Usage of randomness (i.e. non-predictable data, usually in the form of bits or numbers) for cryptographic purposes.

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2answers
2k views

How does the rand() function in C work? [closed]

I want to know how rand() works (even when I don't provide any seed how it produces PRNs?) thanks!
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1answer
336 views

How to generate a random polynomial of degree $m$?

I am trying to do a homework in which implement a variation of this paper and I don't know how to generate a polynomial of degree $m-1$. This polynomial is used to generate the $y_0$ and $y_1$ values. ...
3
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1answer
243 views

Crypto puzzle as proof of randomness?

I need an untrusted client to generate a random public/private keypair (in particular, an Ed25519 keypair, which can be generated really fast), but I'm only allowed to see the public key. The ...
4
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1answer
241 views

Using chi square for distinguishing between compressed and random data

I am trying to find some measurement for identifying and distinguishing between compressed and random data. I tried this first by computing the entropy of such data, the entropy value is extremely ...
3
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4answers
601 views

Randomized algorithms and the one time pad

The way I understand it, an algorithm is said to be randomized if it uses randomness as part of its logic (quoting Wikipedia). Now, in the case of encryption algorithms, I assume this means that for ...
2
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1answer
787 views

How to test distribution of a hash function?

From what I've found, it is generally accepted a cryptographic hash function like SHA-2 has an evenly, randomly distributed output. Is there a way to test this without running through the entire ...
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1answer
242 views

data structure of random / compressed data

can anybody explain to me what data structure results after data is compressed? I just try to find out the difference between random data and compressed data, the entropy of both is very high while ...
3
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2answers
277 views

Is just a bit of random, “fully random”?

I understand that hashing a datetime is a pseudo-random number, and not good in a security context. But what about hashing a datetime plus a truly-random but constant string (just a string that an ...
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2answers
1k views

Are mouse movement coordinates useful as a seed for a RNG?

Is it good to use a mouse movement as a 64-bit random seed for a Pseudorandom Generator like AES in Counter Mode? Should I only need to get the X and Y coordinates of the mouse movement?
2
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1answer
286 views

Conforming Randomness To An Alphabet

Imagine that we're trying to create a function to generate a random string conforming to a user-supplied alphabet. That way, users can generate random strings with given characters. Something like: ...
0
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1answer
150 views

Combatting traffic shape analysis with spurious packets

I was reading a question about combatting traffic analysis, and a thought occured. If I send random junk messages periodically, would that defeat traffic analysis? The messages would contain some ...
2
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2answers
1k views

How to decrypt this RSA-like cipher

Suppose we have a RSA-type Modulus $n = pq$ with $p,q$ prime. We also pick a random public exponent $e$ with $\gcd(e,\varphi(n)) = 1$ and compute the private exponent $d$ with $de \equiv 1 ...
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2answers
424 views

How can encryption involve randomness?

If an encryption algorithm is meant to convert a string to another string which can then be decrypted back to the original, how could this process involve any randomness? Surely it has to be ...
7
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1answer
305 views

How to enhance randomness of AES?

I'm using PHP to encrypt a string and Java to decrypt it on a remote server. To perform the encryption, I'm using the strategy that can be found here. My problem is that the strings I encrypt are ...
3
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1answer
216 views

Is a subset of a random set still random?

Suppose you have an infinite list of random bytes, and you select the first N bytes that correspond to printable ASCII characters. Is this list of N bytes still as secure (e.g. for the purpose of a ...
12
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3answers
2k views

What is the use of REAL random number generators in cryptography?

I understand the use of pseudo-random number generators. I am not getting mixed up between these and "real" random number generators. However, I don't understand for what a real random number ...
5
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4answers
941 views

Stretching a random seed to maximize entropy

I'm using a random number generator that requires me to pass it a big (several kilobytes) pool of random data for initialization. I've gathered entropy from various system metrics (free memory, ...