I’m trying to XOR the 128 bit Initialization Vector with the Plaintext as seen here
In linux x86-64 gcc 12.2, there’s a one liner
*(unsigned __int128 *)( plaintext ) ^= *(unsigned __int128 *)( ivvectext );
For example, https://godbolt.org/z/sc8e66qeo
#include <stdio.h>
#include <stdint.h>
int main()
{
uint8_t plaintext[16] = {'t','h','e','q','u','i','c','k','b','r','o','w','n','f','o','x'};
uint8_t ivvectext[16] = {'w','a','1','2','o','b','s','q','m','v','c','s','s','q','u','w'};
*(unsigned __int128 *)( plaintext ) ^= *(unsigned __int128 *)( ivvectext );
for (int i = 0; i < sizeof(plaintext); i++) { printf("%02X ", (unsigned char)plaintext[i]); }
return 0;
}
Question
In MSVC, what’s the preferred method to XOR these 128 bit values?
>Solution :
As mentioned in my comment I would use intrincis: Here is how to do it in MSVC:
#include <immintrin.h>
int main() {
uint8_t plaintext[16] = { 't','h','e','q','u','i','c','k','b','r','o','w','n','f','o','x' };
uint8_t ivvectext[16] = { 'w','a','1','2','o','b','s','q','m','v','c','s','s','q','u','w' };
__m128i plain = _mm_loadu_si128((__m128i*)plaintext);
__m128i ivvec = _mm_loadu_si128((__m128i*)ivvectext);
__m128i xored = _mm_xor_si128(plain, ivvec);
return 0;
}
