Código: Seleccionar todo

import java.util.Random;


public class BASE64Cipher {
	
	
	Random rand = new Random();
	private static final String base64code = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
    private static final int splitLinesAt = 76;
 
    public static byte[] zeroPad(int length, byte[] bytes) {
        byte[] padded = new byte[length];
        System.arraycopy(bytes, 0, padded, 0, bytes.length);
        return padded;
    }
    
    public static String generateString(Random rng, String characters, int length)
    {
        char[] text = new char[length];
        for (int i = 0; i < length; i++)
        {
            text[i] = characters.charAt(rng.nextInt(characters.length()));
        }
        return new String(text);
    }
    
    
    public static String splitLines(String string) {
    	 
        String lines = "";
        for (int i = 0; i < string.length(); i += splitLinesAt) {
 
            lines += string.substring(i, Math.min(string.length(), i + splitLinesAt));
            lines += "\r\n";
 
        }
        return lines;
 
    }
    
    
    public static String decrypt64(String hash)
    {
        String d = new String(decode(hash));
    	return d;
    }
	
	
	public static byte[] decode(String string)
	{
		if (string == null)  return  null;
	    byte data[] = string.getBytes();
	    return decode(data);
	}
	
	public final static byte[] decode(byte[] data)
	  {
	    int tail = data.length;
	    while (data[tail-1] == '=')  tail--;
	    byte dest[] = new byte[tail - data.length/4];
	    
	    for (int idx = 0; idx <data.length; idx++)
	    {
	      if (data[idx] == '=')    data[idx] = 0;
	      else if (data[idx] == '/') data[idx] = 63;
	      else if (data[idx] == '+') data[idx] = 62;
	      else if (data[idx] >= '0'  &&  data[idx] <= '9')
	        data[idx] = (byte)(data[idx] - ('0' - 52));
	      else if (data[idx] >= 'a'  &&  data[idx] <= 'z')
	        data[idx] = (byte)(data[idx] - ('a' - 26));
	      else if (data[idx] >= 'A'  &&  data[idx] <= 'Z')
	        data[idx] = (byte)(data[idx] - 'A');
	    }
	    
	    int sidx, didx;
	    for (sidx = 0, didx=0; didx < dest.length-2; sidx += 4, didx += 3)
	    {
	      dest[didx]   = (byte) ( ((data[sidx] << 2) & 255) |
	              ((data[sidx+1] >>> 4) & 3) );
	      dest[didx+1] = (byte) ( ((data[sidx+1] << 4) & 255) |
	              ((data[sidx+2] >>> 2) & 017) );
	      dest[didx+2] = (byte) ( ((data[sidx+2] << 6) & 255) |
	              (data[sidx+3] & 077) );
	    }
	    if (didx < dest.length)
	    {
	      dest[didx]   = (byte) ( ((data[sidx] << 2) & 255) |
	              ((data[sidx+1] >>> 4) & 3) );
	    }
	    if (++didx < dest.length)
	    {
	      dest[didx]   = (byte) ( ((data[sidx+1] << 4) & 255) |
	              ((data[sidx+2] >>> 2) & 017) );
	    }
	    return dest;
	  }
	
	
	public static String encode64(String string) {
		 
        String encoded = "";
        byte[] stringArray;
        try {
            stringArray = string.getBytes("UTF-8");
        } catch (Exception ignored) {
            stringArray = string.getBytes();
        }
        int paddingCount = (3 - (stringArray.length % 3)) % 3;
        stringArray = zeroPad(stringArray.length + paddingCount, stringArray);
        for (int i = 0; i < stringArray.length; i += 3) {
            int j = ((stringArray[i] & 0xff) << 16) +
                ((stringArray[i + 1] & 0xff) << 8) + 
                (stringArray[i + 2] & 0xff);
            encoded = encoded + base64code.charAt((j >> 18) & 0x3f) +
                base64code.charAt((j >> 12) & 0x3f) +
                base64code.charAt((j >> 6) & 0x3f) +
                base64code.charAt(j & 0x3f);
        }
        return splitLines(encoded.substring(0, encoded.length() -
            paddingCount) + "==".substring(0, paddingCount));
 
    }
}