Cryptography

[dscanlan]

I'm trying to encrypt and decrypt a file using RijndaelManaged().

I've created a key and a vector which is stored in a file key.txt. I've encrypted a file using:

StreamReader re = new StreamReader(sKeyFile);
string s = re.ReadToEnd();
int iKeyEndPoint;
iKeyEndPoint = s.IndexOf("KEY");

string sKey = s.Substring(0, (iKeyEndPoint));
string sIV = s.Remove(0, iKeyEndPoint);
sIV = sIV.Replace("KEY", "");

//convert strings to byte arrays
ASCIIEncoding encoding = new ASCIIEncoding();
byte[] aKey = encoding.GetBytes(sKey);
byte[] aIV = encoding.GetBytes(sIV);


// open file to encrypt
FileStream fsInput = new FileStream(sInputFilename, FileMode.Open, FileAccess.Read);

byte[] encryptedData;
byte[] aData = new byte[fsInput.Length];
fsInput.Read(aData, 0, aData.Length);

RijndaelManaged rijndael = new RijndaelManaged();
//rijndael.Padding = PaddingMode.None;
rijndael.Padding = PaddingMode.ANSIX923;
ICryptoTransform encryptor = rijndael.CreateEncryptor(aKey, aIV);

using (MemoryStream memoryStream = new MemoryStream())
{
using (CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
{
cryptoStream.Write(aData, 0, aData.Length);
cryptoStream.FlushFinalBlock();
}

encryptedData = memoryStream.ToArray();
}

//convert from byte array to string
String sData = System.Text.ASCIIEncoding.ASCII.GetString(encryptedData);

FileStream fsEncypt = new FileStream(sEncryptedFile, FileMode.OpenOrCreate, FileAccess.Write);

// Create a StreamWriter using the CryptoStream.
StreamWriter sWriter = new StreamWriter(fsEncypt);

try
{
//write the encrypted string
sWriter.WriteLine(sData);
}

This seems to work fine (at least a get some text in the sEncryptedFile file).

when i try to decrypt it i get a "Length of the data to decrypt is invalid." error. Code is as follows:

RijndaelManaged rijndael = new RijndaelManaged();
rijndael.Padding = PaddingMode.ANSIX923;


//Get the Key and Vector from File
StreamReader re = new StreamReader("C:\\key.txt");

string s = re.ReadToEnd();
int iKeyEndPoint;
iKeyEndPoint = s.IndexOf("KEY");

string sKey = s.Substring(0, (iKeyEndPoint));
string sIV = s.Remove(0, iKeyEndPoint);
sIV = sIV.Replace("KEY", "");

//convert strings to byte arrays
ASCIIEncoding encoding = new ASCIIEncoding();
byte[] aKey = encoding.GetBytes(sKey);
byte[] aIV = encoding.GetBytes(sIV);

ICryptoTransform decryptor = rijndael.CreateDecryptor(aKey, aIV);

FileStream fEncryptStream = new FileStream("C:\\Encrypted.txt", FileMode.Open, FileAccess.Read);

byte[] aData = new byte[fEncryptStream.Length];
fEncryptStream.Read(aData, 0, aData.Length);

string str = System.Text.ASCIIEncoding.ASCII.GetString(aData);

byte[] decrypted;
using (MemoryStream memoryStream = new MemoryStream(aData))
{
using (CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
{
int length = aData.Length;
decrypted = new byte[length];

cryptoStream.Read(decrypted, 0, length);
}
}

str = System.Text.ASCIIEncoding.ASCII.GetString(decrypted);


I've tried adding rijndael.Padding = none and removing this live all together. If anyone can point out anything that i've done wrong that would help a great deal!