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POFile ecnryption using DES decrypting garbage - C#
 

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  1. POFile ecnryption using DES decrypting garbage - C#
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    <p>I am trying to write a simple file encrypter in C# using <code>DESCryptoServiceProvider</code>. The file format I am encrypting is <code>.jpg</code>. The encryption appears to look fine, but when I decrypt the encrypted file I get an error message in Windows Photo Viewer.</p> <p>Here is my code:</p> <pre><code>public static void Encrypt(string inputFileName, string outputFileName, string key) { var inputPath = path + "\\" + inputFileName; var outputPath = path + "\\" + outputFileName; try { FileStream fsInput = new FileStream(inputPath, FileMode.Open, FileAccess.Read); FileStream fsEncrypted = new FileStream(outputPath, FileMode.Create, FileAccess.Write); DESCryptoServiceProvider DES = new DESCryptoServiceProvider(); DES.Key = ASCIIEncoding.ASCII.GetBytes(key); DES.IV = ASCIIEncoding.ASCII.GetBytes(key); DES.Padding = PaddingMode.None; ICryptoTransform desencrypt = DES.CreateEncryptor(); CryptoStream cryptostream = new CryptoStream(fsEncrypted, desencrypt, CryptoStreamMode.Write); byte[] bytearrayinput = new byte[fsInput.Length - 1]; fsInput.Read(bytearrayinput, 0, bytearrayinput.Length); cryptostream.Write(bytearrayinput, 0, bytearrayinput.Length); Console.WriteLine("file encrypted @ {0}", outputFileName); } catch(Exception ex) { Console.WriteLine("catch in encryption: " + ex.Message + "\n\nclosing..."); } } public static void Decrypt(string inputFileName, string outputFileName, string key) { var inputPath = path + "\\" + inputFileName; var outputFileHoler = inputFileName.Substring(0, (outputFileName.IndexOf('.') + 4)); //FIX TO REMOVE REGEX var outputPath = path + "\\" + outputFileHoler; Console.WriteLine(outputPath); //TEMP try { DESCryptoServiceProvider DES = new DESCryptoServiceProvider(); DES.Key = ASCIIEncoding.ASCII.GetBytes(key); DES.IV = ASCIIEncoding.ASCII.GetBytes(key); DES.Padding = PaddingMode.None; FileStream fsread = new FileStream(inputPath, FileMode.Open, FileAccess.Read); ICryptoTransform desdecrypt = DES.CreateDecryptor(); CryptoStream cryptostream = new CryptoStream(fsread, desdecrypt, CryptoStreamMode.Read); StreamWriter fsDecrypted = new StreamWriter(outputPath); fsDecrypted.Write(new StreamReader(cryptostream).ReadToEnd()); fsDecrypted.Flush(); fsDecrypted.Close(); Console.WriteLine("file decrypted @ {0}", outputPath); } catch (Exception ex) { Console.WriteLine("catch in decryption: " + ex.Message + "\n\nclosing..."); } } </code></pre> <p>What am I doing wrong? </p> <p>PS. completely new to cryptography, please forgive me if it is something simple... </p>
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      1. POFile ecnryption using DES decrypting garbage - C#
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    1. CO1) You don't close the streams during encryption 2) You don't check the return value of `Read`. It may read less data than what you request. 3) padding=none will crash if the file length isn't a multiple of 8 bytes. Use PKCS7 instead. 4) Don't use `StreamReader`. It's designed for text, not binary data.
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    2. CO5) DES is very weak 6) Don't use an ASCII string as key 7) don't use a constant as IV 8) Add a MAC
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    3. COwhoa...thanks. I know (in theory) DES is weak...just doing this for my own edu really. Thanks for the info, will fix up what you mentioned.
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