De/Encrypts from stdin to stdout using XTEA in OFB mode

xteapipe.c

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

void xtea_encrypt(unsigned int num_rounds, uint32_t v[2], uint32_t const key[4]) {
    unsigned int i;
    uint32_t v0=v[0], v1=v[1], sum=0, delta=0x9E3779B9;
    for (i=0; i < num_rounds; i++) {
        v0 += (((v1 << 4) ^ (v1 >> 5)) + v1) ^ (sum + key[sum & 3]);
        sum += delta;
        v1 += (((v0 << 4) ^ (v0 >> 5)) + v0) ^ (sum + key[(sum>>11) & 3]);
    }
    v[0]=v0; v[1]=v1;
}

int main(int argc, char *argv[])
{
    if(argc <= 2) { printf("Usage: %s <iv> <key>\n", argv[0]); return 1; }
    if(strlen(argv[1]) != 16) { fprintf(stderr, "IV must be 16 characters\n"); return 1; }
    if(strlen(argv[2]) != 32) { fprintf(stderr, "Key must be 32 characters\n"); return 1; }
    char *temp = malloc(3);
    temp[2] = 0;
    unsigned char i;

    uint8_t* iv = (uint8_t*) malloc(8);
    for(i = 0; i < 8; i++)
    {
        strncpy(temp, (char*) argv[1]+i*2, 2);
        sscanf(temp, "%02x", (unsigned int*) &iv[i]);
    }
    uint8_t* key = (uint8_t*) malloc(16);
    for(i = 0; i < 16; i++)
    {
        strncpy(temp, (char*) argv[2]+i*2, 2);
        sscanf(temp, "%02x", (unsigned int*) &key[i]);
    }
    short pos = 9;
    uint8_t* current = (uint8_t*) malloc(8);
    memcpy(current, iv, 8);

    while(1)
    {
        if(pos == 9)
        {
            xtea_encrypt(32, (uint32_t*) current, (uint32_t*) key);
            pos = 0;
        }
        char c = getc(stdin);
        if(feof(stdin)) break;
        putchar(c ^ current[pos]);
        //fflush(stdout);
        pos++;
    }
    return 0;
}