/*

Tea.cp

A simple C++ implementation of the Tiny Encryption Algorithm (new variant), described here:

[url]http://www.simonshepherd.supanet.com/tea.htm[/url]

The encryption routines have the general form

void encipher(const unsigned long *const v,unsigned long *const w,
   const unsigned long * const k);

void decipher(const unsigned long *const v,unsigned long *const w,
   const unsigned long * const k);

TEA takes 64 bits of data in v[0] and v[1], and 128 bits of key in k[0] - k[3].

The result is returned in w[0] and w[1]. 

*/

#include <cstring>
#include <cstdlib>
#include <iostream>
#include <string>

using namespace std;


//function prototypes

void encipher(const unsigned long *const v,unsigned long *const w, const unsigned long * const k);
void decipher(const unsigned long *const v,unsigned long *const w, const unsigned long * const k);

int main()
	{
	
	// this is the encryption key
	char *key= "1234567890123456";
	
	// this is an unsigned long version of the encryption key which is passed to the encryption algorithm
	unsigned long * l_key=(unsigned long*)key;
	
	// this is the plainText that we want to encrypt
	char *input="Should you ask me,\nwhence these stories?\n"
"Whence these legends and traditions,\nWith the odors of the forest\n"
"With the dew and damp of meadows,\nqwertyuiop1\n"
"Should you ask me,\nwhence these stories?\nWhence these legends and"
"traditions,\nWith the odors of the forest\nWith the dew and damp of"
"meadows,\nqwertyuiop1\noctopus";
	
	// the length of the plainText
	int len=strlen(input);	
	
	// this is an unsigned long version of the text which is passed 
     // to the encryption algorithm
	unsigned long * l_input=(unsigned long*)input;


	//this will be the encrypted text
	char *encryptedText=new char[len];
	// this is the unsigned long version of the encrypted text
    unsigned long * l_encryptedText=(unsigned long*)encryptedText;
    
    
      
    //this will be the decrypted text
	char *decryptedText=new char[len];
	// this is the unsigned long version of the encrypted text
    unsigned long * l_decryptedText=(unsigned long*)decryptedText;
        
    
    // calculate the number of longs in the input lext
    int numberOfPairs = len/8;
	
	cout << "Looping through " << numberOfPairs << " longs" << endl;
	
	// first, encrypt the data 
	
	//loop through the longs, using the encryption algorithm to fill
     //l_encryptedText with an encrypted copy of l_input
	int i;		
    for (i=0; i < numberOfPairs; ++i)
    	{
		encipher( l_input+2*i, l_encryptedText+2*i, l_key);
		}
	
	// pad any extra chars unencrypted
	if(len%8)
		{
		memcpy(l_encryptedText+2*i,l_input+2*i,len%8);
		}
	
	
	//now, decrypt it 
	
	//loop through the longs, using the encryption algorithm to fill
     // l_decryptedText with a decrypted copy of l_encryptedText
    for (i=0; i < numberOfPairs; ++i)
    	{
		decipher( l_encryptedText+2*i, l_decryptedText+2*i, l_key);
		}
	
	// pad any extra chars unencrypted
	if(len%8)
		{
		memcpy(l_decryptedText+2*i,l_encryptedText+2*i,len%8);
		}
	

	cout << "Length of input: " << len << endl;
	
	cout << "Length of encrypted output (should match length of input): " << strlen(encryptedText) << endl;

	cout << endl << endl << encryptedText;
		
	cout << "Length of decrypted output (should match length of input): " << strlen(decryptedText) << endl;
	cout << endl << endl << decryptedText;
	
	
	delete encryptedText;
	delete decryptedText;
	return 0;
	}

/*

These are the functions used in the reference implementation of TEA

*/
	
void encipher(const unsigned long *const v,unsigned long *const w, const unsigned long * const k)
	{
	register unsigned long y=v[0],z=v[1],sum=0,delta=0x9E3779B9,n=32;
	while(n-->0)
		{
		y += (z << 4 ^ z >> 5) + z ^ sum + k[sum&3];
		sum += delta;
		z += (y << 4 ^ y >> 5) + y ^ sum + k[sum>>11 & 3];
		}
	w[0]=y; w[1]=z;
	}

void decipher(const unsigned long *const v,unsigned long *const w, const unsigned long * const k)
	{
	register unsigned long y=v[0], z=v[1], sum=0xC6EF3720, delta=0x9E3779B9, n=32;

	/* sum = delta<<5, in general sum = delta * n */
	while(n-->0)
		{
		z -= (y << 4 ^ y >> 5) + y ^ sum + k[sum>>11 & 3];
		sum -= delta;
		y -= (z << 4 ^ z >> 5) + z ^ sum + k[sum&3];
		}
	w[0]=y; w[1]=z;
	}
	

#include <stdio.h>

int main()
{

  unsigned char *chpoint;
  unsigned long test;
  int i;

  printf("\n\n  sizeof(unsigned long) = %d\n\n", sizeof(unsigned long));
  printf("Conclusions below are based on systems with sizeof(unsigned long) == 4\n\n");
  test = 0x12345678;
  chpoint = (unsigned char *)&test;

  printf(" The bytes are:          ");
  for (i = 0; i < sizeof(unsigned long); i++) {
    printf("0x%02x ", chpoint[i]);
  }
  printf("\n\n\n");
  printf(" If the first byte is 0x12, this system is big-endian\n");
  printf(" If the first byte is 0x78, this system is little-endian\n");


  return 0;
}