Why am I getting a segmentation fault (core Dumped) in a program to encrypt string?

I'm currently learning C programming. This is the C code to encrypt a string.

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

void encrypt(char *message){           // Here message is a character pointer - array
    //char c;
    while(*message){
        *message = *message ^31;
        message++;
    }
}

int main(int argc, char const *argv[])
{
    char *msg = {"Hello Howdy?"};
    encrypt(msg);
    return 0;
}

I'm getting 'Segmentation fault(core dumped)' as the output. It compiles though.