encryption

#include <stdio.h>
union messageStorage {
    unsigned char segments[sizeof(unsigned long long int)];
    unsigned long long int number;
};
/*
 * Encryption of an original message with replacing
 * neighbour even and odd bytes and further decryption of it
 */
void encryption(union messageStorage ms) {
    char temp;
    // first time for encryption and the second time for decryption
    for (int j = 0; j < 2; j++) {
        for (int i = 0; i < sizeof(ms.number); i += 2) {
            temp = ms.segments[i];
            ms.segments[i] = ms.segments[i+1];
            ms.segments[i+1] = temp;
        }
        if (j == 0) {
            printf("Encrypted message: %lld \n", ms.number);
        } else {
            printf("Decrypted message: %lld \n", ms.number);
        }
    }
}
int main() {
    char temp;
    union messageStorage ms;
    printf("size of t is %lu \n", sizeof(ms.number));
    printf("size of p is %lu \n", sizeof(ms.segments));
    printf("Enter the number: ");
    scanf("%lld", &ms.number);
    printf("Original message: %lld\n", ms.number);
    encryption(ms);
    return 0;
}