream = new MemoryStream())
{
using (CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
{
cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
cryptoStream.FlushFinalBlock();
byte[] cipherTextBytes = memoryStream.ToArray();
return Convert.ToBase64String(cipherTextBytes);
}
}
}
}
}
}
public static string Decrypt(string cipherText, string passPhrase)
{
byte[] cipherTextBytes = Convert.FromBase64String(cipherText);
using (PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null))
{
byte[] keyBytes = password.GetBytes(keysize / 8);
using (RijndaelManaged symmetricKey = new RijndaelManaged())
{
symmetricKey.Mode = CipherMode.CBC;
using (ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes))
{
using (MemoryStream memoryStream = new MemoryStream(cipherTextBytes))
{
using (CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
{
byte[] plainTextBytes = new byte[cipherTextBytes.Length];
int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);
}
}
}
}
}
}
}
I tried the following using your methods and it worked fine:
var passPhrase = "123456";
var e = Encrypt("testtesttesttest", passPhrase);
Console.WriteLine(e); // YEtSJshcn686ZO+JlEQ48ap/odhuvIGalbAT1XhinqQ=
var d = Decrypt(e, passPhrase);
Console.WriteLine(d); // testtesttesttest
This suggests that you're either passing a different passPhrase to Decrypt() to the one you passed to Encrypt(), or that you are somehow corrupting the ciphertext prior to decryption. (Are you perhaps calling Decrypt with the ciphertext and passphrase parameters reversed?)
It's also worth noting that essentially everything in the comments at the top of your code is wrong:
You're not passing any salt to PasswordDeriveBytes.
The size of the IV must be equal to the block size (16 bytes), it is unrelated to the key size used.
Passing a 16 character string through Encoding.ASCII.GetBytes() results in a 16 byte output, not 32 bytes. (This rather coincidentally means that your initVectorBytes is in fact the correct length for the IV).
Furthermore, PasswordDeriveBytes is deprecated and should not be used. You should be using Rfc2898DeriveBytes instead, and you should be using a proper salt value. The IV should also not be a static value, and definitely not one derived from an ASCII string!
I'm trying to read a file, encrypt it, and send it to a server over socket, where it is written. And then the other way around, read it on server, send it to client, decrypt it, and write it again.
My problem using C# Aes class is, that the input size doesn't equal the output size.
For example, when I read 4096 bytes from the file, the output size is 4112 bytes, 16 bytes more. OK, so 4112 bytes are sent and written on the server, but when I get the file again, I can only send a maximum of 4096 bytes over the socket, and then, of course, the decrypt function on client throws an exception, that the padding is invalid and cannot be removed. Sure I could try to read less bytes on the client, but that doesn't work as well.
I'm a very experienced C++ programmer, and I've done this with OpenSsl, and it worked like a charm. The input size has been always the output size, I don't know what is wrong with my functions in C#.
this is the sending part:
byte[] SendData = new byte[4096];
iBytesRead = FileRead.Read (SendData, 0, 4096);
SendData = aes.encrypt (Encoding.Default.GetString (SendData, 0, iBytesRead), iBytesRead);
String a = aes.decrypt (SendData); // no problems here because the size is correct
Socket.sendB (SendData, SendData.Length);
and the part of receiving from server:
byte[] WriteData = new byte[4096],
Temp;
if ((iBytesReceived = Socket.receiveB (ref WriteData)) == 0)
break;
if (Encoding.ASCII.GetString (WriteData, 0, iBytesReceived) == "end")
break;
for (uint i = 0; i < iBytesReceived; i++)
Temp[i] = WriteData[i];
byte[] a = Encoding.Default.GetBytes (aes.decrypt (Temp));
FileWrite.Write (a, 0, Temp.Length);
Aes functions:
public byte[] encrypt(String _InStr, int _InStrLength)
{
if (!bKeySet)
return ErrorReturn;
byte[] encrypted;
using (Aes aes = Aes.Create ())
{
aes.Key = Key;
aes.IV = IV;
//aes.Padding = PaddingMode.PKCS7;
//aes.BlockSize = 128;
//aes.KeySize = 128;
//aes.Mode = CipherMode.CFB;
ICryptoTransform encryptor = aes.CreateEncryptor(aes.Key, aes.IV);
// Create the streams used for encryption.
using (MemoryStream ms = new MemoryStream())
{
using (CryptoStream cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
{
using (StreamWriter sw = new StreamWriter(cs))
{
sw.Write(_InStr);
}
}
ms.Close ();
encrypted = ms.ToArray ();
}
}
return encrypted;
}
public String decrypt(byte[] _InStr)
{
if (!bKeySet)
return "";
String plaintext;
using (Aes aes = Aes.Create ())
{
aes.Key = Key;
aes.IV = IV;
//aes.Padding = PaddingMode.PKCS7;
//aes.BlockSize = 128;
//aes.KeySize = 128;
//aes.Mode = CipherMode.CBC;
ICryptoTransform decryptor = aes.CreateDecryptor(aes.Key, aes.IV);
// Create the streams used for decryption.
using (MemoryStream msDecrypt = new MemoryStream(_InStr))
{
using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
{
using (StreamReader srDecrypt = new StreamReader(csDecrypt))
{
plaintext = srDecrypt.ReadToEnd ();
}
}
}
}
return plaintext;
}
As it was said, if any padding is used, the output will be aligned to a block size. However .Net doesn't want to work with incomplete blocks when PaddingMode.None is used. You should pad data yourself before encryption(decryption) and remove added bytes after.
One of the way to do this is to wrap ICryptoTransform passed to a CryptoStream
I'm trying to get simple encryption/decryption working with AesManaged, but I keep getting an exception when trying to close the decryption stream. The string here gets encrypted and decrypted correctly, and then I get the CryptographicException "Padding was invalid and cannot be removed" after Console.WriteLine prints the correct string.
Any ideas?
MemoryStream ms = new MemoryStream();
byte[] rawPlaintext = Encoding.Unicode.GetBytes("This is annoying!");
using (Aes aes = new AesManaged())
{
aes.Padding = PaddingMode.PKCS7;
aes.Key = new byte[128/8];
aes.IV = new byte[128/8];
using (CryptoStream cs = new CryptoStream(ms, aes.CreateEncryptor(),
CryptoStreamMode.Write))
{
cs.Write(rawPlaintext, 0, rawPlaintext.Length);
cs.FlushFinalBlock();
}
ms = new MemoryStream(ms.GetBuffer());
using (CryptoStream cs = new CryptoStream(ms, aes.CreateDecryptor(),
CryptoStreamMode.Read))
{
byte[] rawData = new byte[rawPlaintext.Length];
int len = cs.Read(rawData, 0, rawPlaintext.Length);
string s = Encoding.Unicode.GetString(rawData);
Console.WriteLine(s);
}
}
The trick is to use MemoryStream.ToArray().
I also changed your code so that it uses the CryptoStream to Write, in both encrypting and decrypting. And you don't need to call CryptoStream.FlushFinalBlock() explicitly, because you have it in a using() statement, and that flush will happen on Dispose(). The following works for me.
byte[] rawPlaintext = System.Text.Encoding.Unicode.GetBytes("This is all clear now!");
using (Aes aes = new AesManaged())
{
aes.Padding = PaddingMode.PKCS7;
aes.KeySize = 128; // in bits
aes.Key = new byte[128/8]; // 16 bytes for 128 bit encryption
aes.IV = new byte[128/8]; // AES needs a 16-byte IV
// Should set Key and IV here. Good approach: derive them from
// a password via Cryptography.Rfc2898DeriveBytes
byte[] cipherText= null;
byte[] plainText= null;
using (MemoryStream ms = new MemoryStream())
{
using (CryptoStream cs = new CryptoStream(ms, aes.CreateEncryptor(), CryptoStreamMode.Write))
{
cs.Write(rawPlaintext, 0, rawPlaintext.Length);
}
cipherText= ms.ToArray();
}
using (MemoryStream ms = new MemoryStream())
{
using (CryptoStream cs = new CryptoStream(ms, aes.CreateDecryptor(), CryptoStreamMode.Write))
{
cs.Write(cipherText, 0, cipherText.Length);
}
plainText = ms.ToArray();
}
string s = System.Text.Encoding.Unicode.GetString(plainText);
Console.WriteLine(s);
}
Also, I guess you know you will want to explicitly set the Mode of the AesManaged instance, and use System.Security.Cryptography.Rfc2898DeriveBytes to derive the Key and IV from a password and salt.
see also:
- AesManaged
This exception can be caused by a mismatch of any one of a number of encryption parameters.
I used the Security.Cryptography.Debug interface to trace all parameters used in the encrypt/decrypt methods.
Finally I found out that my problem was that I set the KeySize property after setting the Key causing the class to regenerate a random key and not using the key that I was initially set up.
For whats its worth, I'll document what I faced. I was trying to read the encryptor memory stream before the CryptoStream was closed. I was naive and I wasted a day debugging it.
public static byte[] Encrypt(byte[] buffer, byte[] sessionKey, out byte[] iv)
{
byte[] encrypted;
iv = null;
using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider { Mode = CipherMode.CBC, Padding = PaddingMode.PKCS7 })
{
aesAlg.Key = sessionKey;
iv = aesAlg.IV;
ICryptoTransform encryptor = aesAlg.CreateEncryptor(sessionKey, iv);
// Create the streams used for encryption.
using (MemoryStream msEncrypt = new MemoryStream())
{
using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
{
csEncrypt.Write(buffer, 0, buffer.Length);
//This was not closing the cryptostream and only worked if I called FlushFinalBlock()
//encrypted = msEncrypt.ToArray();
}
encrypted = msEncrypt.ToArray();
return encrypted;
}
}
}
Moving the encryptor memory stream read after the cypto stream was closed solved the problem. As Cheeso mentioned. You don't need to call the FlushFinalBlock() if you're using the using block.
byte[] rawData = new
byte[rawPlaintext.Length];
You need to read the length of the buffer, that probably includes the necessary padding (IIRC, been a few years).
Nobody answered, that actually MemoryStream.GetBuffer returns the allocated buffer, not the real data in this buffer. In this case it returns 256-byte buffer, while it contains only 32 bytes of encrypted data.
As others have mentioned, this error can occur if the key/iv is not correctly initialized for decryption. In my case I need to copy key and iv from some larger buffer. Here's what I did wrong:
Does not work: (Padding is invalid and cannot be removed)
aes.Key = new byte[keySize];
Buffer.BlockCopy(someBuffer, keyOffset, aes.Key, 0, keySize);
aes.IV = new byte[ivSize];
Buffer.BlockCopy(someBuffer, ivOffset, aes.IV, 0, ivSize);
Works:
var key = new byte[keySize];
Buffer.BlockCopy(someBuffer, keyOffset, key, 0, keySize);
aes.Key = key;
var iv = new byte[ivSize];
Buffer.BlockCopy(someBuffer, ivOffset, iv, 0, ivSize);
aes.IV = iv;
The OP did not make this mistake, but this might be helpful for others seeing the same error.