added symmetric_key_encryption.c in cryptographic algos

Author: codeactic

Cryptographic algos/symmetric_key_encryption.c

@@ -0,0 +1,74 @@
+#include<iostream.h>
+#include<stdio.h>
+#include<string.h>
+#include<stdlib.h>
+int main()
+{ 
+ int key1,key2;
+ char s,wish;
+ int choice;
+ printf("\nExpt No.3 \tSYMMETRIC ENCRYPTION AND DECRYPTION\t18/02/2013");
+ do {
+ cout<<"\n1:Sender side\n2:Receiver side\n3:exit(0)";
+ cout<<"\nEnter your choice:";
+ cin>>choice;
+ 
+ printf("\nAt Sender side:");
+ printf("\nEnter the key:");
+ scanf("%d",&key1);
+
+ printf("\nAt Receiver side:");
+ printf("\nEnter the key:");
+ scanf("%d",&key2);
+ printf("\nEnter the message:");
+  s=getchar();
+ 
+ if(key1==key2)
+ {
+  printf("\nKeys Match..you can proceed communication");
+
+ }
+ else
+ {
+  printf("\nKeys do not match...connection lost.....");
+  exit(0);
+ }
+ switch(choice)
+ {
+ case 1:
+ 
+
+  //  printf("\nEncrypted text is: ");
+    while(s!='\n')
+    {
+     if(s==' ')
+      putchar(s);
+     else
+     {
+      putchar(s+key1);
+     }
+     s=getchar();
+    }
+    putchar(s);
+    break;
+    case 2:
+     
+     while(s!='\n')
+     {
+      if(s==' ')
+       putchar(s);
+      else{
+       putchar(s-key2);
+      }
+      s=getchar();
+     }
+     putchar(s);
+     break;
+    default:
+     exit(0);
+ }
+    printf("\nDo you want to continue communnication:?(y or Y)");
+    scanf("%c",&wish);
+    } while(wish=='y'||wish=='Y');
+  return 0;
+}