Can't figure out what the error is here
Can you please help me figure out what the error is here, in this
rotor cipher simulator, which I wrote to amuse myself? The runtime
error is that it isn't symmetrical --decrypting a piece of ciphertext
w/ the encrypting key doesn't result in the original message--, which
I'm assuming is linked to a coding error. I've spent hours pouring
over this code, and I can't find anything. I must be missing
something...something subtle. Here's the code:
Enigma.hpp
-------------------------------
#ifndef ENIGMA_HPP
#define ENIGMA_HPP
#include <iostream>
#include <string>
using namespace std;
class Error{};
class Rotor
{
public:
Rotor(char pos=0):CurPos(0),steps(0)
{
memcpy(Alphabet,"ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789",36);
SetRotorPosition(CharacterMap(pos));
}
int GetSteps()const{return steps;}
static int CharacterMap(char the_char)
{
static const char *alphabet =
"ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
const char* p;
if (p=strchr(alphabet, the_char))
return (p-alphabet);
else
throw Error();
}
void SetRotorPosition(int NewPos)
{
while(NewPos < 0)
{
NewPos+=36;
}
CurPos=NewPos%36;
steps=0;
}
void AdvanceRotor(int Steps)
{
CurPos += Steps;
while(CurPos < 0)
{
CurPos +=36;
}
CurPos %=36;
steps+=Steps%36;
}
void ReverseRotor(int Steps)
{
AdvanceRotor(-Steps);
}
char GetCurrentCharacter()const
{
return Alphabet[CurPos];
}
char GetCharacterIndex(int Index)const
{
return Alphabet[(CurPos+Index)%36];
}
char GetCharacterInverse(int i)const
{
if (i>=CurPos)
return Alphabet[i - CurPos];
else
return Alphabet[36 + i - CurPos];
}
private:
char Alphabet[36];
int CurPos;
int steps;
};
class Enigma
{
public:
Enigma(char r1,char r2,char r3,char r4,char r5,char r6,char r7,char
r8,char r9,char r10):
R1(r1),R2(r2),R3(r3),R4(r4),R5(r5),R6(r6),R7(r7),R8(r8),R9(r9),R10(r10)
{
memcpy(Reflector,"COAYIWV7E3809TBUZ26NPGF4DQL5RJX1SHKM",36);
}
~Enigma(){}
string Encrypt(const string& cleartext);
string Decrypt(const string& ciphertext);
private:
char plugboard(char input);
Rotor R1;
Rotor R2;
Rotor R3;
Rotor R4;
Rotor R5;
Rotor R6;
Rotor R7;
Rotor R8;
Rotor R9;
Rotor R10;
char Reflector[36];
};
#endif
-------------------------
Enigma.cpp
-------------------------
#include "Enigma.hpp"
#include <string>
using namespace std;
char Enigma::plugboard(char Char)
{
if(Char=='A')
return '0';
else if(Char=='B')
return 'Q';
else if(Char=='C')
return 'W';
else if(Char=='D')
return 'E';
else if(Char=='E')
return 'D';
else if(Char=='F')
return 'T';
else if(Char=='G')
return 'Y';
else if(Char=='H')
return 'U';
else if(Char=='I')
return 'I';
else if(Char=='J')
return 'O';
else if(Char=='K')
return 'P';
else if(Char=='L')
return 'S';
else if(Char=='M')
return 'N';
else if(Char=='N')
return 'M';
else if(Char=='O')
return 'J';
else if(Char=='P')
return 'K';
else if(Char=='Q')
return 'B';
else if(Char=='R')
return 'Z';
else if(Char=='S')
return 'L';
else if(Char=='T')
return 'F';
else if(Char=='U')
return 'H';
else if(Char=='V')
return 'X';
else if(Char=='W')
return 'C';
else if(Char=='X')
return 'V';
else if(Char=='Y')
return 'G';
else if(Char=='Z')
return 'R';
else if(Char=='0')
return 'A';
else if(Char=='1')
return '9';
else if(Char=='2')
return '8';
else if(Char=='3')
return '7';
else if(Char=='4')
return '6';
else if(Char=='5')
return '5';
else if(Char=='6')
return '4';
else if(Char=='7')
return '3';
else if(Char=='8')
return '2';
else if(Char=='9')
return '1';
}
string Enigma::Encrypt(const string& cleartext)
{
string ciphertext;
ciphertext.resize(cleartext.size());
unsigned int i=0;
for(;i<cleartext.length();i++)
{
int val=Rotor::CharacterMap(plugboard(cleartext[i]));
if (val<36)
{
char val1 = R1.GetCharacterIndex(val);
int val2 = Rotor::CharacterMap(val1);
char val3 = R2.GetCharacterIndex(val2);
int val4 = Rotor::CharacterMap(val3);
char val5 = R3.GetCharacterIndex(val4);
int val6 = Rotor::CharacterMap(val5);
char val7 = R4.GetCharacterIndex(val6);
int val8 = Rotor::CharacterMap(val7);
char val9=R5.GetCharacterIndex(val8);
int val10 = Rotor::CharacterMap(val9);
char val11=R6.GetCharacterIndex(val10);
int val12=Rotor::CharacterMap(val11);
char val13=R7.GetCharacterIndex(val12);
int val14=Rotor::CharacterMap(val13);
char val15=R8.GetCharacterIndex(val14);
int val16=Rotor::CharacterMap(val15);
char val17=R9.GetCharacterIndex(val16);
int val18=Rotor::CharacterMap(val17);
char val19=R10.GetCharacterIndex(val18);
int val20=Rotor::CharacterMap(val19);
char val21 = Enigma::Reflector[val20];
int val22 = Rotor::CharacterMap(val21);
char val23 = R10.GetCharacterInverse(val22);
int val24 = Rotor::CharacterMap(val23);
char val25 = R9.GetCharacterInverse(val24);
int val26 = Rotor::CharacterMap(val25);
char val27 = R8.GetCharacterInverse(val26);
int val28 = Rotor::CharacterMap(val27);
char val29 = R7.GetCharacterInverse(val28);
int val30 = Rotor::CharacterMap(val29);
char val31 = R6.GetCharacterInverse(val30);
int val32=Rotor::CharacterMap(val31);
char val33=R5.GetCharacterIndex(val32);
int val34=Rotor::CharacterMap(val33);
char val35=R4.GetCharacterIndex(val34);
int val36=Rotor::CharacterMap(val35);
char val37=R3.GetCharacterIndex(val36);
int val38=Rotor::CharacterMap(val37);
char val39=R2.GetCharacterIndex(val38);
int val40=Rotor::CharacterMap(val39);
char val41=R1.GetCharacterIndex(val40);
ciphertext[i] = plugboard(val41);
R1.AdvanceRotor(1);
if((R1.GetSteps()%36)==0)
{
R2.AdvanceRotor(1);
if((R2.GetSteps()%36)==0)
{
R3.AdvanceRotor(1);
if((R3.GetSteps()%36)==0)
{
R4.AdvanceRotor(1);
if((R4.GetSteps()%36)==0)
R5.AdvanceRotor(1);
{
if((R5.GetSteps()%36)==0)
R6.AdvanceRotor(1);
{
if((R6.GetSteps()%36)==0)
R7.AdvanceRotor(1);
{
if((R7.GetSteps()%36)==0)
R8.AdvanceRotor(1);
{
if((R8.GetSteps()%36)==0)
R9.AdvanceRotor(1);
{
if((R9.GetSteps()%36)==0)
R10.AdvanceRotor(1);
}
}
}
}
}
}
}
}
}
else ciphertext[i]=cleartext[i];
}
return ciphertext;
}
---------------------------------------
EnigmaMain.cpp
----------------------------------
#include "Enigma.hpp"
#include <iostream>
#include <string>
using namespace std;
int main()
{
start:
bool mode;
cout << "Encrypt or decrypt?[Encrypt=1|Decrypt=0]: " << endl;
cin >> mode;
try
{
if(mode==1)
{
cout << "Enter the rotor settings: " << endl;
char R1,R2,R3,R4,R5,R6,R7,R8,R9,R10;
cin >> R1 >> R2 >> R3 >> R4 >> R5 >> R6 >> R7 >> R8 >> R9 >> R10;
Enigma encryptor(R1,R2,R3,R4,R5,R6,R7,R8,R9,R10);
cin.ignore(1);
string cleartext;
cout << "Enter cleartext: " << endl;
getline(cin,cleartext);
string ciphertext(encryptor.Encrypt(cleartext));
cout << "Ciphertext: " << ciphertext << endl;
}
if(mode==0)
{
cout << "Enter the rotor settings: " << endl;
char R1,R2,R3,R4,R5,R6,R7,R8,R9,R10;
cin >> R1 >> R2 >> R3 >> R4 >> R5 >> R6 >> R7 >> R8 >> R9 >> R10;
Enigma decryptor(R1,R2,R3,R4,R5,R6,R7,R8,R9,R10);
cin.ignore(1);
string ciphertext;
cout << "Enter ciphertext: " << endl;
getline(cin,ciphertext);
string cleartext(decryptor.Encrypt(ciphertext));
cout << "Cleartext: " << cleartext << endl;
}
goto start;
}
catch(Error& obj)
{
cout << "Error. \a" << endl;
goto start;
}
return 0;
}
-------------------------------------------
BTW, how secure do you believe this cipher to be, bitwise?
Thank you ever so much!