>>>>>>>If all this function does is encrypt a password there are lots of examples written in c# out there ( Google is your friend )
>>>>>>
>>>>>>I did but so for I could not find a simple enough c# encrypt function that can be "duplicated" in VFP. You see I need a function that would do the same from VFP and c# end.
>>>>>>Thank you.
>>>>>
>>>>>Presumably you mean that the C# version should be usable with strings already encoded using the VFP cipher library that you mentioned?
>>>>>
>>>>>Al's pointer to Rick's paper is still valid - you could create a small VFP com interop which could be accessed from .net.
>>>>>
>>>>>But which functions of that library do you actually use ? - the core encryption is fairly straightforward.
>>>>>I took a look at the original C code and it would seem that a C# version should be simple enough to implement......
>>>>
>>>>The function cipher() I am using in VFP code is written in VFP; not in C. Maybe Sergey also wrote it in C but the one he recommended to me years ago was the VFP function. To be honest, I don't even understand all VFP functions he used in creating the cipher(). So converting/rewriting it to C# would be a great challenge.
>>>
>>>The VFP code was based on a C conversion and there's a link to the C source - you might find that easier to convert to C# (or not :-} )
>>
>>Do you know where I can find the DLL (I presume tha the C code was built into a DLL) file that uses this C code? And maybe it has the C code there as well.
>
>Does this work (not properly tested and could certainly be improved):

using System;
>using System.Linq;
>using System.Text;
>
>namespace Cipher
>{
>    public class Cipher
>    {
>        private const int PwMinNum = 1000;
>
>        public string Encrypt(string tcStr, string tcPassword)
>        {
>            byte[] tcStrBytes = Encoding.ASCII.GetBytes(tcStr);
>            int tcStrLength = tcStrBytes.Length;
>
>            string lcPassword = tcPassword + '0';
>            byte[] lcPasswordBytes = Encoding.ASCII.GetBytes(lcPassword);
>            int lnPassLen = lcPasswordBytes.Length - 1;
>
>            int lnPassPos = 0;
> 
>            string lcStrOut = string.Empty;
>
>            int lnPassNum = ((CipherGetPnum(lcPassword)/997 - 1)%254) + 1;
>            
>            for (int i = 0; i < tcStrLength;i++)
>            {
>                int lnNum01 = ((lnPassNum + (i - tcStrLength)) - 1);
>                lnPassNum = (Math.Abs(lnNum01)%254)*Math.Sign(lnNum01) + 1;
>                var lnByte = tcStrBytes[i] ^ (lnPassNum ^ lcPasswordBytes[lnPassPos]);
>                lnByte = lnByte & 0xFF;
>                lcStrOut = lcStrOut + (lnByte == 0 ? Convert.ToChar( tcStrBytes[i + 1]) : Convert.ToChar(lnByte));
>                lnPassPos = lnPassPos>=lnPassLen ? 1:lnPassPos + 1;
>            }
>            return lcStrOut;
>        }
>
>        private int CipherGetPnum(string tcStr)
>        {
>            byte[] ascii = Encoding.ASCII.GetBytes(tcStr);
>            int liRet = 1 + ascii.Select((t, i) => t + i).Sum();
>
>            while (liRet < PwMinNum)
>            {
>                liRet = liRet << 1;
>            }
>            return liRet;
>        }
>    }
>}

This is my C# code:

   public class VfpCipher
    {

        public static string Cipher(string cString, string tcPassword)
        {
            string lcPassword;
            int lnPassLen;
            int lnPassPos;
            int iAsciiValue;
            int lnPassNum;
            int lnStrLen;

            lnStrLen = cString.Length; 

            char ChrZero;
            ChrZero = (char)0;

            lcPassword = tcPassword + ChrZero.ToString(); // in VFP this was add CHR(0) to the Password string
            lnPassLen = lcPassword.Length; 

            int[] laPassword = new int[lnPassLen+1];
            for (lnPassPos = 0; lnPassPos < lnPassLen; lnPassPos++)
            {
                // Get one-character from the Password string and store the ASC()/ASCII value of it to the array.
                var charByte = System.Text.Encoding.GetEncoding(1252).GetBytes(lcPassword.Substring(lnPassPos, 1));
                laPassword[lnPassPos] = Convert.ToInt32(charByte[0]);
            }

            // Get seed value
            lnPassNum = (int)((((CipherGetPnum(lcPassword) / 997) - 1) % 254) + 1);

            int lnByte;
            string lcStrOut = "";
            lnPassPos = 0;  // in VFP this is 1 but in C# the array is zero-based.
            int lnNum01;
            
            //  Encode/decode each character
            for (int lnInPos=0; lnInPos < lnStrLen-1; lnInPos++)
            {
                // Get new seed value
                lnNum01 = (( lnPassNum + (lnInPos - lnStrLen)) - 1);
                lnPassNum = ( Math.Abs(lnNum01) % 254 ) * Math.Sign(lnNum01) + 1;

                // Get the character byte and extract the ASCII value of the character.
                var charByte = System.Text.Encoding.GetEncoding(1252).GetBytes(cString.Substring(lnInPos, 1));

                iAsciiValue = Convert.ToInt32(charByte[0]);
                lnByte = (iAsciiValue ^ (lnPassNum ^ laPassword[lnPassPos]));

                // Convert signed value to unsigned, if necessary
	            lnByte = lnByte & 0xFF;
	            
                // If result is zero, use current character
                // Get one character string value of lnByte
                char cOneChar;
                cOneChar = (char)lnByte;
                string sOneChar;
                sOneChar = cOneChar.ToString();
	            lcStrOut = lcStrOut + (lnByte.Equals(0) ? cString.Substring(lnInPos, 1) : sOneChar);

                lnPassPos = (lnPassPos.CompareTo(lnPassLen-1) >= 0 ? 0 : lnPassPos + 1);
            }

            return lcStrOut;

        }

        public static int CipherGetPnum(string SeedString)
        {
            int liRet = 1;
            int iAsciiValue;
            for (int lnPos = 0; lnPos < SeedString.Length; lnPos++)
            {
                var charByte = System.Text.Encoding.GetEncoding(1252).GetBytes(SeedString.Substring(lnPos, 1));
                iAsciiValue = Convert.ToInt32(charByte[0]);
                liRet = liRet + iAsciiValue + lnPos;
            }

            // Note that in Sergey's code the value 1000 is declared as constant.
            do 
            {
                liRet = liRet << 1;
            } while (liRet < 1000);

            return liRet;

        }
    }