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seen Nov 13 at 16:01

Sep
29
comment Cryptographic data structure: sparse array without membership test
If the person writing data could keep track of exactly what key,value pairs he has written so far (in some in-RAM structure that the attacker, and hence the reader, won't have access to once the computer is shut down), then perhaps the surprising-to-me dirty paper coding approach could be used -- rather than "most recent value wins" every collision, sometimes "let the older value win this collision" is better when there is enough error correction that the new value can still be recovered from other, non-colliding bits.
Sep
29
comment Cryptographic data structure: sparse array without membership test
+1. And thank you for making "Is deniable error-correction possible?" a separate question.
Sep
29
comment Cryptographic data structure: sparse array without membership test
@gmr: yes, very similar to your solution, except this proposal doesn't require decrypting the 'k' value and checking if the decrypted 'k' value matches the current 'k' value. So this proposal apparently runs a little faster.
Sep
27
comment Cryptographic data structure: sparse array without membership test
This sounds distantly related to multiple-message encoding in steganography. Alice carefully constructs an image that appears to be an innocent cat photo, but embeds multiple messages inside such that Oscar can extract one message from Alice, Trent can extract another message from Alice, but Oscar and Trent (assuming they don't collaborate) can't even detect that any other message exists in the image. Can one of the multiple-message encoding techniques be adapted to solve this problem?
Sep
24
comment Understanding Pseudo Random Generators
@TravisMayberry: Would you mind telling me what "n" is for RC4/CipherSaber, Salsa20, or some other real PRNG implementation? Or are you pointing out a difference between the theoretical definition, and what I see in practice?
Sep
21
comment Single-purpose symmetric encryption scheme for single files
For the "file" command to work properly, you're going to want the first few bytes of the file to describe what kind of file this is -- often the the name of the program that produces the file (in UTF8 characters), followed by a version number.
Sep
21
comment Single-purpose symmetric encryption scheme for single files
What is the advantage over " 7z a -p outfile infile.txt "? (Perhaps using 'tar', as described in the 7z man page, to store the metadata). See "7-Zip's AES encryption".
Sep
2
comment Repeatable crypto
Yes, a system that lets the attacker get the encryption key -- is broken. However, there is a way to attack the deduplication, even if the attacker doesn't know the original key.
Aug
29
comment What is the most secure hand cipher?
@AaronToponce: by "this", do you mean the cipher is impractical, or that the cipher is practically secure against this attack because this particular attack is impractical?
Jul
29
comment Is there a cryptographic hash function that can be performed with pencil and paper?
@JohnDeters: I agree that colluding web site admins is unrealistic. However, I have accounts on so many different websites that it is not unreasonable to suspect that at least 2 of those sites will accidentally leak my password to an attacker.
Jun
11
comment Can you help me understand what a cryptographic “salt” is?
@Mike: Who? Someone says "You should always assume the attacker knows the salt.". People at another page says "Salts are public", and later says "the salts are known, because that's the industry-standard use of the word salt." Another says "the salt are public knowledge, or at least should be treated as public knowledge.".
Apr
21
comment encrypt message with one digest 0-9 instead of 01-26
I've been told that historically this Gronsfeld cipher was actually used more often than the Vigenère cipher.
Mar
22
comment Do any one-key-of-many cryptographic schemes exist?
+1. Perhaps you might also mention: This standard construction is standardized in more detail in "RFC 4880: OpenPGP Message Format".
Mar
15
comment Analogue encryption algorithms
I agree that most of these systems are mostly just obfuscation. Most people define things like the Playfair cipher as "encryption", although it is relatively easily distinguished from white noise. Even using your unnecessarily strict definition of "encryption", I suspect that it may be possible to build an analog system that would be practically indistinguishable from white noise; with a vocoder + frequency hopping using a "good" pseudo-random number generator + random chaff.
Mar
15
comment Analogue encryption algorithms
I dunno; I suspect that with a bit of tweaking the vocoder + frequency hopping using a "good" pseudo-random number generator + random chaff would be pretty close to indistinguishable from white noise.
Jan
24
comment Is there a standard for OpenSSL-interoperable AES encryption?
related: "Wheres the salt on the openssl aes encryption?"
Jan
24
comment Impact of distinguishing between random text and cipher text?
Wikipedia: Feistel cipher currently claims that '4 rounds are sufficient to make it a "strong" pseudorandom permutation'. Is Wikipedia wrong, or am I misunderstanding Patarin or Wikipedia or both?
Jan
13
comment Convert old and busted password encryption to something sensible
related: Increase the security of an already stored password hash
Jan
12
comment Is there a simple hash function that one can compute without a computer?
related: crypto.stackexchange.com/questions/11691/…
Jan
2
comment How does the secret key in an HMAC prevent modification of the HMAC?
@StephenTouset, by "appending data to the end", I think George is referring to a length extension attack, which is not trivial.