How to Encrypt and Decrypt data in Java

By Atul Rai | Last Updated: July 16, 2018 Previous       Next

In this tutorial we are going to explain how to Encrypt and Decrypt plain text data in a simple way. In this example, we are going to use a simple Key to encrypt the data and the same Key to decrypt the encrypted data.

3 is used as a key to encrypt and decrypt the data.

What is Encryption?

Encryption is a mechanism of encoding the data in such a way that only authorized member can access it. Encode data is called Cipher Text.

What is Decryption?

Decryption is a technique in which we decrypt the encrypted data using same Key that is used while encrypting the data.

Note: In this example we are using the same Key to encrypt and decrypt the data. When the encryption and decryption keys are the same this is called Symmetric key / Private key.

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Encryption Example

In this example, we are going to read the data from PlainText.txt file and apply the encryption key and write the encrypted data in CipherText.txt file.

package org.websparrow;

import java.io.FileInputStream;
import java.io.FileOutputStream;

public class EncryptionExp {
	public static void main(String[] args) {
		try {

			int ctr;

			FileInputStream inputStream = new FileInputStream("PlainText.txt");
			FileOutputStream outputStream = new FileOutputStream("CipherText.txt");

			while ((ctr = inputStream.read()) != -1) {
				ctr -= 3; // 3 is the encryption key .
				System.out.print((char) ctr);
				outputStream.write(ctr);
			}
			outputStream.close();
		} catch (Exception ex) {
			ex.printStackTrace();
		}
	}
}

Output:

Finally, plain text has been encoded as given below…

Tb_Pm^oolt+lodfp^kFkqbokbq`ljm^kv+Fqtfiimolsfabefdenr^ifqv^katbiiqbpqbaqb`ekf`^im^dbpcloFkqbokbqqb`efb+

Decryption Example

This example decrypt the above-encrypted data and write it into OriginalText.txt

package org.websparrow;

import java.io.FileInputStream;
import java.io.FileOutputStream;

class DecryptionExp {
	public static void main(String[] args) {
		try {

			int ctr;

			FileInputStream inputStream = new FileInputStream("CipherText.txt");
			FileOutputStream outputStream = new FileOutputStream("OriginalText.txt");

			while ((ctr = inputStream.read()) != -1) {

				ctr += 3; // 3 is the decryption key.

				System.out.print((char) ctr);
				outputStream.write(ctr);
				Thread.sleep(10);
			}
			outputStream.close();
		} catch (Exception ex) {
			ex.printStackTrace();
		}
	}
}

Output:

Above encode text has been decoded as given below…

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