I use the following two methods to encrypt and decrypt strings:
'Encrypts string. Returns encrypted byte array.
Public Function Encrypt(ByVal str As String) As Byte()
Dim inputInBytes() As Byte = Encoding.Unicode.GetBytes(str)
Dim laesProvider As New AesCryptoServiceProvider()
laesProvider.Key = _key
laesProvider.Mode = CipherMode.CBC
laesProvider.IV = _IV
laesProvider.Padding = PaddingMode.PKCS7
Dim lencryptor As ICryptoTransform = laesProvider.CreateEncryptor
Dim encryptedStream As New MemoryStream
Dim cryptStream As CryptoStream = New CryptoStream(encryptedStream, lencryptor, CryptoStreamMode.Write)
cryptStream.Write(inputInBytes, 0, inputInBytes.Length)
cryptStream.FlushFinalBlock()
encryptedStream.Position = 0
Dim result(encryptedStream.Length - 1) As Byte
encryptedStream.Read(result, 0, encryptedStream.Length)
cryptStream.Close()
Return result
End Function
'Decrypts bytearray. Returns string.
Public Function DecryptToStr(ByVal inputInBytes() As Byte) As String
Dim laesProvider As New AesCryptoServiceProvider()
laesProvider.Key = _key
laesProvider.Mode = CipherMode.CBC
laesProvider.IV = _IV
laesProvider.Padding = PaddingMode.PKCS7
Dim ldecryptor As ICryptoTransform = laesProvider.CreateDecryptor
' Provide a memory stream to decrypt information into
Dim decryptedStream As MemoryStream = New MemoryStream()
Dim cryptStream As CryptoStream = New CryptoStream(decryptedStream, ldecryptor, CryptoStreamMode.Write)
cryptStream.Write(inputInBytes, 0, inputInBytes.Length)
cryptStream.FlushFinalBlock() '#### This is where the exception is thrown ####
decryptedStream.Position = 0
' Read the memory stream and convert it back into a string
Dim result(decryptedStream.Length - 1) As Byte
decryptedStream.Read(result, 0, decryptedStream.Length)
cryptStream.Close()
Return Encoding.Unicode.GetString(result)
End Function
The error occurs when attempting to decrypt certain length strings. When the string is a social security # (11 chars including dashes) then is throws "The input data is not a complete block" CryptographicException. If I pass in for example a string that is exactly 8 characters long, then everything works as expected. I thought that the PKCS7 padding would take care of the various lengths. I'm sure that I'm missing something simple, but after hours of googling, the answer eludes me.
