C# Conversion from Java (Message Digest to Md5CryptoServiceProvider)

Question

I currently have a java program that is creating a MD5 message digest using the following...

MessageDigest dig = MessageDigest.getInstance("MD5");
dig.update(secret);
dig.update(key, offset, len);
return dig.digest();

The problem I am having is that java is using a signed byte array for key and unsigned for secret. How is it possible to change this is C#?

I have the following code in C#:

MD5CryptoServiceProvider md = new MD5CryptoService Provider();
CryptoStream cs = new CryptoStream(Stream.Null, md, CryptoStreamMode.write);
cs.Write(secret, 0, 0);
cs.Write(key, offset, len);
cs.Close();

However secret is a byte[] and key is an sbyte[] to make them the same as in java. I ahave no idea? Any help would be appreciated.

Pankaj Talsania · Answer

Hi AR are you able to convert to C# from JAVA? i am in same boat. I need to convert similar application. I have some problem. let me know. Thx

Alan · Answer

As CryptoStream.Write() takes a byte[] as its first parameter I think you'll just have to convert 'key' from an sbyte[] to a byte[] before calling the method. I think just casting each sbyte element to a byte with overflow checking turned off will probably suffice for cryptography purposes because as the following console app shows the bit representation is maintained when the sbyte contains a negative value (i.e. -1 corresponds to 255 both of which have a bit pattern of 11111111 etc.): using System; class Program { static void Main() { sbyte[] skey = new sbyte[5]{2 1 0-1 -2}; byte[] key = new byte[skey.Length]; for (int i = 0; i { key[i] = unchecked((byte)skey[i]); } foreach(byte b in key) { Console.WriteLine(b); // 2 1 0 255 254 } Console.ReadLine(); } }