U-FOC/Firmware/STM32G431RB_Bootloader/Core/Src/xtea.c

#include "xtea.h"

void xtea_encrypt(uint32_t v[2], const uint32_t k[4]) {
    uint32_t v0=v[0], v1=v[1], sum=0, delta=0x9E3779B9;
    for (uint8_t i=0;i<32;i++) {
        v0 += (((v1<<4) ^ (v1>>5)) + v1) ^ (sum + k[sum & 3]);
        sum += delta;
        v1 += (((v0<<4) ^ (v0>>5)) + v0) ^ (sum + k[(sum>>11) & 3]);
    }
    v[0]=v0; v[1]=v1;
}

void xtea_decrypt(uint32_t v[2], const uint32_t k[4]) {
    uint32_t v0=v[0], v1=v[1], delta=0x9E3779B9, sum=delta*32;
    for (uint8_t i=0;i<32;i++) {
        v1 -= (((v0<<4) ^ (v0>>5)) + v0) ^ (sum + k[(sum>>11) & 3]);
        sum -= delta;
        v0 -= (((v1<<4) ^ (v1>>5)) + v1) ^ (sum + k[sum & 3]);
    }
    v[0]=v0; v[1]=v1;
}