Program to implement DES (Decryption Encryption Standard)
#include<stdio.h> #include<conio.h> #include<string.h> #include<ctype.h> void main() { char pwd[20]; char alpha[26] = "abcdefghijklmnopqrstuvwxyz"; int num[20], i, n, key; clrscr(); printf("\nEnter the password:"); scanf("%s", &pwd); n=strlen(pwd); for(i = 0; i < n; i++) num[i] = toascii(tolower(pwd[i])) - 'a'; printf("\nEnter the key:"); scanf("%d", &key); for(i = 0; i < n; i++) num[i] = (num[i] + key) % 26; for(i = 0; i < n; i++) pwd[i] = alpha[num[i]]; printf("\nThe key is:%d", key); printf("\nEncrypted text is:%s", pwd); for(i = 0; i < n; i++) { num[i] = (num[i] - key) % 26; if(num[i] < 0) num[i] = 26 + num[i]; pwd[i] = alpha[num[i]]; } printf("\nDecrypted text is:%s", pwd); getch(); }
Output:
Enter the password: geethanjali Enter the key :3 The key is :3 Encrypted text is: jhhwkdqmdol Decrypted text is: geethanjali
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UpdatedNov 05, 2014
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