Could this make Vignere more secure?

I'm wondering if the Vegenere cipher could be more secure if the key generation technique below is used...

In this method, the first key is the SHA-512 hash of the given password. When all 64 bytes of that key have been used, another key is generated, this one being the SHA-512 hash of the previous key. This is repeated until the encryption is complete.

This method is an attempt to foil the Kasiski examination.

The equations for encryption/decryption are:

Ci = Pi + Ki (mod 256)
Pi = Ci - Ki (mod 256)

Which are modified from the original equations so that they can be used on computers with any type of file, not just text.

Edit: Guess I should post the code!

Code:

	public void VigEncryptData(string inFile, string outFile, string password)
	{
		SHA512 hash = new SHA512Managed();

		byte[] key = hash.ComputeHash(System.Text.Encoding.UTF8.GetBytes(password));

		FileStream fin  = new FileStream(inFile, FileMode.Open, FileAccess.Read);
		FileStream fout = new FileStream(outFile, FileMode.OpenOrCreate, FileAccess.Write);

		int i=0, ii=0;

		while(i < fin.Length)
		{
			int c = fin.ReadByte();
			c = (int)(c + key[ii] % 256);
			fout.WriteByte((byte)c);
			if(ii == key.Length-1)
			{
				key = hash.ComputeHash(key);
				ii = 0;
			}
			i++;
			ii++;
		}
		fin.Close();
		fout.Close();
	}

At least standard Vigenère decryption wouldn't work, but I don't know if it'll be much more secure. Why not use a 'standard' well-tested algorithm?

Originally Posted by Sang-drax

At least standard Vigenère decryption wouldn't work, but I don't know if it'll be much more secure. Why not use a 'standard' well-tested algorithm?

I am. My program, so far, uses Rijndael (256-bit key/256-bit blocks) and the Vigenere cipher above.

But Vigenère ciphers aren't secure at all. Instead of trying to enhance it you could use another cipher which has been tested thoroughly.

Originally Posted by Sang-drax

But Vigenère ciphers aren't secure at all. Instead of trying to enhance it you could use another cipher which has been tested thoroughly.

Ok; like I said in my last post, I am using a different cipher (which is the default one in my program).

Why even bother using a Vignere cipher if you're already using Rijndael? It's the current AES cipher, so it's pretty dang secure. (And the math behind it hurts my brain. )

Originally Posted by XSquared

Why even bother using a Vignere cipher if you're already using Rijndael? It's the current AES cipher, so it's pretty dang secure. (And the math behind it hurts my brain. )

My program will have many different ciphers, hopefully. I might add DES/Triple DES, too.

What exactly does your program do?

Originally Posted by XSquared

What exactly does your program do?

It's a file-encryption program. It's availible here.