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Jul
18
comment How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
Am I correct in assuming the implementation I linked is closer to a stream cipher? en.wikipedia.org/wiki/Stream_cipher (couldn't edit my last one, was past 5 min :/ )
Jul
18
awarded  Commentator
Jul
18
comment How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
What would the proper terminology for it be? And how weak would it be? As I said in my main post, I'm not extremely experienced with all of this, I mostly wrote that to experiment with stuff and see what I could do. It's not exactly a pad, no, but I'm not intending to use it as full on encryption either. Also, would you mind commenting on the strength of that implementation? Thanks.
Jul
18
comment How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
Also still not sure what is implemented in that link is really a one-time pad. It's unique for the file, and the 192-byte blocks inside of it, but it's not completely random, though the third key changes with each file, and each block gets it's own unique key due to the block number (I can't make it random without storing a -ton- of data)
Jul
18
accepted How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
Jul
18
comment How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
This is actually closer to the kind of insight I was looking for with it. While it wouldn't be breakable, it would be more difficult in cases where AES was sufficiently weakened. Also in the example AES is applied first. I was merely intending to use this as a pad over AES. I actually came up with a new method for padding the AES which involves 3 keys and a block number. It's essentially a one-time pad for each file, that gives each 192-byte block it's own unique xor key/cipher. I made a rough implementation of it here: pastie.org/private/qjghdungunlbs64qakdgva# (C#)
Jul
18
awarded  Scholar
Jul
17
comment How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
That's true, in which case my previous (second) comment would be rendered moot as they could then use those 100 files to essentially guess between the layer of AES.
Jul
17
comment How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
Also should be noted I'm not interested in implementing this, and will more than likely just add another layer of security if I went that route (I trust AES so I don't really think it's a huge issue), but the way I see it still is even if they were able to get 100 of the files that were represented in the encrypted files as well (Through finding them on the drive, not decryption), it still wouldn't really help them break the XOR pad since there's still a layer of AES separating it. Or am I looking at that wrong? Thanks for the answer, as well!
Jul
17
comment How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
This makes a good point, using a second encryption scheme which is a strong contender with AES would make sense to increase security significantly as opposed to re-inventing the wheel (or at least making my own "wheel"). Would +1 but can't due to rep. However, the linked post isn't quite accurate to the situation. They all deal with educated guessing or suspecting common phrases in the unencrypted text, where as I am encrypting something then performing a two+ pad on it. The underlying bits wouldn't really be "guessable" as far as I know? Still a good read, though.
Jul
17
revised How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
Added some further clarification after reading two referenced crypto.stack questions. Also replaced the word "cipher" with "key" because that's more accurate.
Jul
17
comment How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
@e-sushi I read through those two posts, and am adding some more clarification. They were an interesting read as well, ty!
Jul
17
revised How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
Removed occurrences of "one time pad" and made it just "pad", as pointed out this isn't a one time pad.
Jul
17
comment How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
@fgrieu Added some clarification. I know it invalidates it as a "one time" pad, though I don't really know what else to call this process. I guess just a pad? Thanks.
Jul
17
revised How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
added 106 characters in body
Jul
17
comment How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
@e-sushi Thanks for the references, I'll have a look at those as well!
Jul
17
comment How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
@e-sushi That's true, though one aspect of what I was wondering is if the fact that the only thing it's repeatedly used on is binary (AES encrypted) output, does that pose as much risk? Every time I hear it mentioned it's always under the context of no previous encryption used, but rather just on some plain text file. Also thanks for the comment! And np on the time. Edit: It's not that I doubt the security of AES, but rather a curiosity question about the use of xor with a repeated key/cipher in this context as opposed to what it's usually brought up in.
Jul
17
revised How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
Fixed wording.
Jul
17
awarded  Editor
Jul
17
revised How secure is using a pad (using xor) on a encrypted data, for the purpose of obfuscating/hiding the underlying encryption?
Fixed a grammar thing that was driving me nuts.