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"A node token ("magic cookie") grants access to a subtree of the issuing user's filesystem. An associated symmetric key is required to decrypt and/or store decr

"A node token ("magic cookie") grants access to a subtree of the issuing user's filesystem. An associated symmetric key is required to decrypt and/or store decryptable data." https://mega.co.nz/#developers https://mega.co.nz/#developers Apparently, they use unsalted symmetric key encryption which allows them to discover [hash(file), password] duplicates. By comparison, the old Megaupload would apparently deduplicate based on [hash(file)] matches. Suppose Alice and Bob have files [D, E, F] and [F, G, H], respectively. If MEGA discovers that Alice and Bob share a duplicate file F and Alice to reveals her password (through password frequency analysis or to the Government), then all of Bob's files are compromised. I would personally feel unsafe storing private documents on Mega due to the lack of public/private key encryption, but that's me.

jiggy2011 14y ago
I'm not entirely sure what they mean by a "magic cookie" here. The document does say it uses public/private keys for data transfer. You would not usually use public/private for data storage because of the huge keysizes required.
- politician 14y ago
  I think the cookie bit is just an authorization credential. If they use asymmetric encryption for data transfer, then how does that work as part of a convergent encryption scheme? Wouldn't all of the file hashes be different at that point?
  - jiggy2011 14y ago
    I would assume the asymmetric crypto is just for the transfer. In other words you encrypt the data and then send it wrapped in another layer of public/private crypto. Not entirely sure though.
jlgreco 14y ago
> I would personally feel unsafe storing private documents on Mega due to the lack of public/private key encryption, but that's me. It is probably worth pointing out that all of this encryption stuff is only for them. Nomatter how they brand it, the purpose is to give them plausible deniability, which they lacked with the previous Mega. If you want encryption meant for you, then you should probably just encrypt your files yourself before you let Mega touch them.
- soup10 14y ago
  It's pretty embarrassing that tech blogs are even covering this. Copyright law is about intent, not about technical specifics. The idea that new megaupload is ok because it encrypts illegitimate content before storing it is absurd.
  - jlgreco 14y ago
    What do you mean by "ok"? Morally ok? That is subject to opinion. I don't have a problem with them now, and I never did. Legally immune? They very well could be. Certainly any action against them is going to be much harder this time, if only because a bunch of people in New Zealand are still pissed about what happened last time without the revisions that were made. If their system works as they claim, and renders them unable to govern content, then how could they be considered culpable for content? If I start posting nasty stuff encrypted with PGP to HN, would HN be to blame for failing to recognize the nasty stuff and remove it?
    - jakejake 14y ago
      As soon as a file goes public and anybody can get it, then it seems to me irrelevant that its encrypted on mega servers. They'll have to respond to takedown requests because the contents are known. And if mega is de-duping content then that could technically eliminate "whack a mole" for the copyright holders (except for people re-encoding the file and re-uploading). I had heard in the past that mega would only take down one link.
      - jlgreco 14y ago
        > They'll have to respond to takedown requests because the contents are known. And presumably, unless they think they can legally get away with ignoring it, they will. What they won't be able to do is respond to a request that says "Delete all copies of [Big movie of the year], and continue to delete all of our movies as they pop back up."
        14y ago
htf 14y ago
To be fair, if there's any chance that your password is the same as someone else's, then you have a terrible password.
- rmc 14y ago
  Unfortunately for a lot of mundane (non hacker) users, this is very likely.

jiggy2011 14y ago

I'm not entirely sure what they mean by a "magic cookie" here. The document does say it uses public/private keys for data transfer. You would not usually use public/private for data storage because of the huge keysizes required.

politician 14y ago
I think the cookie bit is just an authorization credential. If they use asymmetric encryption for data transfer, then how does that work as part of a convergent encryption scheme? Wouldn't all of the file hashes be different at that point?
- jiggy2011 14y ago
  I would assume the asymmetric crypto is just for the transfer. In other words you encrypt the data and then send it wrapped in another layer of public/private crypto. Not entirely sure though.

jlgreco 14y ago

> I would personally feel unsafe storing private documents on Mega due to the lack of public/private key encryption, but that's me. It is probably worth pointing out that all of this encryption stuff is only for them. Nomatter how they brand it, the purpose is to give them plausible deniability, which they lacked with the previous Mega. If you want encryption meant for you, then you should probably just encrypt your files yourself before you let Mega touch them.

soup10 14y ago
It's pretty embarrassing that tech blogs are even covering this. Copyright law is about intent, not about technical specifics. The idea that new megaupload is ok because it encrypts illegitimate content before storing it is absurd.
- jlgreco 14y ago
  What do you mean by "ok"? Morally ok? That is subject to opinion. I don't have a problem with them now, and I never did. Legally immune? They very well could be. Certainly any action against them is going to be much harder this time, if only because a bunch of people in New Zealand are still pissed about what happened last time without the revisions that were made. If their system works as they claim, and renders them unable to govern content, then how could they be considered culpable for content? If I start posting nasty stuff encrypted with PGP to HN, would HN be to blame for failing to recognize the nasty stuff and remove it?
  - jakejake 14y ago
    As soon as a file goes public and anybody can get it, then it seems to me irrelevant that its encrypted on mega servers. They'll have to respond to takedown requests because the contents are known. And if mega is de-duping content then that could technically eliminate "whack a mole" for the copyright holders (except for people re-encoding the file and re-uploading). I had heard in the past that mega would only take down one link.
    - jlgreco 14y ago
      > They'll have to respond to takedown requests because the contents are known. And presumably, unless they think they can legally get away with ignoring it, they will. What they won't be able to do is respond to a request that says "Delete all copies of [Big movie of the year], and continue to delete all of our movies as they pop back up."
      - 14y ago

htf 14y ago

To be fair, if there's any chance that your password is the same as someone else's, then you have a terrible password.

rmc 14y ago
Unfortunately for a lot of mundane (non hacker) users, this is very likely.