Simple Atbash Encryptor in C

encrypt.c

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

char atbash_encrypt(char input){
    if(input == ' '){
        return ' ';
    }

    char small_letters[26] = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
    char capital_letters[26] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};

    for(int i=0; i<26; i++){
        if(small_letters[i]==input){
            return small_letters[25-i];
        }
        else if(capital_letters[i]==input){
            return capital_letters[25-i];
        }
    }

    return input; // for the case that input is anything else
}

char* atbash_convert_string(char* s){
    char* final_string = malloc(sizeof(char) * strlen(s));;
    
    for(int i=0; i<strlen(s); i++){
        *(final_string+i) = atbash_encrypt(*(s+i));
    }
    return final_string;
}

void main(){
    // Works both ways, enter original or encrypted text, it will give the opposite
    char* input;
    printf("Enter Text: "); 
    scanf("%[^\n]s",input); // wont break until a new line 

    char* encrypted_text = atbash_convert_string(input);
    printf("\nEncrypted Text is: %s\n",encrypted_text);
}