#!/usr/lib/perl 

use Time::HiRes qw(gettimeofday);	# Get time in microsec and sec precision
use Crypt::Ctr;				# Usage of Crypt in Counter Mode

print "\nPlease input the key for Counter Mode operation: ";
$key = <stdin>;
print "Please input the Plaintext for Counter Mode operation: ";
$p_text = <stdin>;
print "Please input the Ciphertext for Counter Mode operation: ";
$c_text = <stdin>;
print "Please input the Recovered Plaintext for Counter Mode operation: ";
$r_text = <stdin>;

########################################
# 1. a) Open input file
#    b) Append to array @plaintext
########################################

	open(PLAIN, "$p_text") or die "File does not exist: $!";
	binmode PLAIN;
	while(<PLAIN>){
	  @plaintext[$element_a] = $_;
	  $element_a++;
	}
	close PLAIN;

########################################
# 2. a) Start Encryption Process
#    b) Get start time (encryption)
#    c) Print Encrypting
########################################

	my ($s_a, $usec_a) = gettimeofday;

	print "\n: : : Encrypting : : :";

########################################
# 3. a) Create cipher from counter + key
#    b) Use either block-cipher or hash
########################################

        for ($i = 0; $i < @plaintext; $i++){
	        $cipher[$i] = new Crypt::Ctr $key, 'Digest::MD5';
	}

########################################
# 4. a) Encrypt plaintext -> ciphertext
#    b) Use XOr embedded Crypt::Ctr
########################################

        for ($i = 0; $i < @plaintext; $i++){
		$ciphertext[$i] = $cipher[$i]->encrypt($plaintext[$i]);
	}

########################################
# 5. a) Get stopped time (encryption)
#    b) Get interval ($time_a - time_b)
#    c) Print Finished Encrypting
########################################

	my ($s_b, $usec_b) = gettimeofday;

	my $usec_c = $usec_b - $usec_a;
	my $s_c = $s_b - $s_a;

	my $time_a = ($s_c*1000000) + $usec_c;

	print "\n: : : Encryption Finished : : :";

########################################
# 6. a) Open cipher file
#    b) Append from array @ciphertext
########################################

	open(CIPHERTEXT, ">$c_text");
	binmode CIPHERTEXT;
	foreach $e (@ciphertext){
	  print CIPHERTEXT $e;
	}
	close CIPHERTEXT;

########################################
# 7. a) Start Decryption Process
#    b) Get start time (decryption)
#    c) Print Decrypting
########################################

	my ($s_d, $usec_d) = gettimeofday;

	print "\n: : : Decrypting : : :";

########################################
# 8. a) Reset cipher
#    b) Decrypt ciphertext -> plaintext
#    c) Use XOr embedded Crypt::Ctr
########################################

        for ($i = 0; $i < @ciphertext; $i++){
		$cipher[$i]->reset;
        	$recovertext[$i] = $cipher[$i]->decrypt($ciphertext[$i]);
	}

########################################
# 9. a) Get stopped time (decryption)
#    b) Get interval ($time_a - time_b)
#    c) Print Finished Decrypting
########################################

	my ($s_e, $usec_e) = gettimeofday;

	my $usec_f = $usec_e - $usec_d;
	my $s_f = $s_e - $s_d;

	my $time_b = ($s_f*1000000) + $usec_f;

	print "\n: : : Decryption Finished : : :\n";

########################################
# 10. a) Open recovered file
#     b) Append from array @recovertext
########################################

	open(RECOVER, ">$r_text");
	binmode RECOVER;
	foreach $e (@recovertext){
	  print RECOVER $e;
	}
	close RECOVER;

########################################
# 11. a) Show input-cipher-ctext-ptext
#     b) Show time encrypt-decrypt
########################################

	#print "\nInput: \n@plaintext\n";
	#print "\nCipher: \n@cipher";
	#print "\nCiphertext: \n@ciphertext\n";
	#print "\nRecovertext: \n@recovertext\n";
	
	print "\n:::Encryption:::";
	print "\nTime started: $s_a $usec_a";
	print "\nTime finished: $s_b $usec_b";
	print "\nTime elapsed: $time_a microsec\n";

	print "\n:::Decryption:::";
	print "\nTime started: $s_d $usec_d";
	print "\nTime finished: $s_e $usec_e";
	print "\nTime elapsed: $time_b microsec\n";