#!/usr/bin/perl

use strict;
use warnings;
use Digest::CRC;

my $crc = qq(f0b8);

print qq(target crc =$crc\n);

my $msg = qq(8792ebfe26cc130030c20011c89f23c8);

$msg = pack( 'H32', $msg );

my $ctx = Digest::CRC->new(width=>16, init=>0xffff, xorout=>0xffff,
               refout=>0, poly=>0x8408, refin=>1, cont=>1);

$ctx->add($msg);
my $crc2 = $ctx->hexdigest;

print qq(       crc = $crc2\n);

##</code><code>##


#!/usr/bin/perl 
use strict;
use warnings;

# https://github.com/Yubico/yubico-c/blob/master/test-vectors.txt
# https://github.com/Yubico/yubico-c/blob/master/ykcrc.c
# (yubikey_crc16)

my $plaintext = qq(8792ebfe26cc130030c20011c89f23c8);

print qq(p=$plaintext\n);

my $crc = &yubi_crc($plaintext, 16);

print qq(yubi crc = ),$crc,qq( "),sprintf("0x%02x", $crc),qq("\n);
print qq(target   = 61624 "0xf0b8"\n);

exit ( 0 );

sub yubi_crc {

    my ( $otp, $size ) = ( @_ );

    my $crc = 0xffff;   #
    
    while ( $size-- ) {

        my $byte = hex( substr( $otp, 0, 2, '' ) );

        $crc = $crc ^ ( $byte & 0xff );

        for ( my $i = 0; $i < 8; $i++) {
            my $n = $crc & 1;
            $crc = $crc >> 1;
            $crc = $crc ^ 0x8408 if ( $n != 0 );
        }
    }
    return ( $crc );
}