Somebody asked:

I have an application in Java which encrypts data and returns the bytes in a comma separated string, e.g (-22,24,-40,41) Now when I try to convert the same into a byte array for vb.net before decryption I get an error saying "Invalid arithmetic operation". I figured out the reason to be incompatible data type definitions for Bytes in Java and VB .Net A byte in VB .net can store only unsigned values from 0 to 255. Can you suggest a solution?

Yes. As you noticed, the Java byte and the .NET System.Byte are not the same thing.

A Java byte is a signed quantity. The legal range is -127 to 128. The equivalent in .NET is a System.Sbyte. What you need for most of the encryption libraries is an aray of .NET System.Byte, which is an unsigned quantity, with a legal range of 0 to 255.

So what you need to do is convert each element in your string of signed bytes into a System.Sbyte, then convert that array into an array of System.Byte. I am no VB expert, but supposing you start with a string generated on the Java side like this: -24,23,-40,41,56,-2,11,77,52,-13; I think something like this VB code will work:

Public Class ConvertThis

 

  Private Shared Function ArrayOfSbyteToArrayOfByte(sb() as System.Sbyte) as System.Byte()

    Dim b(sb.Length-1) As System.Byte

    Dim b1 as System.Byte

    Dim x as Integer

    For i As Integer = 0 To sb.Length-1

      x= System.Convert.ToInt16(sb(i))

      if (x >= 0 ) then

        b1 =System.Convert.ToByte( sb(i) )

      else

        b1 = System.Convert.ToByte(x+256)

      end if

      b(i)= b1

    Next

    Return b

  End Function

 

 

  Public Shared Sub Main(args() as String)

 

    Dim s as New System.String("-24,23,-40,41,56,-2,11,77,52,-13")

 

    Dim i as Integer

    Dim ss as System.String()

    Dim delimStr As String = " ,"

    Dim delimiter As Char() = delimStr.ToCharArray()

    ss= s.Split(delimiter)

 

    System.Console.WriteLine()

    System.Console.WriteLine("Original string:")

    System.Console.WriteLine("  {0}", s)

 

    System.Console.WriteLine()

    System.Console.WriteLine("As array of sbyte:")

    Dim sb(ss.Length-1) as System.Sbyte

 

    System.Console.Write("  ")

    For i = 0 To ss.Length-1

      sb(i)= System.Sbyte.Parse(ss(i))

      System.Console.Write("{0:D}  ", sb(i))

    Next

 

    System.Console.WriteLine()

    System.Console.WriteLine()

    System.Console.WriteLine("As array of byte:")

 

    Dim b as System.Byte()

    b=ArrayOfSbyteToArrayOfByte(sb)

    System.Console.Write("  ")

    For i = 0 To b.Length-1

      System.Console.Write("{0:X2}  ", b(i))

    Next

    System.Console.WriteLine()

    System.Console.WriteLine()

 

  End Sub

 

End Class

-Dino