Create a class named ShiftRows.java. The code will perform $1$ step of the AES $($Advanced

Encryption Standard$)$ round function.

Background

The Rijndael Algorithm was selected in $2000$ as the Advanced Encryption Standard in the United

States $($See FIPS$197).$ It won a competition against more than $15$ other competing encryption

algorithms.

The algorithm is involved performing several different operations each 'round' $($iteration$)$ to

scramble data. One of the simpler steps in each round is an operation called ShiftRows. The block

being encrypted is $16$ bytes long and it is organized in a $2$ dimensional $(4$xx$4)$ matrix. Each row has a

'circular shift' performed on it by some number of bytes.

The first row is shifted $($rotated$)$ by $0$ bytes $($it is not shifted at all$).$ The second row is shifted by $1$

byte to the left. The third row is shifted by $2$ bytes and the fourth is shifted by $3.$

As an illustration, if the block contained the following before the operation:

After 'ShiftRows', it would be:

You must write a method to implement the ShiftRows operation. It should take a $2$ dimensional

array. It will step through and modify the matrix passed to in place so the calling method will see the

modifications after your shift rows method returns.

Here is the prototype

public static void shiftRows$($char$[][]$ block$)$;

Note very carefully the element type of the matrix. Since the algorithm works with a block of $168-$

bit bytes at a time, we want to make sure the values in the elements do not exceed $255.$ Actually, we

would want to use a byte since that type is $8$ bits but Java forces it to be signed so the value range is

$-128$ through $127,$ not $0$ through $255.$ The next best choice is char which is $16$ bits. This leaves the

problem that values passed in may exceed $255.$ So$,$ before doing the shift operations, check each of

the $16$ values in the matrix and, if any is less than $0$ or greater than $255,$ print an error message

and exit shiftRows$()$ without changing the matrix content. Also, have the shiftRows$()$ method

verify the size of the rows and columns is correct. Otherwise, have it print an error and return

without changing the matrix.

In addition to writing this method, write a method that will print out the $2$ dimensional block in the

form shown above $4$ rows of $4$ columns.

Write a main method that passes in at least two test blocks with different values. Print the block

before and after the call to verify that the code did the right thing.