gipu/polictf/tea_cversion/tea-decrypt.c

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

void decrypt(uint16_t *v) {
  uint16_t v0 = v[0], v1 = v[1], sum = 0x3780, i; /* set up */
  uint16_t delta = 0x626f;                        /* a key schedule constant */
  uint16_t k0 = 0x7065;                           // "pe"
  uint16_t k1 = 0x7065;                           // "pe"
  uint16_t k2 = 0x7275;                           // "ru"
  uint16_t k3 = 0x6e73;                           // "ns"
  for (i = 0; i < 128; i++) {
    //printf("Intermediate v0: 0x%x | v1: 0x%x\n", v0, v1); /* basic cycle
    // start */
    v1 -= ((v0 << 4) + k2) ^ (v0) ^ ((v0 >> 5) + k3);
    v0 -= ((v1 << 4) + k0) ^ (v1) ^ ((v1 >> 5) + k1);
    sum -= delta;
  } /* end cycle */
  v[0] = v0;
  v[1] = v1;
}

int main(int argc, char *argv[]) {
  uint8_t buf[1000];
  uint32_t buflen, i;

  fprintf(stdout, "Length of the string?\n");
  fflush(stdout);
  fscanf(stdin, "%d", &buflen);
  printf("Length: %d\n", buflen);
  read(0, buf, buflen);

  for (i = 0; i < buflen && i + 2 * (sizeof(uint16_t)) <= buflen;
       i += sizeof(uint32_t)) {
    decrypt((uint16_t *)&buf[i]);
  }
  for (i = 0; i < buflen; i++) {
    fprintf(stdout, "buf[%d] = 0x%02x\n", i, buf[i]);
  }
  printf("STRING: %s\n", buf);
  fflush(stdout);
}