Lab manual

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, CONTENTS

Ex.No Date Name of the Experiment Marks Page Signature
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,EX.NO:1(A) IMPLEMENTATIONOF CAESARCIPHER
DATE:


AIM:
To implement the simple substitution technique named Caesar cipher using C language.

ALGORITHM:
STEP-1: Read the plain text from the user.
STEP-2: Read the key value from the user.
STEP-3: If the key is positive then encrypt the text by adding the key with each character in the plain text.
STEP-4: Else subtract the key from the plain text.
STEP-5: Display the cipher text obtained above.

PROGRAM:
(Caesar Cipher)
#include <stdio.h>
#include <string.h>
#include<conio.h>
#include <ctype.h>
void main(){
char plain[10],
cipher[10];int
key,i,length;
int result;clrscr();
printf("\n Enter the plain text:");
scanf("%s", plain);
printf("\n Enter the key value:");
scanf("%d", &key);
printf("\n \n \t PLAIN TEXt: %s",plain);
printf("\n \n \t ENCRYPTED TEXT: ");
for(i = 0, length = strlen(plain); i < length; i++)
{
cipher[i]=plain[i] + key;
if (isupper(plain[i]) && (cipher[i] > 'Z'))
cipher[i] = cipher[i] - 26;
if (islower(plain[i]) && (cipher[i] > 'z'))
cipher[i] = cipher[i] - 26;
printf("%c", cipher[i]);
}
printf("\n \n \t AFTER DECRYPTION : ");
for(i=0;i<length;i++)
{
plain[i]=cipher[i]-key;
if(isupper(cipher[i])&&(plain[i]<'A'))




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, plain[i]=plain[i]+26;
if(islower(cipher[i])&&(plain[i]<'a'))
plain[i]=plain[i]+26;
printf("%c",plain[i]);
}
getch();
}

Output:




RESULT:

Thus the implementation of Caesar cipher had been executed successfully




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