JavaTutorial #12 :How to encrypt and descrypt txt file with AES in ...

JavaTutorial #12 :How to encrypt and descrypt txt file with AES in ... | Ecency

Repository

https://github.com/dmlloyd/openjdk

What Will I Learn?

You will learn about AES
You will learn how to encrypt and descrypt file with AES
You will learn how to implement this cryptography in java programing

Requirements

-NetBeans IDE Software

Basic Knowledge about Java Programing and Netbeans

Difficulty

Basic

Tutorial Contents

The Advanced Encryption Standard (AES) is a standard symmetric key-encryption adopted by the United States government. It consists of 3 block ciphers, namely AES-128, AES-192 and AES-256, which are adopted from larger collections that were originally published as Rijndael. Each cipher has a 128-bit size, with a key size of 128, 192 and 256 bits, respectively. AES has been widely analyzed and is now used throughout the world, as is the case with its predecessor, Data Encryption Standard (DES).

Here we will try to implement the AES method to encrypt and decrypt txt files. You need to know that in the encryption process there are 2 components, Plaintext and Chipper. The plaintext is the original text before it is encrypted and after the description. While Chipper is text that has been encrypted and cannot be read anymore. This encryption and description process uses certain keywords called secretkey.

Now, Let's try to implement it in Java Programing

Preparation

Create a new txt file that contain some text
Open Netbeans IDE then create new project
Choose java Aplication then click next
Set project name and location and click finish

Start Coding

Open java class from your project
Add this code throws IOException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException after (String[] args). This code used to handle some error that will be happen later in our program
Left Click on warning lamp simbol beside the code
Click all add import until the error simbol doesn't exist anymore
Load the txt file that you have created before.Put the code bellow in public main
byte[] array = Files.readAllBytes(new File("D:\\before.txt").toPath());
all texts in before.txt are converted to array
After loading the file, Now we encrypt it using aes method. To encrypt some text with aes we need a secretkey, like code bellow :

                byte [] secKey=new byte[]{'1','2','3','4','m','m','a','d','r','i','z','k','a','a','j','0'};
                SecretKeySpec aesKey=new SecretKeySpec(secKey,"AES");
                Cipher cipher= Cipher.getInstance("AES/ECB/PKCS5Padding");
                cipher.init(Cipher.ENCRYPT_MODE, aesKey);               
                byte[] encrypted = cipher.doFinal(array);

byte [] secKey : secret key
SecretKeySpec aesKey=new SecretKeySpec(secKey,"AES"); : combine secretkey with AES
Cipher cipher= Cipher.getInstance("AES/ECB/PKCS5Padding"); : creating a chipper
cipher.init(Cipher.ENCRYPT_MODE, aesKey); : encryption process
byte[] encrypted = cipher.doFinal(array); :accommodate data that has been encrypted into variable

If you get some error notificaton, left click and import all package that suggest by aplication
display chipper text in new txt file

OutputStream out=new FileOutputStream("D:\\chiper.txt");           
out.write(encrypted);

OutputStream out=new FileOutputStream("D:\\chiper.txt"); : create new txt file
out.write(encrypted); : write data tha has been encrypted in chiper file

Now descrypt the file, before descryption you need to read the chipper first.

byte[] cipherFile = Files.readAllBytes(new File("D:\\paste.pdf").toPath());

descrypt the chipper file.

cipher.init(Cipher.DECRYPT_MODE, aesKey);

Accommodate tha chipper file in a variable

byte[] dekripsi = cipher.doFinal(cipherFile);

create new txt file

OutputStream outputDekripsi=new FileOutputStream("D:\\dekriptedfile.txt");

write all data that has been encrypted in dekriptedfile.txt

outputDekripsi.write(dekripsi);
out.flush();

Running the project

save all file and try to run
now open the location of before.txt , you can see now there is new file. It's chipper.txt and descriptedfile.txt
Open chipper.txt and descriptedfile.txt
success