Question

We want to compute Cyclic Redundancy Check (CRC) for the given the data bits D=110001, generator G=1001, and 3 CRC bits (i.e., r=3),.

Explain the algorithm and implement the CRC computation in a programming language (e.g., C, C++, and Python) with the above setting.

Answer 1

Here I implemented CRC algorithm in C language.

#include <stdio.h>
#include <string.h>
int main()
{
   int i,j,keylen,msglen;
   char input[100],key[30],temp[30],quot[100],rem[30],key1[30];
   printf("Enter Data D: ");
   gets(input);
   printf("Enter Generator G: ");
   gets(key);
   keylen=strlen(key);
   msglen=strlen(input);
   strcpy(key1,key);
   for (i=0;i<keylen-1;i++)
{
       input[msglen+i]='0';
   }
   for (i=0;i<keylen;i++)
   temp[i]=input[i];
   for (i=0;i<msglen;i++)
   {
       quot[i]=temp[0];
       if(quot[i]=='0')
for (j=0;j<keylen;j++)
key[j]='0';
else
for (j=0;j<keylen;j++)
key[j]=key1[j];
       for(j=keylen-1;j>0;j--)
       {
           if(temp[j]==key[j])
           rem[j-1]='0';
else
           rem[j-1]='1';
       }
       rem[keylen-1]=input[i+keylen];
       strcpy(temp,rem);
   }
   strcpy(rem,temp);

   printf("\nRemainder is ");
   for (i=0;i<keylen-1;i++)
   printf("%c",rem[i]);

   printf("\nFinal data is: ");
   for (i=0;i<msglen;i++)
   printf("%c",input[i]);

   for (i=0;i<keylen-1;i++)
   printf("%c",rem[i]);

   return 0;
}

Output :