Initial code, everything seems to be working

Keygen.cs

@@ -0,0 +1,220 @@
+using System;
+using System.Text;
+
+namespace FrappeMocha
+{
+    public class Keygen
+    {
+        private int param_encoding;
+
+        public enum LicenseTypes
+        {
+            License3270 = 140,
+            License5250 = 128,
+            License3812 = 160,
+            LicenseTelnet = 155,
+            LicenseJava3270 = 30,
+            LicenseJava5250 = 30,
+            LicenseJavaTelnet = 0x1b,
+            LicenseMac3270 = 0x5d,
+            LicenseMac5250 = 0x16,
+        }
+
+        public Keygen()
+        {
+            this.param_encoding = 0;
+        }
+
+        public bool CheckLicense(string param_lickey, string param_company, LicenseTypes license)
+        {
+            switch (license)
+            {
+                case LicenseTypes.License3270:
+                case LicenseTypes.License3812:
+                case LicenseTypes.License5250:
+                case LicenseTypes.LicenseTelnet:
+                    return CheckLicenseWindows(param_lickey, param_company, license);
+
+                case LicenseTypes.LicenseJavaTelnet:
+                case LicenseTypes.LicenseJava3270:
+                // case LicenseTypes.LicenseJava5250:
+                    return CheckLicenseJava(param_lickey, param_company, license);
+
+                case LicenseTypes.LicenseMac3270:
+                case LicenseTypes.LicenseMac5250:
+                    return CheckLicenseMac(param_lickey, param_company, license);
+            }
+            return false;
+        }
+
+        public bool CheckLicenseJava(string param_lickey, string param_company, LicenseTypes license)
+        {
+            return true;
+        }
+
+        public bool CheckLicenseMac(string param_lickey, string param_company, LicenseTypes license)
+        {
+            return true;
+        }
+
+        public bool CheckLicenseWindows(string param_lickey, string param_company, LicenseTypes license)
+        {
+            uint num1 = 0;
+            if (param_company == null || param_company.Length < 2)
+                return false;
+            byte[] byteArray = this.StrToByteArray(param_company);
+            if (param_lickey == null || param_lickey.Length < 6)
+                return false;
+            for (int index = 0; index < byteArray.Length; ++index)
+            {
+                // >= 'A' && <= 'Z'
+                if ((int)byteArray[index] >= 65 && (int)byteArray[index] <= 90)
+                    byteArray[index] += (byte)32;
+            }
+            for (int index = 0; index < byteArray.Length; ++index)
+            {
+                if ((int)byteArray[index] >= 65) // 'A'
+                    num1 += (uint)byteArray[index] + (uint)license;
+            }
+            uint num2 = num1 * (uint)param_lickey[0];
+            uint num3 = (uint)((int)num2 * ((int)num2 & (int)byte.MaxValue) & (int)ushort.MaxValue);
+            if (num3 < 100U)
+                num3 = 2728U;
+
+            if (param_lickey.StartsWith((param_lickey[0].ToString() ?? "") + (object)num3))
+            {
+                //this.aa = param_lickey.Substring(0, 1);
+                return true;
+            }
+            //this.aa = "";
+            return false;
+        }
+
+        public string GenLicense(int type, string param_company, LicenseTypes license)
+        {
+            switch (license)
+            {
+                case LicenseTypes.License3270:
+                case LicenseTypes.License3812:
+                case LicenseTypes.License5250:
+                case LicenseTypes.LicenseTelnet:
+                    return GenLicenseWindows(type, param_company, license);
+
+                case LicenseTypes.LicenseJavaTelnet:
+                case LicenseTypes.LicenseJava3270:
+                    // case LicenseTypes.LicenseJava5250:
+                    return GenLicenseJava(type, param_company, license);
+
+                case LicenseTypes.LicenseMac3270:
+                case LicenseTypes.LicenseMac5250:
+                    return GenLicenseMac(type, param_company, license);
+            }
+            return "";
+        }
+
+        public string GenLicenseWindows(int type, string param_company, LicenseTypes license)
+        {
+            string param_lickey = type.ToString();
+            uint num1 = 0;
+            byte[] byteArray = this.StrToByteArray(param_company);
+            for (int index = 0; index < byteArray.Length; ++index)
+            {
+                if ((int)byteArray[index] >= 65 && (int)byteArray[index] <= 90)
+                    byteArray[index] += (byte)32; // this is basically str.toLower()
+            }
+
+            for (int index = 0; index < byteArray.Length; ++index)
+            {
+                if ((int)byteArray[index] >= 65) // 'A'
+                    num1 += (uint)byteArray[index] + (uint)license;
+            }
+            uint num2 = num1 * (uint)param_lickey[0];
+            uint num3 = (uint)((int)num2 * ((int)num2 & (int)byte.MaxValue) & (int)ushort.MaxValue);
+            if (num3 < 100U)
+                num3 = 2728U;
+
+            param_lickey = ((param_lickey[0].ToString() ?? "") + (object)num3) + '-' +
+                           (Int32)(DateTime.UtcNow.Subtract(new DateTime(1970, 1, 1))).TotalSeconds;
+
+
+            return param_lickey;
+        }
+
+        public string GenLicenseJava(int itype, string param_company, LicenseTypes license)
+        {
+            char type = (char)(itype + (int)'A');
+            string param_lickey = type.ToString() + '@';
+            byte[] byteArray = this.StrToByteArray(param_company);
+            uint num1 = 0;
+
+            for (int b = 0; b < byteArray.Length; b++)
+            {
+                if (param_company.ToCharArray()[b] > ' ')
+                    num1 += param_company.ToCharArray()[b] + (uint)license;
+            }
+
+            uint num2 = num1 * (uint)param_lickey[0];
+            uint num3 = (uint)((int)num2 * ((int)num2 & (int)byte.MaxValue) & (int)ushort.MaxValue);
+            param_lickey += (object) num3;
+            return param_lickey;
+        }
+
+        public string GenLicenseMac(int itype, string param_company, LicenseTypes license)
+        {
+            char type = (char)(itype + (int)'a');
+            string param_lickey = type.ToString() + '@';
+            byte[] byteArray = this.StrToByteArray(param_company);
+            uint num1 = 0;
+
+            for (int b = 0; b < byteArray.Length; b++)
+            {
+                if (param_company.ToCharArray()[b] > ' ')
+                    num1 += param_company.ToCharArray()[b] + (uint)license;
+            }
+
+            uint num2 = num1 * (uint)param_lickey[0];
+            uint num3 = (uint)((int)num2 * ((int)num2 & (int)byte.MaxValue) & (int)ushort.MaxValue);
+            param_lickey += (object)num3;
+            return param_lickey;
+        }
+
+        public byte[] StrToByteArray(string str)
+        {
+            try
+            {
+                return Encoding.GetEncoding(this.param_encoding).GetBytes(str);
+            }
+            catch (Exception ex1)
+            {
+                try
+                {
+                    return Encoding.GetEncoding(0).GetBytes(str);
+                }
+                catch (Exception ex2)
+                {
+                    return new byte[1] { (byte)63 };
+                }
+            }
+        }
+
+        public string ByteArrayToStr(byte[] barr, int index, int length)
+        {
+            try
+            {
+                return Encoding.GetEncoding(this.param_encoding).GetString(barr, index, length);
+            }
+            catch (Exception ex1)
+            {
+                try
+                {
+                    return Encoding.GetEncoding(0).GetString(barr, index, length);
+                }
+                catch (Exception ex2)
+                {
+                    return "?";
+                }
+            }
+        }
+
+    }
+}