I'm using Microsoft's [example][1]
  [1]: http://msdn.microsoft.com/en-us/library/ms172831%28v=vs.100%29.aspx
for encrypting/decripting a string. In their example, they are using Tripple DES. I'm trying to convert their code to use AES. 

The modified code, listed below, works. However, I am wondering if I need to change anything in the TruncateHash function or in the AES.Key and AES.IV value. 

This is all new to me, so I am still learning.

    Imports System.Security.Cryptography

    Public NotInheritable Class AesCrypto

    ' Private TripleDes As New TripleDESCryptoServiceProvider
    ' Changed from Triple DES to AES 

    Private AES As New AesCryptoServiceProvider

    Private Function TruncateHash(ByVal key As String, ByVal length As Integer) As Byte()
        ' Creates a byte array of a specified length from the hash of the specified key.

        Dim sha1 As New SHA1CryptoServiceProvider        

        ' Hash the key.
        Dim keyBytes() As Byte = System.Text.Encoding.Unicode.GetBytes(key)
        Dim hash() As Byte = sha1.ComputeHash(keyBytes)

        ' Truncate or pad the hash.
        ReDim Preserve hash(length - 1)
        Return hash
    End Function


    Sub New(ByVal key As String)
        ' Initialize the crypto provider.
        AES.Key = TruncateHash(key, AES.KeySize \ 8)
        AES.IV = TruncateHash("", AES.BlockSize \ 8)
    End Sub

    Public Function EncryptData(ByVal plaintext As String) As String
        ' Encrypt the data.

        ' Convert the plaintext string to a byte array.
        Dim plaintextBytes() As Byte =
            System.Text.Encoding.Unicode.GetBytes(plaintext)

        ' Create the stream.
        Dim ms As New System.IO.MemoryStream
        ' Create the encoder to write to the stream.
        Dim encStream As New CryptoStream(ms,
            AES.CreateEncryptor(),
            System.Security.Cryptography.CryptoStreamMode.Write)

        ' Use the crypto stream to write the byte array to the stream.
        encStream.Write(plaintextBytes, 0, plaintextBytes.Length)
        encStream.FlushFinalBlock()

        ' Convert the encrypted stream to a printable string.
        Return Convert.ToBase64String(ms.ToArray)
    End Function

    Public Function DecryptData(ByVal encryptedtext As String) As String
        'Decrypt the data.

        ' Convert the encrypted text string to a byte array.
        Dim encryptedBytes() As Byte = Convert.FromBase64String(encryptedtext)

        ' Create the stream.
        Dim ms As New System.IO.MemoryStream
        ' Create the decoder to write to the stream.
        Dim decStream As New CryptoStream(ms,
            AES.CreateDecryptor(),
            System.Security.Cryptography.CryptoStreamMode.Write)

        ' Use the crypto stream to write the byte array to the stream.
        decStream.Write(encryptedBytes, 0, encryptedBytes.Length)
        decStream.FlushFinalBlock()

        ' Convert the plaintext stream to a string.
        Return System.Text.Encoding.Unicode.GetString(ms.ToArray)
    End Function

    End Class