XnView Software

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# Encrypt or decrypt Pentax ShutterCount (symmetrical encryption) - PH
# Inputs: 0) shutter count value, 1) ExifTool object ref
# Returns: Encrypted or decrypted ShutterCount
sub CryptShutterCount($$)
{
    my ($val, $exifTool) = @_;
    # Pentax Date and Time values are used in the encryption
    return undef unless $$exifTool{PentaxDate} and $$exifTool{PentaxTime} and
        length($$exifTool{PentaxDate})==4 and length($$exifTool{PentaxTime})>=3;
    # get Date and Time as integers (after padding Time with a null byte)
    my $date = unpack('N', $$exifTool{PentaxDate});
    my $time = unpack('N', $$exifTool{PentaxTime} . "\0");
    return $val ^ $date ^ (0xffffffff - $time);
}