Question

I’m look at algorithms and ways to generating a 10 digit security token. I’ve tried the following:

        RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
        var buffer = new byte[4];
        rng.GetBytes(buffer);
        int result = BitConverter.ToInt32(buffer, 0);
        var token = Math.Abs(result).ToString();

The problem is RNGCryptoServiceProvider seems to return around 9 to 10 digits. I’ve consider add an extra random numbers if it contains less than 10 digits however I not convinced this is the best approach.

appreciate any advice or recommendations.

Answer 1

Just pad the result with zeros to get 10 digits. Also, you should rather use a ulong to get the full range of 10 digits.

var buffer = new byte[8]; // 8 bytes for a long
rng.GetBytes(buffer);
ulong result = BitConverter.ToUInt64(buffer, 0); // unsigned to avoid having to use Abs
var token = result.ToString("D10"); // pads the result to 10 digits
token = token.Substring(token.Length - 10); // strip out extra digits, if any