Kriptografi : Program C++ Enkripsi dan Deskripsi

Cryptography is the science and an art to maintain the confidentiality of messages (data or information) in a way to disguise it into a form that can not be understood. The purpose encryption is that the content of the message can not be understood by unauthorized people.

Some basic terminology of cryptography :

1.      Plainteks (plaintext or cleartext, meaning the text is clear and understandable): messages are kept confidential.

2.      Chiperteks (ciphertext or cryptogram, meaning encrypted text): encoding the message.

3.      Enkripsi (encryption atau enchipering): encoding process of the plaintext to chiperteks.

4.      Dekripsi (decryption atau dechipering): reversal process of the ciphertext to plain text

5.      Algoritma kriptografi (atau chiper):

Example :

plainteks  : uang disimpan di balik buku X

chiperteks: j&kloP(d$gkhtpuBn%6^klp..t@8^

Mathematical notation

For example:

C = chiperteks

P = plaintext

then the encryption function E mapping P  to C  -->  E(P) = C, and

decryption function D maps C  to P   --> D(C) = P 

Caesar Cipher

Caesar Cipher is an algorithm by substituting characters with other characters.

Substitution table:

p_i : A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

c_i : D E F G H I J K L M N O P Q R S T U V W X Y Z A B C

With each letter of the alphabet to encode an integer as follows: A = 0, B = 1, ..., Z = 25, then mathematically caesar cipher to encrypt the plaintext p_i become c_i with the rules:

c_i = E(p_i) = (p_i + 3) mod 26

and decryption chiperteks c_i  become p_i with rules : p_i = D(c_i) = (c_i – 3) mod 26  

To encrypt or description of the program can be made. We are of the friction with the ASCII code of key. In the example rules above, key = 3. In the program we can use the input from the user how many keys.

This function for encryption :

void kriptografi::enkripsi(){

     for(int i=0; i<strlen(plain); i++){

             chiper[i]=(plain[i]+key)%128;

             }

     cout<<endl<<endl;

     }

    

Here's to a description :

void kriptografi::deskripsi(){

     for (int i=0; i<strlen(chiper); i++){

         teks[i]=(chiper[i]-key)%128;

         }

     }

Complete program to be tried can be downloaded here