AES Encrypt String in VB.NET

Question

I have a program based in Visual Basic 2010.

I want to use a custom keyword and AES encryption to generate registration keys on our company website, that will unlock the software regardless of whether or not the software is connected to the internet.

To do this, I want to encrypt certain user information (and a validation code) into an AES encrypted string using a utility I'll build on my website. Then, I want my program to decrypt the string into the user information and validation code, then use that information to validate the registration key.

Which brings me to the question - how do I encrypt and decrypt a string in AES programatically? Is there a code template I can use somewhere, or a built in method?

Answer 1

A quick Google Search brings up the following functions: I've not tested whether the output they produce is correct, however they do appear to compile correctly.

Public Function AES_Encrypt(ByVal input As String, ByVal pass As String) As String
        Dim AES As New System.Security.Cryptography.RijndaelManaged
        Dim Hash_AES As New System.Security.Cryptography.MD5CryptoServiceProvider
        Dim encrypted As String = ""
        Try
            Dim hash(31) As Byte
            Dim temp As Byte() = Hash_AES.ComputeHash(System.Text.ASCIIEncoding.ASCII.GetBytes(pass))
            Array.Copy(temp, 0, hash, 0, 16)
            Array.Copy(temp, 0, hash, 15, 16)
            AES.Key = hash
            AES.Mode = Security.Cryptography.CipherMode.ECB
            Dim DESEncrypter As System.Security.Cryptography.ICryptoTransform = AES.CreateEncryptor
            Dim Buffer As Byte() = System.Text.ASCIIEncoding.ASCII.GetBytes(input)
            encrypted = Convert.ToBase64String(DESEncrypter.TransformFinalBlock(Buffer, 0, Buffer.Length))
            Return encrypted
        Catch ex As Exception
        End Try
    End Function

Public Function AES_Decrypt(ByVal input As String, ByVal pass As String) As String
        Dim AES As New System.Security.Cryptography.RijndaelManaged
        Dim Hash_AES As New System.Security.Cryptography.MD5CryptoServiceProvider
        Dim decrypted As String = ""
        Try
            Dim hash(31) As Byte
            Dim temp As Byte() = Hash_AES.ComputeHash(System.Text.ASCIIEncoding.ASCII.GetBytes(pass))
            Array.Copy(temp, 0, hash, 0, 16)
            Array.Copy(temp, 0, hash, 15, 16)
            AES.Key = hash
            AES.Mode = Security.Cryptography.CipherMode.ECB
            Dim DESDecrypter As System.Security.Cryptography.ICryptoTransform = AES.CreateDecryptor
            Dim Buffer As Byte() = Convert.FromBase64String(input)
            decrypted = System.Text.ASCIIEncoding.ASCII.GetString(DESDecrypter.TransformFinalBlock(Buffer, 0, Buffer.Length))
            Return decrypted
        Catch ex As Exception
        End Try
    End Function

Sourced from: http://www.l33thackers.com/Thread-VB-NET-AES-Encryption