$```$

$/*$ 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

$```$