Encrypting binary files

[FaisalJ]

I am encrypting files. Teh brief code is:

RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();

// some code to set rsa skiped here


// input buffer
byte[] inbuf = new byte[(new FileInfo(fileName)).Length];

//output buffer
byte[] outbuf = null;

//stream
FileStream fs = File.OpenRead(fileName);

// read the file
fs.Read(inbuf,0, inbuf.Length);
fs.Close();
outbuf = rsa.Encrypt(inbuf,false);


//write to output file

fs = File.OpenWrite(outputFile);
fs.Write(outbuf,0,outbuf.Length);
fs.Close();



Now when the input file is a text file its works ok
but when thefile is a binay file (a Serialized file to be exact)
the outbuf = rsa.Encrypt(inbuf,false); crashes giving the error "bad length"

not that the binay file if opned in notpad has chracters like

 

Soo....whats wrong with length here ???

Thanks!

[Holiday]

Originally posted by FaisalJ
Now when the input file is a text file its works ok
but when thefile is a binay file (a Serialized file to be exact)
the outbuf = rsa.Encrypt(inbuf,false); crashes giving the error "bad length"

Assuming that the crash is due to the wrong public key a CryptographicException is thrown.
If you use RSA, you have first to provide the generated public Key, which is used to encrypt the file, after transmission you can decrypt the file. You can forward the generated public key as a string by using

pubKey = rsa.ToXmlString(false);

after providing this key, you use it with

RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
rsa.FromXmlString(publicKey_Client);

-then performing with this pubKey the encryption
-transfer the encrypted byte[]
-decrypt

Hope that helps