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This generates two prime numbers that are large enough to create keys that are in the order of 10’s of millions. It also checks that the numbers are relatively prime to (p-1) * (q – 1) Note that the functions IsPrime, GCD and Euler have not yet been implemented Firstly, create the IsPrime function. VB.NET Private Function IsPrime(ByRef lngNumber As Double) As Boolean On Error Resume Next Dim lngCount As Double Dim lngSqr As Double Dim x As Double lngSqr = Int(System.Math.Sqrt(lngNumber)) ' Get the int square root If lngNumber < 2 Then IsPrime = False Exit Function End If lngCount = 2 IsPrime = True If lngNumber Mod lngCount = 0 Then IsPrime = False Exit Function End If lngCount = 3 For x = lngCount To lngSqr Step 2 If lngNumber Mod x = 0 Then IsPrime = False Exit Function End If Next End Function C# private bool IsPrime(double lngNumber) { double lngCount; double lngSqr; double x; lngSqr = Convert.ToInt64(System.Math.Sqrt(lngNumber)); if (lngNumber < 2) { return false; } lngCount = 2; if (lngNumber % lngCount == 0) { return false; } lngCount = 3; for (x=lngCount;x<lngSqr;x+=2) { if (lngNumber % x == 0) { return false; } } return true; } This function counts from 2 to 3 to the square root of lngNumber in steps of 2. If at any point, an even divisor is found the function returns false. For instance to test the number 101, the function would divide 101 by 2,3,5,7 and 9. Now, to implement Euclid's greatest common divisor algorithm (GCD) function Page 3 Page 5© 2008 Free SMS| Sage Line 50 Component |
