Takes a linear array of size 16 and converts it into a 4x4 state array - Java Collection Framework

Java examples for Collection Framework:Array Convert

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Description

Takes a linear array of size 16 and converts it into a 4x4 state array

Demo Code


//package com.java2s;
import java.util.zip.DataFormatException;

public class Main {
    public static void main(String[] argv) throws Exception {
        byte[] array = new byte[] { 34, 35, 36, 37, 37, 37, 67, 68, 69 };
        System.out/*from   w  w  w  .j a  v a2 s  .c o  m*/
                .println(java.util.Arrays.toString(arrayTo4xArray(array)));
    }

    /**
     * Takes a linear array of size 16 and converts it into a 4x4 state array
     * As defined in FIPS197
     * 
     * Idea of linearising/squaring arrays taken from watne.seis720.project.AES_Utilities
     * Watne uses array indexes and some unpleasant looking maths, so I've rewritten it
     * to use arraycopy instead, which is much more efficient.
     * 
     * @param array - Linear byte array of length 16
     * @return array - 4x4 2D byte array
     * @throws DataFormatException
     */
    public static byte[][] arrayTo4xArray(byte[] array)
            throws DataFormatException {
        if (array.length != 16)
            throw new DataFormatException("Array must be of length 16");

        byte[][] array4x = new byte[4][4];

        for (int i = 0; i < 4; i++) {
            System.arraycopy(array, (i * 4), array4x[i], 0, 4);
        }

        return array4x;
    }
}

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