Question

Kindly follow the instructions provided carefully.

C programming  

Project 6, Program Design One way to encrypt a message is to use a date’s 6 digits to shift the letters. For example, if a date is picked as December 18, 1946, then the 6 digits are 121846. Assume the dates are in the 20th century. To encrypt a message, you will shift each letter of the message by the number of spaces indicated by the corresponding digit. For example, to encrypt “Hello World” with 121846, the letter H shifts 1 space, making it I; e shifts two spaces, making it g, and so on until you have finished enciphering. The shifted message is “Igmts Cptml”. Note that W shifts 6 spaces, causing you to wrap around back to the beginning of the alphabet, landing at C. Plaintext He 110 W o r 1 d Digits 1 2 1 8 4 6 1 2 1 8 Encrypted Ig ms scpt m1 text Write a program that encrypts a message with a date entered by the user. The plaintext message will be read from a file. The encrypted message will be written to an output file. Example input/output: Enter the file name: input_message.txt Enter date in the format of 6 digit: 121846 Output file name: input_message.txt.ecp

Answer 1

date_encrpyt.c:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
void encrypt(char* message,int date[],int n)
{
int i=0;
for(i=0;i<n;i++)
{
char ch=message[i];
if( ch>='a' && ch<='z' ) //if it is lower
       {
           int cip=(int)ch+date[i%6]; //adding shift
           if(cip>=123) //wrapping aroud
               cip=cip%122 +96;
message[i]=(char)cip;
       }
       if (ch>='A' && ch<='Z') //f it is upper case
{
           int cip=(int)ch+date[i%6]; //adding shift
           if(cip>=91) //wrapping around
               cip=cip%90 +64;
message[i]=(char)cip;
}
}
  
}
int main()
{
   char *msg; //character pointer
char message[10000]; //message array to store line of the file
   FILE *fptr,*fptrout; //pointer to open and write to files
   char inp_filename[100];
   char out_filename[100];
   char dateArr[6];
   int date[6];
   int i;
   //reading input file
   printf("Enter the file name: ");
   scanf("%s",inp_filename);
   if ((fptr = fopen(inp_filename, "r")) == NULL) {
printf("Error! opening file");
exit(1);
}
   //reading date
   printf("Enter date in 6 digit format: ");
   scanf("%s",dateArr);
   for(i=0;i<6;i++)
       date[i]=dateArr[i]-'0';
  

// opening output file for writing message
   fptrout=fopen(strcat(inp_filename,".ecp"),"w");
   if(fptrout == NULL)
{
printf("Unable to create file.\n");
exit(1);
}

  
  
   //encrypting line by line and writing into output file
while (fgets(message,150, fptr)) { //reads a line in one iteration
       msg=message;
       encrypt(msg,date,strlen(message)); //calling encrypt method
       fputs(msg, fptrout); //writing to output file
}
   printf("Output file name: %s\n",strcat(inp_filename,".ecp"));
   fclose(fptr);
   fclose(fptrout);      

return 0;
}

OUTPUT:

En * M 0) 6:42 AM kalyantvk@kalyantvk-Lenovo-G50-80:-/HomeworkLib/HomeworkLib kalyantvkakalyantvk-Lenovo-G50-80:-/HomeworkLib/HomeworkLib$ gcc date_encrypt.c kalyantvk@kalyantvk-Lenovo-G50-80:-/HomeworkLib/HomeworkLib$ ./a.out Enter the file name: input Enter date in 6 digit format: 121846 Output file name: input.ecp.ecp kalyantvk@kalyantvk-Lenovo-G50-80:-/HomeworkLib/HomeworkLib$ 1
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