Re: Can't get basic encryption to work

This is basically fine. Sometimes it is a good idea to be more explicit
about the encoding method that is used to convert the string to binary in
the stream, as this can cause headaches. In your case, you are probably
fine since you are wrapping with StreamWriter/StreamReader and that uses
UTF8 by default on both ends.

Also, if you convert the encrypted data to string, make sure you use Base64.

Another thing to be aware of is proper usage of IV. It is supposed to be
random and should be different each time. It is not a secret though like
the key. As such, you generally want to generate a new IV with each
encryption and store the IV you used with the encrypted data so that you can
recover the IV that was used when you go to decrypt. One way that people
often do this is to generate new random IV and append it to the beginning of
the array of encrypted data. If you know how long it is (which you should),
then you just pull off the first X bytes as IV before doing the encryption.

Using a static IV, an "all 0" IV or an IV that is the same as the key all
undermine what the IV is used for (which is to help ensure that the same
input will produce different encrypted output each time and will thus make
your data harder to plaintext attack).

Joe K.

--
Joe Kaplan-MS MVP Directory Services Programming
Co-author of "The .NET Developer's Guide to Directory Services Programming"
http://www.directoryprogramming.net
--
"DXRick" <DXRick@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:D506FB89-4530-49A7-AB96-9CD3F2F4CE26@xxxxxxxxxxxxxxxx
Thanks both of you. I was doing that BEFORE the write command, and was
then
getting a padding error exception in the decryption routine. Now, the
encryption and decryption both work.

So, here is my final code (the stuff above it is the same):

mStream = new MemoryStream();
cStream = new CryptoStream(mStream, encryptor, CryptoStreamMode.Write);
sWriter = new StreamWriter(cStream);
sWriter.Flush();
sWriter.Write(dataToEncrypt);
sWriter.Flush();
cStream.FlushFinalBlock();

this.encryptedData = mStream.ToArray();



Thanks!


"Joe Kaplan" wrote:

You should always call FlushFinalBlock when working with block ciphers
(which AES/Rjindael is one of). Block ciphers need to add padding to
data
to make the final output be an even block size, so they need to know when
you are done adding data.

Joe K.

--
Joe Kaplan-MS MVP Directory Services Programming
Co-author of "The .NET Developer's Guide to Directory Services
Programming"
http://www.directoryprogramming.net
--
"DXRick" <DXRick@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:10F02053-2B27-4D99-A518-5AC9C4355861@xxxxxxxxxxxxxxxx
Where did you add those? If I try to close the writer before the
sWriter.Write() command I get an exception that it cannot write to a
closed
stream.

If I just include this command, I will get a 16 byte array in hookie:

cStream.FlushFinalBlock();

I have no clue why that would be needed.

Thanks.

"Dominick Baier" wrote:

adding an

sWriter.Flush();
sWriter.Close();

works for me...


-----
Dominick Baier (http://www.leastprivilege.com)

Developing More Secure Microsoft ASP.NET 2.0 Applications
(http://www.microsoft.com/mspress/books/9989.asp)

Those did not work.

This:

int sttr = (int)mStream.Length;

give me a 0 length. The MemoryStream is not being used?

Thanks.

"Dominick Baier" wrote:

just some ideas:

try to flush the streamwriter first...
if that doesn't help, try to position the memstream to the
beginning
(using
..Seek)
-----
Dominick Baier (http://www.leastprivilege.com)
Developing More Secure Microsoft ASP.NET 2.0 Applications
(http://www.microsoft.com/mspress/books/9989.asp)

I am just trying to encrypt some data and am pretty much copying
the
code that the MSDN docs have for the RijndaelManaged class:

RijndaelManaged cryptAlg = null;
MemoryStream mStream = null;
CryptoStream cStream = null;
StreamWriter sWriter = null;
try
{
cryptAlg = new RijndaelManaged();
ICryptoTransform encryptor =
cryptAlg.CreateEncryptor(cryptAlg.Key,
cryptAlg.IV);
mStream = new MemoryStream();
cStream = new CryptoStream(mStream, encryptor,
CryptoStreamMode.Write);
sWriter = new StreamWriter(cStream);
sWriter.Write(dataToEncrypt); // encrypt a string
byte[] hookie = mStream.ToArray(); ***GETTING NOTHING HERE***
}
The MemoryStream mStream has nothing in it after this. The Length
is
0 and I get no data from it. Since I just copied the code from
the
MSDN example, I can't figure out what is wrong. I am just doing
this
in a console app right now. So nothing fancy here.
Please help!

Thanks!









.

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