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I thought tarsnap is completely different in that it is in a way its own cloud storage that uses S3 as the backend? As in it encrypts your files, dedups and pu
by lqdc13 10y ago
I thought tarsnap is completely different in that it is in a way its own cloud storage that uses S3 as the backend?
As in it encrypts your files, dedups and puts them on S3?
- DigitalJack 10y agoWouldn't you have to de-dupe prior to encryption? Sorry if I'm being pedantic. I would just not expect anything to deduplicate once it's encrypted.
- yorwba 10y agoWhy not? Encrypting two identical files with the same key gives you two identical encrypted files.
- diggs 10y agoHow about if a single byte changes? Now the encrypted output looks 100% unique, and you have to treat it as an entirely new file. You lose the ability to do diffs on a file by file basis or proper deduplication across all files.
- quickben 10y agoThat's defeating the purpose of encrypting them. If you don't CBC, wherever is on the cloud side will have two files with one block off. Let's assume the file is a txt file. For smaller cipher block sizes, it is becoming very easy to guess your encryption key. Tldr, you want any attacker to lose any diff ability on your encrypted data.
- diggs 10y agoThat depends on how you're storing the files. I was really just trying to highlight that for deduplication across files you need to deduplicate before you encrypt.
- Dylan16807 10y agoGuess the encryption key? That shouldn't be possible, even if you use something as terrible as ECB.
- RachelF 10y ago>two identical encrypted files. Good practice for file encryption is to pad some random bytes to the start of a file. This makes known cyphertext attacks much harder. So encrypting identical files should result in different files and also slightly different length files.