I am not an encryption expert but from what I have read multiple encryptions of data are possible, and there are two ways to look at it. >From an theory/encryption standpoint there is nothing wrong with encrypting one thing in another, ie an AES-encrypted zip on a loop-aes'd drive because the file is recognized as a file by the filesystem and block driver, (I have AES-encrypted zips on a loop-aes'd drive), so in that respect it would work. I've heard that a problem might arise that if a skilled cryto-attacker looks at it, (s)he can sometimes look at patterns of one encryption "layer" to infer things about the other "layer", meaning there could be patterns found on one layer in the cipher text that make the key of the other layer more predictable, which makes the overall data structure more vulnerable - but again I am not a crypto-expert. >From a practical/implementation standpoint, I know of no product or program that attempts this. Putting encrypted files on a loop-aes drive does not count as "the same thing twice", because they are at different "system layers" (roughly OSI model). The best way to secure data is to make sure the cipher and program you use are well tested by trusted and competent people. In general encryption is hard enough to get working, and if done right, even harder to break - "double-encryption" would probably only make it harder to get working, and possibly easier to break. With that said, does anyone know of anything that will do double encryption? David Jan Luehr wrote: > Hello, > > I recently wondered if multiple encryption can decrease the security of > encrypted information. > Imho we can basically think of two different scenarios: > 1st. Encrypting information twice. > For instance: An RSA encrypted mail is stored on a loop-aes encrypted > harddrive. (If you think of XOR, you run into serious problems, if using same > keys, but I guess RSA and AES won't be a problem at all.) > > 2nd. Encrypting information more times. > For instance: Backups are done on removeable media. Each one is encrypted with > a different set of keys for loop-aes, but also containing very similar data. > > Do you know, serious studies or trust-/helpful reports, etc. on what > algorithmens / implementations can / should / mustn't be combined and how > multiple encryption effects security? > > Thanks in advance. > Keep smiling > yanosz > > - > Linux-crypto: cryptography in and on the Linux system > Archive: http://mail.nl.linux.org/linux-crypto/ > > - Linux-crypto: cryptography in and on the Linux system Archive: http://mail.nl.linux.org/linux-crypto/
