package pc;
use strict;
use Digest::SHA qw(hmac_sha256 sha1 sha224 sha384);
use Exporter "import";
use vars '@EXPORT_OK';
use bytes;
sub step {
 my $i=shift;
 $_[$i->[0]]^=
    hmac_sha256(substr("op",abs($i->[0]),1)
                ,$i->[-1]
                ,$_[$i->[0]-$i->[1]].$_[$i->[0]+$i->[1]]);
 $i->[0]+=1;
 return ($i,$_[1],$_[-1],$_[0])
}
sub block{
 my ($key,$d,$s)=@_;
 return shift if @_==1;
 $key=[-1,1+-2*$d,$key]if!ref$key;
 my @r=reverse step step step $key,substr($s,0,32),substr($s,32,32),substr($s,64,32);
 pop @r;
 return join"",@r
}
sub hash{
 my $b=shift;
 return scalar reverse sha224($b).sha384($b).sha1($b)
}
sub test{my($k,$d)=@_;
return $d eq round $k,1,round $k,0,$d
}
sub size(){96}
sub encrypt{my($k,$d)=@_;
 return 1 if!@_;
 return([-1,-1,@_],1)if@_==1;
 my$o=(length$d)%size;
 my$b=hash $d;
 my$iv=$b;
 $b.=$d;
 my$r=$iv;
 my$x;
 for($x=size;$x+$o<length$b;$x+=size){
  $iv=block$iv.$k,1,substr$b,$x,size;
  $r.=$iv
 }
 $r.=substr$d,$x- size,$o;
 $b=substr$r,$o;
 my$h=block$k.$b,1,hash$b;
 my$e=substr$r,0,$o;
 $e^=substr$h,0,$o;
 $iv=block$e.$k,1,hash$k.$e;
 for($x=$o;$x<length$r;$x+=size){
  my$c=$iv.$k;
  $iv=substr$r,$x,size;
  $e.=block$c,0,$iv
 }
 return$e
}
sub decrypt{my($k,$e)=@_;
 return 0 if!@_;
 return([-1,1,@_],0)if@_==1;
 return undef if size>length$e;
 my$o=(length$e)%size;
 my$x=substr$e,0,$o;
 my$r="";
 my$iv=block$x.$k,1,hash$k.$x;
 for($x=$o;$x<length$e;$x+=size){
  $iv=block$iv.$k,1,substr$e,$x,size;
  $r.=$iv
 }
 my$h=block$k.$r,1,hash$r;
 my$b=substr$e,0,$o;
 $b^=substr$h,0,$o;
 my$d="";
 $b.=$r;
 $e=$iv=substr$b,0,size;
 for($x=size;$x+$o<length$b;$x+=size){
  my$c=$iv.$k;
  $iv=substr$b,$x,size;
  $d.=block$c,0,$iv
 }
 $d.=substr$b,-$o,$o;
 return undef if $e ne hash $d;
 return $d;
}
@EXPORT_OK=qw(encrypt decrypt block size hash);