#!perl
use Math::BigInt;
use MIME::Base64;
use Data::Dumper;

$Data::Dumper::Maxdepth = 3; # no deeper than 3 refs down
#$Data::Dumper::Pair = " : ";
$Data::Dumper::Indent = 0;
$Data::Dumper::Deparse = 1;
$Data::Dumper::Terse = 1;

use POSIX qw(floor strftime mktime setlocale ceil);
#use warnings qw(uninitialized);
my $globaldebug = 1;

#Test1: This is perl, v5.10.1 built for MSWin32-x86-multi-thread
#
#Error: Out of memory!
#

my $nBits = 256;
my $password = 'Ready to Have Some Fun';
my $ciphertext = 'DzQPUdLS0tKCWf9U6V/UDB3aQEUWCQ==';

print decrypt($ciphertext, $password, $nBits) . "\n";
exit;

# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
#  AES counter (CTR) mode implementation in PHP (c) Chris Veness 2005-2011. Right of free use is */
#    granted for all commercial or non-commercial use under CC-BY licence. No warranty of any    */
#    form is offered.                                                                            */
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
  
# 
# Encrypt a text using AES encryption in Counter mode of operation
#  - see http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf
#
# Unicode multi-byte character safe
#
# @param plaintext source text to be encrypted
# @param password  the password to use to generate a key
# @param nBits     number of bits to be used in the key (128, 192, or 256)
# @return          encrypted text
#

# sBox is pre-computed multiplicative inverse in GF(2^8) used in subBytes and keyExpansion [§5.1.1]
my @sBox = (
	0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,
	0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,
	0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,
	0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,
	0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,
	0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,
	0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,
	0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,
	0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,
	0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,
	0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,
	0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,
	0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,
	0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,
	0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,
	0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16
);

# rCon is Round Constant used for the Key Expansion [1st col is 2^(r-1) in GF(2^8)] [§5.2]
my @rCon = ( 
	(0x00, 0x00, 0x00, 0x00),
	(0x01, 0x00, 0x00, 0x00),
	(0x02, 0x00, 0x00, 0x00),
	(0x04, 0x00, 0x00, 0x00),
	(0x08, 0x00, 0x00, 0x00),
	(0x10, 0x00, 0x00, 0x00),
	(0x20, 0x00, 0x00, 0x00),
	(0x40, 0x00, 0x00, 0x00),
	(0x80, 0x00, 0x00, 0x00),
	(0x1b, 0x00, 0x00, 0x00),
	(0x36, 0x00, 0x00, 0x00) 
); 

#
# AES Cipher function: encrypt 'input' with Rijndael algorithm
#
# @param input message as byte-array (16 bytes)
# @param w     key schedule as 2D byte-array (Nr+1 x Nb bytes) - 
#              generated from the cipher key by keyExpansion()
# @return      ciphertext as byte-array (16 bytes)
#
sub cipher {    # main cipher function [§5.1]
	my($input, $w) = @_;
	my @w = @$w;
	#print Dumper(@w) . "\n";
	#exit;

	my @input = @$input;
	my $Nb = 4;                 # block size (in words): no of columns in state (fixed at 4 for AES)
	my $Nr = scalar(@w)/$Nb - 1; # no of rounds: 10/12/14 for 128/192/256-bit keys
	#print $Nr . "\n";

	my @state = ();  # initialise 4xNb byte-array 'state' with input [§3.4]
	for(my $i=0; $i<4*$Nb; $i++){
		$state[$i%4][floor($i/4)] = $input[$i];
		#print $input[$i] . "\n" if($globaldebug == 1);
	}

	my $state = addRoundKey(\@state, \@w, 0, $Nb);
	@state = @$state;

	for(my $round=1; $round<$Nr; $round++) {  # apply Nr rounds
		$state = subBytes(\@state, $Nb);
		@state = @$state;
		$state = shiftRows(\@state, $Nb);
		@state = @$state;
		$state = mixColumns(\@state, $Nb);
		@state = @$state;
		$state = addRoundKey(\@state, \@w, $round, $Nb);
		@state = @$state;
	}
	$state = subBytes(\@state, $Nb);
	@state = @$state;
	$state = shiftRows(\@state, $Nb);
	@state = @$state;
	$state = addRoundKey(\@state, @w, $Nr, $Nb);
	@state = @$state;

	my @output = (4*$Nb);  # convert state to 1-d array before returning [§3.4]
	for (my $i=0; $i<4*$Nb; $i++){
		$output[$i] = $state[$i%4][floor($i/4)];
	}
	#print join(", ",@output) . "\n";
	#exit;

	return \@output;
}

sub addRoundKey {  # xor Round Key into state S [§5.1.4]
	my($state, $w, $rnd, $Nb) = @_;
	my @w = @$w;
	my @state = @$state;
	#print Dumper(@state) . "\n";
	#print Dumper(@w) . "\n";
	for (my $r=0; $r<4; $r++) {
		for (my $c=0; $c<$Nb; $c++){
			$state[$r][$c] ^= $w[$rnd*4+$c][$r];
			#print $state[$r][$c] . "\n";
		}
	}
	#print Dumper(@state) . "\n";
	#exit;
	return \@state;
}
  
sub subBytes {    # apply SBox to state S [§5.1.1]
	my($s, $Nb) = @_;
	my @s = @$s;

	my @sBox = (
		0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,
		0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,
		0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,
		0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,
		0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,
		0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,
		0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,
		0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,
		0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,
		0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,
		0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,
		0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,
		0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,
		0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,
		0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,
		0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16
	);

	for (my $r=0; $r<4; $r++) {
		for (my $c=0; $c<$Nb; $c++){
			$s[$r][$c] = $sBox[$s[$r][$c]];
		}
	}
	return \@s;
}
  
sub shiftRows {    # shift row r of state S left by r bytes [§5.1.2]
	my($s, $Nb) = @_;
	my @s = @$s;
	my @t = (4);#array
	for (my $r=1; $r<4; $r++) {
		for(my $c=0; $c<4; $c++){
			$t[$c] = $s[$r][($c+$r)%$Nb];  # shift into temp copy
		}
		for(my $c=0; $c<4; $c++){
			$s[$r][$c] = $t[$c];           # and copy back
		}
	}# note that this will work for Nb=4,5,6, but not 7,8 (always 4 for AES):
	return \@s;  # see fp.gladman.plus.com/cryptography_technology/rijndael/aes.spec.311.pdf 
}
  
sub mixColumns {   # combine bytes of each col of state S [§5.1.3]
	my($s, $Nb) = @_;
	my @s = @$s;
	for(my $c=0; $c<4; $c++) {
		my @xa = (4);  # 'a' is a copy of the current column from 's'
		my @xb = (4);  # 'b' is a•{02} in GF(2^8)
		for(my $i=0; $i<4; $i++) {
			$xa[$i] = $s[$i][$c];
			$xb[$i] = $s[$i][$c]&0x80 ? $s[$i][$c]<<1 ^ 0x011b : $s[$i][$c]<<1;
		}

		# a[n] ^ b[n] is a•{03} in GF(2^8)
		$s[0][$c] = $xb[0] ^ $xa[1] ^ $xb[1] ^ $xa[2] ^ $xa[3]; # 2*a0 + 3*a1 + a2 + a3
		$s[1][$c] = $xa[0] ^ $b[1] ^ $xa[2] ^ $xb[2] ^ $xa[3]; # a0 * 2*a1 + 3*a2 + a3
		$s[2][$c] = $xa[0] ^ $xa[1] ^ $xb[2] ^ $xa[3] ^ $xb[3]; # a0 + a1 + 2*a2 + 3*a3
		$s[3][$c] = $xa[0] ^ $b[0] ^ $xa[1] ^ $xa[2] ^ $xb[3]; # 3*a0 + a1 + a2 + 2*a3
	}
	return \@s;
}

#
# Key expansion for Rijndael cipher(): performs key expansion on cipher key
# to generate a key schedule
#
# @param key cipher key byte-array (16 bytes)
# @return    key schedule as 2D byte-array (Nr+1 x Nb bytes)
#
sub keyExpansion {  # generate Key Schedule from Cipher Key [§5.2]
	my($key) = @_;
	my @key = @$key;
	my $Nb = 4;              # block size (in words): no of columns in state (fixed at 4 for AES)
	my $Nk = scalar(@key)/4;  # key length (in words): 4/6/8 for 128/192/256-bit keys
	my $Nr = $Nk + 6;        # no of rounds: 10/12/14 for 128/192/256-bit keys

	my @w = ();#array
	for(my $i=0; $i<$Nb*($Nr+1); $i++){
		$w[$i] = 0;
	}
	my @temp = ();#array
	for(my $i=0; $i<4; $i++){
		$temp[$i] = 0;
	}

	for(my $i=0; $i<$Nk; $i++) {
		my @r = ($key[4*$i], $key[4*$i+1], $key[4*$i+2], $key[4*$i+3]);
		$w[$i] = [@r];
	}

	my @rCon = ( 
		(0x00, 0x00, 0x00, 0x00),
		(0x01, 0x00, 0x00, 0x00),
		(0x02, 0x00, 0x00, 0x00),
		(0x04, 0x00, 0x00, 0x00),
		(0x08, 0x00, 0x00, 0x00),
		(0x10, 0x00, 0x00, 0x00),
		(0x20, 0x00, 0x00, 0x00),
		(0x40, 0x00, 0x00, 0x00),
		(0x80, 0x00, 0x00, 0x00),
		(0x1b, 0x00, 0x00, 0x00),
		(0x36, 0x00, 0x00, 0x00) 
	); 

	for (my $i=$Nk; $i<($Nb*($Nr+1)); $i++) {
		$w[$i] = ();#array
		for(my $i2=0; $i2<4; $i2++){
			$w[$i][$i2] = 0;
		}

		for (my $t=0; $t<4; $t++){
			$temp[$t] = $w[$i-1][$t];
		}

		if($i % $Nk == 0){
			my $temp1 = rotWord(\@temp);
			my @temp1 = @$temp1;
			#print Dumper([@temp1]) . "\n";
			my $temp2 = subWord(\@temp1);
			@temp = @$temp2;
			#print Dumper([@temp]) . "\n";
			for (my $t=0; $t<4; $t++){
				$temp[$t] ^= $rCon[$i/$Nk][$t];#whats wrong? #Use of uninitialized value in bitwise xor (^) at aes.pl line 279.
				#print $temp[$t] . "\n";
			}
		}elsif($Nk > 6 && $i%$Nk == 4) {
			my $temp2 = subWord(\@temp);
			@temp = @$temp2;
		}
		for (my $t=0; $t<4; $t++){
			$w[$i][$t] = $w[$i-$Nk][$t] ^ $temp[$t];
		}
	}
	#print Dumper ([ @w ]) . "\n";
	#exit;

	return \@w;
}

sub subWord {    # apply SBox to 4-byte word w
	my($w) = @_;
	my @w = @$w;

	my @sBox = (
		0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,
		0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,
		0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,
		0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,
		0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,
		0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,
		0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,
		0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,
		0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,
		0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,
		0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,
		0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,
		0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,
		0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,
		0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,
		0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16
	);

	for(my $i=0; $i<4; $i++){
		$w[$i] = $sBox[$w[$i]];
	}
	return \@w;
}

sub rotWord {    # rotate 4-byte word w left by one byte
	my($w) = @_;
	my @w = @$w;
	my $tmp = $w[0];
	for(my $i=0; $i<3; $i++){
		$w[$i] = $w[$i+1];
		#print $w[$i] . "\n";
	}
	$w[3] = $tmp;
	#print "test1: ".$tmp . "\n";
	return \@w;
}

# 
# Decrypt a text encrypted by AES in counter mode of operation
#
# @param ciphertext source text to be decrypted
# @param password   the password to use to generate a key
# @param nBits      number of bits to be used in the key (128, 192, or 256)
# @return           decrypted text
#
sub decrypt {
	my($ciphertext, $password, $nBits) = @_;
	my $blockSize = 16;  # block size fixed at 16 bytes / 128 bits (Nb=4) for AES
	if (!($nBits==128 || $nBits==192 || $nBits==256)){
		return '';  # standard allows 128/192/256 bit keys
	}
	my $ciphertext = decode_base64($ciphertext);

	# use AES to encrypt password (mirroring encrypt routine)
	my $nBytes = $nBits/8;  # no bytes in key
	my @pwBytes = ();#array
	for (my $i=0; $i<$nBytes; $i++){
		if($i>=length($password)){
			$pwBytes[$i] = 0;
		}else{
			$pwBytes[$i] = ord(substr($password,$i,1));
		}
	}

	my $keyback = keyExpansion(\@pwBytes);
	@keyback = @$keyback;

	$key = cipher(\@pwBytes, \@keyback);
	@key = @$key;
	$key = (@key, ($key[0..$nBytes-16]));  # expand key to 16/24/32 bytes long
	@key = @$key;

	# recover nonce from 1st element of ciphertext
	my @counterBlock = ();#array
	$ctrTxt = substr($ciphertext, 0, 8);
	for ($i=0; $i<8; $i++){
		$counterBlock[$i] = ord(substr($ctrTxt,$i,1));
	}

	# generate key schedule
	my $keySchedule = keyExpansion(\@key);
	my @keySchedule = @$keySchedule;

	# separate ciphertext into blocks (skipping past initial 8 bytes)
	my $nBlocks = ceil((length($ciphertext)-8) / $blockSize);
	my @ct = ();#array
	for ($b=0; $b<$nBlocks; $b++){
		$ct[$b] = substr($ciphertext, 8+$b*$blockSize, 16);
	}
	$ciphertext = $ct;  # ciphertext is now array of block-length strings

	# plaintext will get generated block-by-block into array of block-length strings
	my @plaintxt = ();#array

	for (my $b=0; $b<$nBlocks; $b++) {
		# set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)
		for (my $c=0; $c<4; $c++){
			$counterBlock[15-$c] = urs($b, $c*8) & 0xff;
		}
		for (my $c=0; $c<4; $c++){
			#ERROR! WTF? => Integer overflow in hexadecimal number
			$counterBlock[15-$c-4] = urs(($b+1)/0x100000000-1, $c*8) & 0xff;
		}
		$cipherCntr = cipher(\@counterBlock, \@keySchedule);  # encrypt counter block
		@cipherCntr = @$cipherCntr;

		my @plaintxtByte = ();#array
		for (my $i=0; $i<length($ciphertext[$b]); $i++) {
			# -- xor plaintext with ciphered counter byte-by-byte --
			$plaintxtByte[$i] = $cipherCntr[$i] ^ ord(substr($ciphertext[$b],$i,1));
			$plaintxtByte[$i] = chr($plaintxtByte[$i]);
		}
		$plaintxt[$b] = join('', $plaintxtByte); #php implode
	}
	  
	# join array of blocks into single plaintext string
	$plaintext = join('',$plaintxt);#php implode
	return $plaintext;
}

#
# Unsigned right shift function, since PHP has neither >>> operator nor unsigned ints
#
# @param a  number to be shifted (32-bit integer)
# @param b  number of bits to shift a to the right (0..31)
# @return   a right-shifted and zero-filled by b bits
#
sub urs {
	my($xa, $b) = @_;
	$xa &= 0xffffffff; $b &= 0x1f;  # (bounds check)
	if ($xa&0x80000000 && $b>0) {   # if left-most bit set
		$xa = ($xa>>1) & 0x7fffffff;   #   right-shift one bit & clear left-most bit
		$xa = $xa >> ($b-1);           #   remaining right-shifts
	}else{                       # otherwise
		$xa = ($xa>>$b);               #   use normal right-shift
	}
	return $xa;
}

1;