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Apr
27
comment How to use OpenSSL command line utility to encrypt data with encrypted key from public key?
I am curious: is there a reason anyone would use that specific format for anything other than educational purposes, rather than in a standard format such as PKCS12 ("openssl pkcs12 ...") or S/MIME ("openssl smime ...") or the OpenPGP format ("gpg --output doc.gpg --encrypt --recipient someone@example.org doc.txt" and decoded by "gpg --output doc_copy.txt --decrypt doc.gpg")?
Apr
8
comment What problems with “random” data would cause this result from Ent?
+1: I agree that this chi squared test is detecting certain byte values occurring more often than one expects from true random data, a pattern overlooked by other tests. Accidentally discovered a random number generator? It's possible: The bug may exercise 2 or more of each core's oscillator plus the RTC oscillator. Two hardware oscillators are a key component in many true hardware random number generators. See US5117380 A (1992); Jun and Kocher "The Intel random number generator" (1999), Baudet et. al. "On the security of oscillator-based random number generators" (2009), etc.
Apr
6
comment Are all self-synchronizing cryptosystems necessarily self-synchronizing stream ciphers?
@otus: These "self-synchronizing ciphers" you mention -- can you name even one that is not effectively a "self-synchronizing stream cipher"? I would be very interested in any such (non-stream) self-synchronizing cipher, even if it required me to know exactly where the dropped byte(s) should have been. On the other hand, perhaps no such cipher is possible? Either way, I look forward to learning something I didn't know before.
Apr
2
comment Can error correcting codes be used to guess this plaintext?
Case (b) reminds me of deniable encryption algorithms.
Mar
31
comment random access stream cipher
My understanding is that the XTS mode and CTR mode (and all other popular whole-disk encryption modes) does "encrypting and decrypting the same location twice, with the same key." when writing to the disk. Are you seriously saying that all of them are doing it wrong?
Mar
31
comment A self-decrypting block-cipher
This reciprocal cipher reminds me a lot of the (usually not reciprocal) "single-key Even-Mansour cipher".
Mar
21
comment Is regular CTR mode vulnerable to any attacks?
The "CTR", as described in the Wikipedia: block cipher mode of operation article, is a mode of operation that is used with a block cipher, often AES. That CTR is not a cipher in itself. Are you maybe referring to some other CTR? Which one?
Mar
20
comment Is regular CTR mode vulnerable to any attacks?
I don't know of any way to use AES without also using some block cipher mode of operation. AES256 is often used with CTR. So your question doesn't make sense to me, it's like asking "Which is better, a truck with a diesel engine or a truck with 4 wheels?", when most trucks have both. Did you maybe mean to ask "Which is better, XTS or CTR to encrypt a drive?"?
Feb
23
comment Why does rsyncrypto require a public key during decryption?
@MaartenBodewes: While "Don't use security protocols that aren't even well described" is, in general, good advice, I don't see how it is relevant to this question about rsyncrypto, which is fairly well described on the Rsyncrypto Algorithm page.
Feb
23
comment How to make a “zero knowledge” cache/key-value store
When I derive a key from the password, I prefer to use a key-derivation function (KDF) rather than a HMAC.
Feb
23
comment How to make a “zero knowledge” cache/key-value store
This sounds like it could be very useful, perhaps as part of an InterPlanetary File System (IPFS). I look forward to good answers.
Feb
12
comment Is there a standardized tree hash?
Related: "Optimal Parameter Selection for Efficient Memory Integrity Verification Using Merkle Hash Trees".
Jan
13
comment Simplied DES why 10-bit key?
Mark, are you maybe referring to one of the simplified variants of DES mentioned at en.wikipedia.org/wiki/Data_Encryption_Standard#Simplified_DES ?
Oct
29
comment Coin flipping with limited communication between participants
@Victor: You are right. As often happens to all programmers, I have a first part of something that solves part of the problem, and then I add a second part that solves the rest of the problem; and later I realize that this second part can be used to solve the entire problem and I don't need the first part any more.
Jun
6
comment Is the one-time-pad a secure system according to modern definitions?
@CodesInChaos: I realize the original title "Has the one-time pad been broken?" was a little provocative, but I think "Does the one-time-pad meet modern security definitions?" is ambiguous. The answer is either trivially "no" (a OTP doesn't do or meet anything; people and machines do things and meet people) or trivially yes (The modern definition of a OTP has critical details not present in early cryptography definitions, and of course a real OTP matches that definition, even though other things that people might mistakenly call a OTP do not). Feel free to tweak the title further.
Mar
28
comment Are there any simple and yet secure encryption algorithms?
@archie: Did you maybe mean to link to the Simeck tweet on p. 23 of "Revisiting Counter Mode to Repair Galois/Counter Mode and Simeck: An Authenticated Cipher Design"?
Mar
28
comment Are there any simple and yet secure encryption algorithms?
@archie: Did you maybe mean to say that the SPECK128 cipher fits in one tweet ?
Dec
21
comment Any efficient text-based steganographic schemes?
Related: "Steganography to hide text within text"
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.