The Base64 algorithm in action

First we have a base64 mapping table, like below:

Maping table

This is used to get the character for the base64 encrytion.

Now, we try to manually calculate the java.

Get UTF-8 ASCII code

package encryption;

import java.io.UnsupportedEncodingException;

/**
 * encryption.Base64Test
 * <p>
 * Author: ChrisYe
 * Date: 10/8/2017
 */

public class Base64Test {

    public static void main(String... arg) throws UnsupportedEncodingException {
        String testVal = "Java";

        StringBuilder sb = new StringBuilder();
        for(byte b : testVal.getBytes()){
            sb.append(Integer.toString(b)).append(" ");
        }
        System.out.println(sb.toString());
    }

}

So we get the code below:

74 97 118 97

Then we turn the Decimal System to Binary system

Decimal2Binary

Calculate step by step, then we get:

01001010 01100001 01110110 01100001

Turn the Binary system to Base64 code

Binary2Base64

PS:

  1. 6 bit for one base64 code
  2. Must end with 24 bit
  3. Less then 6 bit, low fill with 0
  4. Less then 24, low fill with =

So the Final base64 encrption string is: SmF2YQ==