tea64.c

#include <stdio.h>
#include <stdint.h>
#define __STDC_FORMAT_MACROS
#include <inttypes.h> // Needed to print uint64_t, 32, 16... don't need this

uint64_t KEY[4];  // Key space for bit shifts in encryption, decryption functions

void encrypt(uint64_t* v) {
  uint64_t v0=v[0], v1=v[1], sum=0, i;             // set up
  uint64_t delta=0x123457898765432;                // a key schedule constant
  for (i=0; i < 32; i++) {                         // basic cycle start
    sum += delta;
    v0 += ((v1<<4) + KEY[0]) ^ (v1 + sum) ^ ((v1>>5) + KEY[1]);
    v1 += ((v0<<4) + KEY[2]) ^ (v0 + sum) ^ ((v0>>5) + KEY[3]);  
  }                                                // end cycle 
  v[0]=v0; v[1]=v1;
}       

void decrypt (uint64_t* v) {
    uint64_t v0=v[0], v1=v[1], sum=0x2468af130eca8640, i;  // set up 
    uint64_t delta=0x123457898765432;                      // a key schedule constant 
    for (i=0; i<32; i++) {                                 // basic cycle start 
        v1 -= ((v0<<4) + KEY[2]) ^ (v0 + sum) ^ ((v0>>5) + KEY[3]);
        v0 -= ((v1<<4) + KEY[0]) ^ (v1 + sum) ^ ((v1>>5) + KEY[1]);
        sum -= delta;
    }                                                      // end cycle 
    v[0]=v0; v[1]=v1;
}

int main()
{        
		uint64_t v[] = {0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF};
		// 64 bit ASCII->HEX translation of LJBLKECB: 4C4A424C4B454342  
		// 64 bit ASCII->HEX trnaslation of 0CELCIMF: 3043454C43494D46
		
		//delta = 0x1234567898765432 = (1311768467425612850) base 10
		//sum   = 0x468acf130eca8640 = (5083102810200507968) base 10
		//printf("%"PRIu64"\n", sum);

		
		//PRIx64 for hex
		printf(" Original Values: [ ");
		printf("%"PRIx64" ", v[0]);
		printf("%"PRIx64" ] \n", v[1]);

        encrypt(v);
        printf(" Encrypted:       [ ");
		printf("%"PRIx64" ", v[0]);
		printf("%"PRIx64" ] \n", v[1]);

        decrypt(v);
        printf(" Decrypted:       [ ");
		printf("%"PRIx64" ", v[0]);
		printf("%"PRIx64" ] \n", v[1]);
        printf("\n"); 

        return 0;
}