Encrypt bitmap image for C# Windows application [modified]

[nudma]

Hi All!! In code below, i'm encrypting bitmap(24-bit) image, accessed from ms-access database. Here is my code:

private void button1_Click(object sender, System.EventArgs e)
{
string connString = "provider=Microsoft.Jet.OLEDB.4.0;" + @"data
source=D:\\practiceproject\practice.mdb";
OleDbConnection connection = new OleDbConnection(connString);
string commandString = "Select Image from readImage where ID=1";
OleDbCommand cmd = new OleDbCommand(commandString,connection);
byte[] toEncrypt = new byte[120154];
connection.Open();
toEncrypt = (Byte[]) cmd.ExecuteScalar();
connection.Close();

		RSAParameters rsaPubParams;
		RSAParameters rsaPrivateParams;
		RSACryptoServiceProvider rsaCSP = new RSACryptoServiceProvider();
        
		//Generate public and private key data.
		rsaPrivateParams = rsaCSP.ExportParameters(true);
		rsaPubParams = rsaCSP.ExportParameters(false);
		rsaCSP.ImportParameters(rsaPubParams);

		byte\[\] encrypted = new byte\[130000\];
		encrypted =  rsaCSP.Encrypt(toEncrypt, false);

		//MemoryStream ms = new MemoryStream();
		//ms.Write(encrypted, 78, encrypted.Length - 78);	
	}

But i get

Bad Length

error at line

encrypted = rsaCSP.Encrypt(toEncrypt, false);

Please help me to resolve this problem!!!

modified on Thursday, March 19, 2009 11:35 AM

[Michael Bookatz]

the way you've posted your code makes it very hard to read... please unbold and use a code block then people will look at it more and not jump it.

[Henry Minute]

I have not done anything with encryption for a long time. So this is not guaranteed to work. I think your problem is in the declaration of encrypted. Instead of:

    byte\[\] encrypted = new byte\[130000\];
encrypted =  rsaCSP.Encrypt(toEncrypt, false);

try:

    byte\[\] encrypted = rsaCSP.Encrypt(toEncrypt, false);

After all you do not know in advance the length of the byte-array thet encrypt will return, so why set a length in the declaration. Good luck!

Henry Minute Do not read medical books! You could die of a misprint. - Mark Twain Girl: (staring) "Why do you need an icy cucumber?" “I want to report a fraud. The government is lying to us all.”

[nudma]

I tried that but again

Bad Length

error is at:

byte[] encrypted = rsaCSP.Encrypt(toEncrypt, false);

Please help me out... :(

[Henry Minute]

OK. After a little research. I think the problem might lie in the length of the input. From a little reading it seems that RSACryptoServiceProvider was designed for encrypting cryptographic keys, it gets a bit upset if you ask it to do too much work. A bit like me. There is quite a bit on the web about this problem, and I would suggest that you do a little more research. I Googled "RSACryptoServiceProvider Bad Length", and if you do the same, you might find a solution, but I doubt it. Choose another CryptoServiceProvider, if you are allowed to. I think that will make your life a whole lot easier.

Henry Minute Do not read medical books! You could die of a misprint. - Mark Twain Girl: (staring) "Why do you need an icy cucumber?" “I want to report a fraud. The government is lying to us all.”

[nudma]

Hi Henry!! Thanks for your help...I searched that too...None of the article contains image encryption through RSACryptoserviceprovider. other CryptoServiceProviders are used...