从文件中读取单词并在C中逐行加密每个单词

Question

I am fairly new to the C programming language. I would like to seek guidance in encrypting words from a text file and displaying it. Here's what I have done so far. I would like to apologise in advance for the formatting as I'm rather new to stack-overflow.

File-reader1.c is a program I intend to use to read from the text file.

File-reader1.c

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

int main()
{

    FILE *ptr_file;  //declaring a file
    char buf[1000];
    char * hash_type_1 = "$1$";  // md5 hash
    char * hash_type_2 = "$6$";  // sha512 hash
    char * salt_1 ="$";     //a simple salt
    char * result;
    char encyption_scheme[20];

    ptr_file = fopen("small_wordlist","r"); //opening the file
    if (!ptr_file)
        return 1;

    while (fgets(buf,1000, ptr_file) != NULL)
        printf("%s",buf);

    // prepare the first call using md5

    strcpy(encyption_scheme,hash_type_1);
    strcat(encyption_scheme,salt_1);
    result = crypt(buf,encyption_scheme);
    printf("MD5 Result\n");
    printf("%s\n",result);

    // prepare the second call using sha-512 
    strcpy(encyption_scheme,hash_type_2);
    strcat(encyption_scheme,salt_1);
    result = crypt(buf,encyption_scheme);
    printf("SHA-512\n");
    printf("%s\n",result);

    fclose(ptr_file); //closing the file
    return 0;
}

Small_Wordlist is a file containing a list of words I would like to encrypt.

Small_wordlist

Andy 

Noel

Liam

Paul

My output is as follows :

Noel

Liam

Andy

Paul

MD5 Result

$1$$.NeC/EbTUibao2by.HNV01

SHA-512

$6$$qQs5aHFZX/2Iaz4Y1RIihRn./AszpUZnDfld0h5mrWEtAqRJPanIO3cpT3TOOKuFS5hpmLrKAb5MY2mGV2ato1

As you can see. Only one instance of hashing has been done for both SHA 512 and MD5. However, I would like all four words to be hashed with both schemes. Would you be so kind as to walk me through the steps I need to do to accomplish it ? Thank you in advance :)

Answer 1

Chuckling...

What happens if you add a { after

while (fgets(buf,1000, ptr_file)!=NULL)

and a } before

fclose(ptr_file);//closing the file

You are simply reading and outputting buf and only encrypting the final word in the word-list :)

If it is unclear, you look like you intended to do the following:

while (fgets(buf,1000, ptr_file)!=NULL)
{
    printf("%s",buf);

    /* prepare the first call using md5 */
    strcpy(encyption_scheme,hash_type_1);
    strcat(encyption_scheme,salt_1);
    result = crypt(buf,encyption_scheme);
    printf("MD5 Result\n");
    printf("%s\n",result);

    /* prepare the second call using sha-512 */ 
    strcpy(encyption_scheme,hash_type_2);
    strcat(encyption_scheme,salt_1);
    result = crypt(buf,encyption_scheme);
    printf("SHA-512\n");
    printf("%s\n",result);
}

To avoid including the trailing '\\n' (read and included by fgets ) in your encryption, I would recommend removing it before calling crypt using something similar to the following:

#define MAXC 1000
...
    while (fgets(buf,MAXC, ptr_file)!=NULL)
    {
        size_t len = strlen (buf);          /* get length */
        if (len && buf[len - 1] == '\n')    /* check last char '\n' */
            buf[--len] = 0;                 /* overwrite with nul-char */
        else if (len == MAXC - 1) {         /* handle line too long */
            fprintf (stderr, "error: line too long.\n");
            /* handle error as desired */
        }
        printf ("%s\n",buf);

        /* prepare the first call using md5 */
        strcpy(encyption_scheme,hash_type_1);
        strcat(encyption_scheme,salt_1);
        result = crypt(buf,encyption_scheme);
        printf("MD5 Result\n");
        printf("%s\n",result);

        /* prepare the second call using sha-512 */ 
        strcpy(encyption_scheme,hash_type_2);
        strcat(encyption_scheme,salt_1);
        result = crypt(buf,encyption_scheme);
        printf("SHA-512\n");
        printf("%s\n",result);
    }

( note: don't use magic numbers in your code, eg 1000 scattered throughout, instead, if you need a constant, #define one (or more))

look things over and let me know if you have further questions.

Answer 2

At the top of your file, you've read small_wordlist into buf . Then you call crypt , passing buf as the data. This is why the encryption only happens once: buf is being treated as one big string, and all the words are being encrypted together.

In order to change this behavior, you'll need to break buf apart into its composite words. A simple way to do this is to read through the buffer, replacing all whitespace characters with null terminators and saving the index of the start of each word. Then call crypt once for each word encountered, passing buf + i where i is the index of the beginning of the word.

There are, of course, other ways to break buf apart, but the important thing is that you'll need multiple calls to crypt to perform multiple encryptions.