Dim encrypt As New XceedEncryptionLib.XceedEncryptionClass() 

encrypt.License( "your license key" ) 

Dim rijndael As New XceedEncryptionLib.XceedRijndaelEncryptionMethodClass()
Dim source As Object = "This is the data to encrypt"

Try
  rijndael.SetSecretKeyFromPassPhrase( "This is a weak pass phrase", 128 )
  encrypt.EncryptionMethod = rijndael      

  Dim encryptedData As Object = encrypt.Encrypt( source, true ) 
Catch except As System.Runtime.InteropServices.COMException
  MessageBox.Show( except.ToString() )
End Try 

Dim encrypt As New XceedEncryptionLib.XceedEncryptionClass() 

encrypt.License( "your license key" ) 

Dim rijndael As New XceedEncryptionLib.XceedRijndaelEncryptionMethodClass() 

Try
  rijndael.SetSecretKeyFromPassPhrase( "This is a weak pass phrase", 128 )
  encrypt.EncryptionMethod = rijndael

  Dim decryptedData As Object = encrypt.Decrypt( encryptedData, true ) 

  MessageBox.Show( System.Text.Encoding.Unicode.GetString( CType( decryptedData, Byte() ) ) )
Catch except As System.Runtime.InteropServices.COMException
  MessageBox.Show( except.ToString() )
End Try