Random Data/Padding when burning cd/dvds

[andymcgill]

Hi,

When burning cd/dvds day in nero is any random data/padding stored to the disc and if so where does it come from.

Is it just zeros or random numbers or is it random bytes pulled from the ram or the hdd.

Many Thanks

[chuckskull]

No, the data required is burned and then the disc is finalised(a bit of code that tells the drive that's the end of the data). The rest will be left blank.

You can see this on discs with small amounts of data, hold it up to the light you'll see where the disc has been written to in the centre and the unused space around the edge. You can't go back and fill the empty space once a disc has been finalised, unless you're using re-writeable discs.

[andymcgill]

Thanks for the reply.

When I burn a very small amount of data to a dvd there seems a large amount of written data is relation to the file burned. Is this just the leadout.

[Splash]

The leadout is pretty small potatoes in the grand scheme of things. Can you quantify this "large amount"?

[watercooled]

You mean based on time? If so that's pretty normal, I'm not certain why but I think the leadout might be written at a lower speed or something.

[Donni10]

It may be the CD/DVD's your trying to use?

[andymcgill]

No I'm talking about the amount of data on the disk (2MB File) compared to the amount of burned data on the dvd.

I'm basically wanting to know what gets written to the cd/dvd that isn't the data you are writing to it. Is there any sort of padding to bulk out the cd/dvd if the amount being burned is small or padding in the cluster tips, and if so is this data just randomly generated bits or is it random bits pulled from the ram/filesystem


Thanks

[watercooled]

What is telling you the amount of data on the disc, My Computer?
Anything that uses padding would use either null characters or random bits, using data pulled from RAM/filesystem would be a huge security concern.

[andymcgill]

Thanks for the replies.

It was in the first reply that you can seen the amount of data burned by looking physically at the disc where you can see the data physically burned.

When doing this with a disk with a very small data written I commented that the burned area physically looked a lot bigger than I thought it should for the data.

I'm basically trying to find out if any data other than the data you gave in your session burned to the disc and if so where the data comes from.

I'm aware that there is data written and the start and at the end. I was trying to find out whether this contained random data and if so whether this was drawn from hdd or ram.

I was wondering because files on a hard disk have cluster tips. I read that old versions of windows wrote random bytes from ram to fill the cluster tips. I was wondering whether burned cds have cluster tips, what is stored in them if they do and whether any other sort random written and if so where does this data come from.

I have looked on the web but I can't see any relevant info.

Thanks

[peterb]

Are you referring to slack spavce where the file length is less than the cluster size? (when the remainder of the cluster may contain data from a previous file?)

AFAIK, the CD is only written with the data - it does contain a directory structure, but if the disk is blank, then remaining cluster space would be blank. A lot of the finalising is writing the drectory structure to the CD, but the process depends on the CD standards employed.

The most common (and simplest) is ISO 9660.

There is some information here although for a definitive answer you should go to the surce documents, particulary if your question is related to data security.