$/*$ Given a Scanner object and a PrintWriter object, copy to the latter

the first four lines of the former.

$*/$

static void processHeader$($Scanner s$,$ PrintWriter w$)$ throws Exception

$\{$

$/*$ To be completed $*/$

$\}//$ processHeader method

Given a file name $($with no extension$)$ for a PGM image and an

AES key $($in hex format$),$ encrypt the image using AES in ECB

mode and store the result in a file whose name is obtained by

adding to the input file name the string $"\_$ECB" $+$ EXT.

$*/$

static void encryptECB$($String filename, String key$)$

$\{$

$/*$ To be completed $*/$

$\}//$ encryptECB method

$/*$ Given a file name $($with no extension$)$ of an encrypted PGM image

and an AES key $($in hex format$),$ decrypt the image using AES in

ECB mode and store the result in a file whose name is obtained

by adding to the input file name the string $"\_$dec" $+$ EXT.

$*/$

static void decryptECB$($String filename, String key$)$

$\{$

$/*$ To be completed $*/$

$//$ decryptECB method

$/*$ given two bit strings of the same length $($represented as int

$*$ arrays whose elements are $0$ or $1),$ return the bit string containing

$*$ the bitwise XOR of the inputs.

$*/$

static int$[]$ xor$($int$[]$ s$1,$ int$[]$ s$2)$

$\{$

int$[]$ returnMe $=$ new int$[128]$;

for$($int i $=0$; i $$ s$1.$length; i$++)\{$

returnMe$[$i$]=$ s$1[$i$]^$ s$2[$i$]$;

$\}$

return returnMe;

$\}//$ xor method

$/*$ Given a $32-$character hex string, return the corresponding

$*128-$bit string represented as an int array in which each

$*$ element is either $0$ or $1.$

$*/$

static int$[]$ hexStringToBits$($String hex$)$

$\{$

return stateToBits$($AES$.$hexStringToByteArray$($hex$))$;

$\}//$ hexStringToBits method

$/*$ Given a file name $($with no extension$)$ for a PGM image, an AES

$*$ key and an initialization vector $($both in hex format$),$ encrypt

$*$ the image using AES in CBC mode and store the result in a file

$*$ whose name is obtained by adding to the input file name the

$*$ string $"\_$CBC$"+$ EXT.

$*/$

static void encryptCBC$($String filename, String key, String IV$)$

$\{$

$/*$ To be completed $*/$

$\}//$ encryptCBC method

$/*$ Given a file name $($with no extension$)$ for an AES$-$encrypted PGM

$*$ image, an AES key and an initialization vector $($both in hex

$*$ format$),$ decrypt the image using AES in CBC mode and store the

$*$ result in a file whose name is obtained by adding to the input

$*$ file name the string $"\_$dec" $+$ EXT.

$*/$

static void decryptCBC$($String filename, String key, String IV$)$

$\{$

$/*$ To be completed $*/$

$\}//$ decryptCBC method

$/*$ Given a file name $($with no extension$)$ for a PGM image, an AES

$*$ key and an initial counter value $($both in hex format$),$ encrypt

$*$ the image using AES in CTR mode and store the result in a file

$*$ whose name is obtained by adding to the input file name the

$*$ string $"\_$CTR$"+$ EXT.

$*/$

static void encryptCTR$($String filename, String key, String counter$)$

$\{$

$/*$ To be completed $*/$

$\}//$ encryptCTR method

$/*$ Given a file name $($with no extension$)$ for an AES$-$encrypted PGM

$*$ image, an AES key and an initialization vector $($both in hex

$*$ format$),$ decrypt the image using AES in CTR mode and store the

$*$ result in a file whose name is obtained by adding to the input

$*$ file name the string $"\_$dec" $+$ EXT.

$*/$

static void decryptCTR$($String filename, String key, String counter$)$

$\{$

$/*$ To be completed $*/$

$\}//$ decryptCTR method