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Mar
27
comment Why is CRC said to be linear?
Setting $c=0$ in the alternate equation might be a useful exercise: $crc(a) \oplus crc(b) \oplus crc(0) = crc(a \oplus b)$. Then, one naturally questions what $crc(0)$ evaluates to, tying into your point about starting at a nonzero state.
Feb
25
comment What does the comma mean in m, c := E(K, m)
Well, it's really from multiple perspectives... The first is just that the := symbol typically means "defined as", so it's good to use the same language as everyone else. The second is a little vaguer: In my experience teaching, a frequent source of student confusion is the difference between "derived"/"obtained" objects versus arbitrarily-named objects. Saying "c is defined as..." just highlights that we're calling this thing c, not that we did something special to arrive at a value for c.
Feb
25
comment What does the comma mean in m, c := E(K, m)
Probably better to say 'defined as' instead of 'equals'. At least, for pedagogical purposes.
Jan
17
comment Are there any advantages in using proprietary encryption?
@DewiMorgan: This thread is about encryption, not hash functions. Besides, a concatenated "pepper" is better implemented with a real cryptographic construction, whether that's a MAC construction for a hash function (i.e. HMAC), encrypting password digests before storage, or (in newer password hash function designs) using the "pepper" as a server-side secret parameter (if available, e.g. Argon2's $K$ parameter).
Jun
11
comment Physical entropy source: How many bits entropy per byte is sufficent?
@curiosity: That's correct! As I linked above, there is a case where a malicious, privileged data source can actually decrease the security of a RNG when mixed into it, but this is essentially an edge case.
Jun
9
comment Physical entropy source: How many bits entropy per byte is sufficent?
@curiosity: For example, I just ran ent on a JPEG photo of me at a party. Result was Entropy = 7.970617 bits per byte but I can assure you that the picture is a far from being near truly random.
Jun
8
comment Physical entropy source: How many bits entropy per byte is sufficent?
@curiosity: Passing ent is a necessary but not sufficient condition for a random stream. If your stream fails ent, it (with overwhelming probability) isn't truly random. If your stream passes ent, it may or may not be truly random - but ent cannot determine which. It is a tool that is only useful as a negative indicator.
May
20
comment Can i get a list of over hard and long RSA keys? i think i have found a vulnerability in RSA Algorithm
Ah, yeah, RSA-2048 would have been a better choice in retrospect. Truth be told, I just completely forgot about it.
May
20
comment Can i get a list of over hard and long RSA keys? i think i have found a vulnerability in RSA Algorithm
I think this question uniquely qualifies for the "too broad" close reason: there are (literally) an infinite number of possible answers.
May
20
comment Can i get a list of over hard and long RSA keys? i think i have found a vulnerability in RSA Algorithm
@user3651521: Yes. That is $n=pq$ where $p,q$ are distinct primes roughly 1024 bits in size.
May
8
comment If someone had a list of all primes, would it be possible for them to factor any integer in polynomial time?
I think this answer probably answers your question (with a little thought).
May
5
comment How to calculate if probability is negligible or not
This treatment is a little strange: I think using an asymptotic definition for negligible probabilities would lead to a more precise discussion.
May
3
comment Simplicity and precision in cryptography papers
@cpast: Your comments serves nicely as an answer.
Apr
7
comment How to decrypt a '.enc' file that has been encrypted with RSA using a public key?
You shouldn't destructively edit your posts like that. These questions are meant to serve as potentially useful references for other users. If you remove all details from your question, you destroy any existing content these future users might need.
Apr
5
comment How to decrypt a '.enc' file that has been encrypted with RSA using a public key?
You cannot decrypt the file without the private key. Therefore, you need to obtain the private key somehow. Yet you are only given the public key. Hint: How can you find the private key given the public key?
Apr
2
comment Security strength of RSA in relation with the modulus size
@mikemaccana: Indeed it does! Otherwise it would not be there. :) However, we're not sure of the value of $o(1)$ for values of $n$ that we care about. The complexity of the GNFS is heuristic. I recommend looking at this question and its answers/comments for some more discussion.
Apr
2
comment Security strength of RSA in relation with the modulus size
@mikemaccana: The $o(1)$ is little-o notation. As $n \to \infty$, the value $o(1)$ tends toward 0.
Mar
29
comment Can machine learning analyze random number generator?
It is not known to be impossible to formally prove that a CSPRNG is indistinguishable from random. We merely don't know how to prove it one way or another. If one way functions exist, we do have probably secure PRGs.
Mar
12
comment When is a cipher considered broken?
I disagree that "compromised" is a good word for that scenario, because "compromised" and "broken" are really very similar concepts. I would argue that unsafe is a much better word for "broken in a practical sense". Indeed, your very answer itself explains "compromised" as "no longer considered safe to use".
Jan
20
comment How much (home PC) CPU time is required to generate a prime number of a given size?
@K.G.: Ah, well, I did not intend for this post to really contain a serious prime-finding algorithm; rather I wanted to demonstrate that asymptotically, the task is not difficult, and real world improvements (like your suggestion) make that analysis messier.