Decompiled C# code from the original binary:
private string Decrypt(string csString)
{
for (int index = csString.Length - 1; index >= 0; --index)
{
int iPosB = index;
int iPosA = this.GetPrimaryIndex(index + 3) % csString.Length;
this.SwapCharacter(ref csString, iPosA, iPosB);
}
return csString;
}
private void SwapCharacter(ref string csString, int iPosA, int iPosB)
{
char[] charArray = csString.ToCharArray();
char ch1 = charArray[iPosA];
char ch2 = charArray[iPosB];
charArray[iPosA] = ch2;
charArray[iPosB] = ch1;
csString = new string(charArray);
}
private int GetPrimaryIndex(int iIndex)
{
int iInitialIndex = 1;
for (int index = 1; index < iIndex; ++index)
iInitialIndex = this.GetNextReturn(iInitialIndex);
return iInitialIndex;
}
private int GetNextReturn(int iInitialIndex)
{
int num;
do
{
++iInitialIndex;
num = 2;
while (num < iInitialIndex && iInitialIndex % num != 0)
++num;
}
while (num != iInitialIndex);
return iInitialIndex;
}