Firstly, since identical files will always produce the same cipher data, a person with that exact original file could encrypt it and then identify instances of that file on Bitcasa’s severs. There are two important weaknesses to convergent encryption. Since Bitcasa doesn’t have the original file, they don’t have the key, and the data is safe - mostly. When those bits of data hit the Bitcasa cloud servers, it's a trivial process to find matching files and remove the duplicates. So the two individuals above would encrypt their data, and as long as the files are identical, the resulting encrypted files would be identical. In convergent encryption, the file being encrypted is used to derive the key. Since it would be spectacularly insecure to give all users identical keys for all their encryption needs, it has to go back to what the users already have in common: the file itself. The only way for Bitcasa to do it’s magic is for the output of encryption, sometimes called the cipher data, to be the same for all copies of a particular file.
Since the two privately encrypted files wouldn’t be the same anymore, Bitcasa would have no way to match them for de-duping. The resulting files are unreadable without the individual private keys, and more importantly, they look like different files at the end. This scenario is basically traditional encryption, and wouldn’t do Bitcasa any good. Imagine that two people have an identical file and each one of them uses a private key to encrypt it.
To understand those risks, it’s important to understand how convergent encryption is unique. Well, after plenty of speculation, the company has expanded on their initial statements saying that the combo of de-duping and encryption is made possible by convergent encryption.Ĭonvergent encryption solves the problems cited with Bitcasa, but does present some risks. The issue many users pointed to is that Bitcasa will encrypt files on the client side, so how can a file be de-duped on Bitcasa’s servers? Presumably, they wouldn't be able to tell what the file is, and sharing the encryption key with Bitcasa would defeat the purpose. The key to this, the CEO explained at the Disrupt conference, was a special de-duplication algorithm that would remove duplicate data from multiple users, thus reducing total storage needed on the server side.
Silicon Valley start-up Bitcasa made some waves last week when they claimed their upcoming cloud storage service would provide unlimited storage for just $10 per month.
0 kommentar(er)
