Encryption - Decrypted File Is Larger Than Source File?

ive been trying to use System.Security.Cryptography to encrypt and decrypt a file but its not working for me

this code

Private Sub EncryptFile(ByVal sInputFilename As String, ByVal sOutputFilename As String, ByVal sKey As String)
Dim fsInput As New FileStream(sInputFilename, FileMode.Open, FileAccess.Read)
Dim fsEncrypted As New FileStream(sOutputFilename, FileMode.Create, FileAccess.Write)
Dim DES As New DESCryptoServiceProvider()

[code]....

called with

DecryptFile(OpenFileDialog1.FileName, SaveFileDialog1.FileName, "12345678")[/CODE]

outputs a file that is almost 2x as large as the source file that was encrypted.