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Dec
29
comment Salts, how does the script know what the salt is?
Yes, and often the name of the hash algorithm is also concatenated to the salt and the hash, in Modular Crypt Format or LDAP / RFC2307 format.
Nov
13
comment How can we get CA's public key?
@CodesInChaos: make that an answer.
Nov
12
comment How would I make a secret notation alphabet more secure?
You might enjoy looking at shorthand systems such as Gregg shorthand -- they were never intended to be difficult to decode, but some stenographers use so many of their own custom abbreviations that even other stenographers using the same system have difficulty reading it.
Nov
12
comment Is this hand cipher any more secure than the Vigenère cipher?
You could get a lot better diffusion if, rather than handle each letter independently with "mod 26", you allow a carry over -- i.e., when adding 5 to X and obtaining C, you get a "carry over" that changes the next column from E+3=H to E+3+1=I.
Oct
23
comment What is the most secure hand cipher?
@makerofthings7: if it is used properly, as Smit Johnth pointed out, then OTP is completely immune to statistical analysis and every other kind of ciphertext-only analysis, no matter how the letters are encoded into numbers -- ASCII, Baudot code, Morse code, etc. See Wikibooks: one time pads for more details.
Oct
16
comment Any efficient text-based steganographic schemes?
This steganographic scheme is called an acrostic ( Wikipedia: acrostic ).
Aug
4
comment Why are there $ signs in my passwd file?
+1. Recently people at Wikipedia shuffled things around. Is crypt (C) on Wikipedia what this answer ought to link to?
Jul
16
comment Physical analogue for MACs
+1. To make this more analogous to a real MAC, we could assume that an attacker could steal the case (and everything inside it) and substitute a similar-looking one of his one -- only someone with the "real" key would discover that it doesn't unlock the replacement case, just as only someone with the real secret key can tell that a substituted message with a substituted MAC isn't the original message.
Jul
15
comment Physical analogue for MACs
@Reid -- you have two pretty good ideas here; I wish you had posted them as two separate answers, so that the "better one" (whichever that may be) would float to the top. +1 anyway.
Jul
13
comment Physical analogue for MACs
@PaĆ­loEbermann: Yes, that's how most MACs work -- everyone who can check the MAC can also produce their own. When teaching people about MACs, we want the physical analogue to have the same flaws as the actual MAC.
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.