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visits member for 2 years, 11 months
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Jun
6
comment How can I split a message in parts of similar size or smaller?
Yes, your scheme is a pretty clever way to reduce the size.
Jun
6
comment How can I split a message in parts of similar size or smaller?
+1 for a working 3-of-3 approach. I'm pretty sure tha 2-of-3 (or X-of-Y) threshold schemes require longer messages; one approach is the very similar ssss and SecretSplitter.
Jun
4
comment Encrypt-then-MAC paradigm
The answers to Should we MAC-then-encrypt or encrypt-then-MAC? discuss the security properties of Encypt-then-MAC and compare them to MAC-then-encrypt and MAC-and-encrypt.
Jun
3
comment Encrypt user email but be able to find user by email
+1 Looks good. For some applications, if the attacker already has an email address on his list, then he can already send spam to that address -- it doesn't hurt anyone if that attacker can confirm that you have the same address on your list (or not). So for those applications, non-keyed hash functions are adequate. See suppression list and Store hashed email and compare hash values.
May
25
comment How random are commercial TRNGS
By "radio", are you perhaps referring to hardware random number generators based on radioactive decay, such as hotbits ?
May
16
comment Are picture files “random enough” to be usable as a one-time pad?
@PaĆ­loEbermann: Yes, Lavarand shows that, with (a) photographs that have adequate randomness, and (b) a good randomness extractor, one can produce excellent truly random numbers.
May
16
comment True random numbers generated by sensors
Many people seem to think we should "not harvest the bits generated when it's not moving", or "only use the bottom 8 bits from some samples", or "xor together" data from various sources and only put the single final result into the entropy pool. However, the top answer from "use all and hash, or trim least significant bits?" recommends feeding all directly directly into the CSPRNG, and let the CSPRNG handle any "hashing" or "XORing" that needs to be done.
May
5
comment Theoretical pi-based stream cipher
Good point. Some numbers do have more "1"s than "9"s in its decimal representation, even if that number is normal. But I was under the impression that most mathemeticians believe that not only is pi normal, but also that the decimal representation of pi has (as far as we know) exactly the same number of "1"s, "2"s, "9"s, etc. -- see "Frequency of Each Digit of Pi" by Eve Andersson. What evidence is there that the distribution is distinguishable from random?
Apr
25
comment Theoretical pi-based stream cipher
@Thomas: "most certainly"? Many mathematicians would be very surprised if it turns out that pi is not a "normal number". Are you really saying "I have discovered a truly remarkable proof of this theorem which this margin is too small to contain."?
Feb
23
comment Algorithm/Technique for Steganography
Some of the steganography schemes listed at crypto.stackexchange.com/questions/6058/… are more efficient, in the sense of requiring a smaller file to send the same number of ciphertext bits.
Feb
1
comment Any efficient text-based steganographic schemes?
@Mok-KongShen: Yes, the warden can easily detect trailing whitespace -- but often trailing whitespace accidentally and innocently ends up in files I write and others as well. How can a warden detect a real covert channel without getting false positives from such innocent accidental whitespace? If the warden cannot distinguish innocent random whitespace from a real covert channel, then the steganographic channel is secure IMHO.
Dec
9
comment Public key cryptography - public key encrypts and cannot decrypt?
+1 nice explanation. ArtOfTheProblem uses a similar but possibly easier-to-understand explanation in their "Public Key Cryptography: RSA Encryption Algorithm" youtube video.
Dec
1
comment Software implementation of a commutative cipher?
Number of intersections of two sets gives some interesting algorithms that apparently can tell you if you have any SSNs in common, and if so, how many, without leaking any more information.
Nov
13
comment Stretching passwords for encrypting small files
+1 for linking to a complete interoperable best-practice standard for encrypting files -- OpenPGP -- rather than mentioning one particular primitive or another, which all too often are used incorrectly or at least in unnecessarily incompatible ways.
Nov
2
comment Is there a symmetric-key cryptography based on key establishment techniques?
@D.W. : Yes, Wikipedia's Kerberos protocol article lists a few RFCs that explain the protocol. I wish someone would edit Simple Wikipedia's Kerberos protocol article to explain it in a way that normal humans could understand.
Nov
2
comment Would this simple encrypted chat program be feasible using One Time Pads?
Yes, the Linux version of /dev/random is the easiest way to do true random number generation. Many hardware random number generators come with a device driver that pulls the random bits from the device, checks every block of samples, and (if it passes the checks) feeds that random data into /dev/random . If your code uses /dev/random , it automatically uses whatever HRNGs are available -- including keyboard events and mouse events.
Oct
17
comment Is there a public key semantically secure cryptosystem for which one can prove in zero knowledge the equivalence of two plaintexts?
@RickyDemer: I'm no poker expert, but I don't follow. If Alice wants to prove that message A (the ace of hearts with a freshly-generated 256-bit random number) is the same as message B (also the ace of hearts with the same 256-bit random number), can't she simply point out that X and Y are identical, without revealing the 256-bit random number or her private key or the fact that A represents the ace of hearts?
Oct
2
comment Tips on conceiving safe software messaging platform
This answer would be more useful if you named specific systems that met those needs. Are you perhaps thinking of Freenet, or what?
Oct
2
comment Salting when encrypting?
"Is there a standard for OpenSSL-interoperable AES encryption?" implies that salted encryption (or at least salted AES encryption) is common.
Oct
2
comment Is there a standard for OpenSSL-interoperable AES encryption?
related: "Salting when encrypting?"