Deletable Data, and Secure uses for Structured Data

Features
102

Depends on what you mean with metadata. SAFE metadata, sure, but metadata in a file header for example, nope.

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103

I though about the creation date, modified date, things like that. It’s not in the file itself in a true file system. It’s on the directory data or somewhere else.

104

Shouldn’t get uploaded as far as I know. If you open a file with a hex editor, then any bit you change there will change at least some of the chunks of the file. If you insert or remove bytes then all chunks will come out different.

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105

Yeah, I was thinking about that. if chunk 0 is modified, the hash change and the next chunk will get modifier but only after encryption. But the hash on the second chunk stay the same so the third one and so on doesn’t change.

That is what I understand so far.

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106

Thinking again about it. I need some clarification. There is a multiple way that can be handled I think. Example is a database that increase in size over time. 3 chunks minimum I understand they all 3 changes until they reach 1 MB, after that do you really do a 3.5MB / 3 or 1MB x 3 + 0.5MB. I think the last one will be a lot more preferable to prevent that all chunks will get changed in case of append to the file.

Another thing is a client can do too is using a kind of comparer and optimize the change in the chunk but it’s not really a scenario that is going to happen often. Like keeping all the chunks size at 0.5MB and then when we add or remove some data the middle of the file then the chunk in the middle is resized and the other chunks don’t get modified (except of course the one that follow it).

I guess it’s always the client that manage the chunks so it can be improved in the future without affecting the network. And we would be able to have different kind of optimization for our need depending if it’s a database or a document that we edit often.

107

For hashing a SHA hash is used. It’s a digital fingerprint of the piece. And it’s very unique, so when you change 1 bit in a file, the hash will already change. So when I have a file (say a 10MB. movie) that get’s chopped into 10 differenty pieces with all unique hashes. When you have a different file with 10MB. (say a .rar with some pictures) the change is almost zero that our files will have the same hash.

108

You can read the Self Encryption thread or, better, the original self authentication paper (PDF) - MaidSafe.