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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
24
answered Requiring a “supervisor” key pair and a “user” key pair to decrypt multiple-recipient messages
May
16
comment Are picture files “random enough” to be usable as a one-time pad?
@PaŭloEbermann: 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
answered Using the output of a stream cipher, how to guarantee the integrity of 4 bytes of data?
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
11
answered Name for identical operations for encryption and decryption
Feb
3
answered Store hashed email and compare hash values
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.
Feb
1
revised Any efficient text-based steganographic schemes?
add references, as requested.
Jan
29
answered Cryptographic Symmetric Stream Cipher
Jan
24
answered Any efficient text-based steganographic schemes?
Dec
16
answered Contruct a protocol to determine if three secret keys are different, without revealing any of them?
Dec
9
revised sha-1 wiki description
I hate it when people say "Don't use X", without stating some alternative.
Dec
9
suggested suggested edit on sha-1 tag wiki
Dec
9
revised Deterministic key generation
edited tags