Envisiontec Ultra 3DP SLA printer/encrypt

EnvisionTEC Ultra Control has a 'Service Mode' that you can activate by entering a 'User code' based off the 'App code' displayed in the program. These are tools to create a valid 'User code' for entering 'Service Mode'. (Only the C++ version has been tested) (the original C# code that decrypts this is on Envisiontec_Ultra_3DP_SLA_printer/encrypt/decrypt

C version by Wilco :

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
 
void SwapCharacter(char * csString, int iPosA, int iPosB)
{
  char ch1 = csString[iPosA];
  char ch2 = csString[iPosB];
  csString[iPosA] = ch2;
  csString[iPosB] = ch1;
}
 
 
int GetNextReturn(int iInitialIndex)
{
  int num;
  do
  {
    ++iInitialIndex;
    num = 2;
    while (num < iInitialIndex && iInitialIndex % num != 0)
      ++num;
  }
  while (num != iInitialIndex);
  return iInitialIndex;
}
 
int GetPrimaryIndex(int iIndex)
{
  int iInitialIndex = 1;
  for (int index = 1; index < iIndex; ++index)
    iInitialIndex = GetNextReturn(iInitialIndex);
  return iInitialIndex;
}
 
char * Decrypt(char * csString)
{
  for (int index = strlen(csString) - 1; index >= 0; --index)
  {
    int iPosB = index;
    int iPosA = GetPrimaryIndex(index + 3) % strlen(csString);
    SwapCharacter(csString, iPosA, iPosB);
  }
  return csString;
}
char * Encrypt(char * csString)
{
  for (size_t index = 0; index < strlen(csString); ++index)
  {
    int iPosB = index;
    int iPosA = GetPrimaryIndex(index + 3) % strlen(csString);
    SwapCharacter(csString, iPosA, iPosB);
  }
  return csString;
}
 
int main(int argc, char **argv) {
    char str[16] = "test";
    if (argc != 2) {
        fprintf(stderr, "Syntax: %s encrypted\n", argv[0]);
        exit(1);
    }
 
    strncpy(str, argv[1], sizeof(str));
    str[sizeof(str)-1] = '\0';
 
    Decrypt(str);
    printf(str);
}

C++ version by RSpliet :

#include <string>
#include <iostream>

using namespace std;
class crypt {
private:
void SwapCharacter(string &csString, int iPosA, int iPosB)
{
	char ch1 = csString[iPosA];
	char ch2 = csString[iPosB];
	csString[iPosA] = ch2;
	csString[iPosB] = ch1;
}

int GetNextReturn(int iInitialIndex)
{
	int num;
	do
	{
		++iInitialIndex;
		num = 2;
		while (num < iInitialIndex && iInitialIndex % num != 0)
			++num;
	} while (num != iInitialIndex);
	return iInitialIndex;
}

int GetPrimaryIndex(int iIndex)
{
	int iInitialIndex = 1;
	for (int index = 1; index < iIndex; ++index)
		iInitialIndex = GetNextReturn(iInitialIndex);
	return iInitialIndex;
}

public:
string Decrypt(string csString)
{
	for (int index = csString.length() - 1; index >= 0; --index) {
		int iPosB = index;
		int iPosA = GetPrimaryIndex(index + 3) % csString.length();
		SwapCharacter(csString, iPosA, iPosB);
	}
	return csString;
}

string Encrypt(string csString)
{
	for (int index = 0; index < csString.length(); index++) {
		int iPosB = index;
		int iPosA = GetPrimaryIndex(index + 3) % csString.length();
		SwapCharacter(csString, iPosA, iPosB);
	}
	return csString;
}

};

int main(int argc, char **argv)
{
	crypt C;
	string cs = C.Encrypt("piehole");
	string ds = C.Decrypt(cs);
	
	cout << cs << endl;
	cout << ds << endl;
	
	return 0;
}

Go version by mrngm :

package main

import (
	"fmt"
)

func Encrypt(s string) string {
	encLen := len(s)
	encBytes := []byte(s)
	for i := 0; i < encLen; i++ {
		oidx := offsetIndex(i + 3)
		newpos := oidx % encLen
		//		fmt.Printf("i: %d (oidx: %d), newpos: %d\n", i, oidx, newpos)
		encBytes[newpos], encBytes[i] = encBytes[i], encBytes[newpos]
	}
	return string(encBytes)
}

func Decrypt(s string) string {
	decLen := len(s)
	decBytes := []byte(s)
	for i := decLen - 1; i >= 0; i-- {
		oidx := offsetIndex(i + 3)
		newpos := oidx % decLen
		//	fmt.Printf("i: %d (oidx: %d), newpos: %d\n", i, oidx, newpos)
		decBytes[newpos], decBytes[i] = decBytes[i], decBytes[newpos]
	}
	return string(decBytes)
}

func offsetIndex(index int) int {
	initial := 1
	for i := 1; i < index; i++ {
		initial = next(initial)
	}
	return initial
}

func next(initial int) int {
	for {
		initial++
		num := 2
		for num < initial && initial%num != 0 {
			num++
		}
		if num == initial {
			break
		}
	}
	return initial
}

func main() {
	fmt.Println(Decrypt(Encrypt("abcdefghijklmnopqrstuvwxyz")))
}