Questions tagged [entropy]

Entropy is a measure of how predictable the outcome of a random process is, or how much uncertainty one has about an unknown quantity in one's state of knowledge, defined in terms of the probability distribution on possible outcomes or quantities.

Filter by
Sorted by
Tagged with
1
vote
1answer
28 views

Randomness extraction on correlated data in TRNG

True random number generator (TRNG) designs I read about mostly consist of two digital stages: Low-frequency sampling (of a physical noise source) Randomness extractor The noise signal is sampled at ...
2
votes
1answer
189 views

Randomness extraction from a Santha-Vazirani (semi-random) source

In a quest to better understand randomness extractors (in the context of TRNG post-processing), I read some papers about the von Neumann Extractor and Santha-Vazirani (SV-) sources. The von Neumann ...
0
votes
0answers
53 views

Correlations in ring oscillator PUFs

A bunch of silicon Physical Unclonable Functions (PUFs) designs rely on variations of the propagation delay (due to process variation) of signals in different path. In many cases, a challenge selects ...
3
votes
1answer
150 views

Use of scrambler LFSR for randomness extraction of semi-random source

I am using a linear feedback shift register (LFSR) in a scrambler configuration as a randomness extractor for a weakly random source. This source is semi-random (aka. Santha-Vazirani source): the bits ...
0
votes
1answer
65 views

Why Entropy is low for Python Fernet Encryption

I am using Fernet encryption from python cryptography.fernet and generated the key as below ...
4
votes
3answers
215 views

How to compute the dataset size required by dieharder tests?

I am trying to use the dieharder random number test suite. However, this suite requires massive amount of data (this paper claims 228GB for no rewinding for every test) for most of the tests. I'd like ...
0
votes
2answers
112 views

Does watching Youtube generate entrophy

Does watching videos (either online videos such as off youtube or saved locally) generate enough (if any) entropy to create secure encryption keys? I understand that some activities such as memory ...
2
votes
1answer
55 views

Does applying a “PushEntropy”-function increase security of a private key?

I was just reviewing the source-code of the NBitcoin-package. As far as i can see when you create a new bitcoin-keypair Key privateKey = new Key(); (without passing ...
1
vote
0answers
56 views

How efficiently can an attacker forge parts of a fingerprint?

If two devices do not trust each other yet, you can't simply send the correct fingerprint across: you have to manually verify it. I am looking into the security of comparing only random parts of a ...
1
vote
0answers
37 views

Exercise applying Leftover hash Lemma

Say that X is a (k; n)-source if $X\in\{0,1\}^2$, and the min-entropy of X is at least k. Answer the following questions: (i) Suppose that $l=128$; what is the minimal amount of min-entropy needed in ...
2
votes
1answer
117 views

How to ensure that a cryptographic implementation is reasonably sound/robust?

I know from the bottom of my heart how bad the idea of custom-crypto is. I absolutely concur with the recommendation that it should only be done by professionals who specialize in implementing crypto ...
1
vote
1answer
122 views

Low Encrypted Entropy on PDF File

Thank you for the answers, I have edited my questions. It is a known fact that encrypting the files increases the file entropy. You can see the average entropy values of encrypted and non-encrypted ...
1
vote
1answer
278 views

Should I calculate SHA-256 hash of a raw bytes of a token or it's hex encoding?

I have a system where I should generate a secret token for a user. The presence of a token is sufficient to grant access to some user-related data. I am generating a 4096 bit token from a ...
3
votes
3answers
150 views

Measuring entropy of a uniform distribution source

What is entropy? I do not understand it at all. One article states: When there is an equal chance for all items to appear, we have a uniform distribution. In uniform distribution the entropy is high....
0
votes
0answers
43 views

Quantum key distribution using BB84 protocol

Quantum key distribution using BB84 protocol. The Secure key rate $R$, is given by $$ \quad R=1 - 2h(e_b) \tag{1}\label{q1}$$ where $e_b$ is the quantum bit error rate (QBER), $h(x)$ is the Shannon ...
1
vote
0answers
99 views

In my opinion a lot of encryption paper have small contribution in terms of security improvements [closed]

I used to saw a lot of encryption papers that have small significance in security improvements especially in terms of entropy, histogram and coefficient correlation especially in image encryption. Why ...
1
vote
0answers
33 views

How is it possible to prove that Shanon entropy does not change applying any bijective function to X? [duplicate]

I was wondering how is it possible to mathematically prove that Shannon entropy does not change when applying any bijective function to X? For instance H(X) = H(f(X)) assuming that f is invertible and ...
0
votes
1answer
98 views

How to prove that permutation and substitution ciphers satisfy H(X) = H(Y) in Shanon Entropy?

I was not able to mathematically prove that all permutation and substitution ciphers satisfy H(X)=H(Y) if we say that Y is the set of ciphertexts while X is the corresponding set of plaintexts in ...
1
vote
2answers
345 views

Recovery Passphrase Collission for BIP-39 and BIP-44

Referring to the standards of [BIP-39] and [BIP-44]: a 'master password' consisting of 12 words uniformly selected from a 2048-word dictionary corresponds to 128 bits of entropy, that is then used as ...
0
votes
1answer
90 views

Shannon information entropy value of 64 bit data?

So basically i have a set of float data, its value ranges from -1.3117 to 1.7956 and then i convert this data into 64 bit binary value(assuming it is originally 64 bit double float). After that, i ...
0
votes
1answer
81 views

What Permutation Entropy really is?

I was wondering about what is permutation entropy(PE). Then, I came to know this paper which describes PE. Now, let's assume that we have a pseudorandom permutation that is generated using an entropy ...
0
votes
0answers
76 views

How does the entropy of $r$ influence the security of the one-time pad $F_k(r) \oplus m$?

In an one-time pad scheme, $s \oplus m$ is uniformly random for any $m \in \{ 0,1 \}^\ell$ if $s$ is uniform in $\{ 0,1 \}^\ell$. By the security of PRF, it seems to be secure to replace the truly ...
2
votes
1answer
107 views

How to verify the claim of entropy available made by Linux 4.5?

The Linux kernel has an entropy source and it estimates its amount of bits in the device /proc/sys/kernel/random/entropy_avail. How can I verify that this number ...
3
votes
2answers
275 views

Formula for bits of entropy per bit, when combining bits with XOR

Assume that bits $A$ and $B$ each have .5 bits of entropy per bit. The two-bit result of the concatenation $A‖B$ has 1 bit of entropy total, and it retains the entropy density of .5 bits of entropy ...
2
votes
3answers
168 views

Where can I find a sample of data with a known entropy to see how well NIST SP 800-90B does on it?

I'd like a sample of true random data from a source that has a known entropy. It's not easy to even produce true random data in sufficient quantity --- much less know the entropy of the source. For ...
2
votes
1answer
142 views

Why does it make sense to use min-entropy for measuring cryptographic random data?

Comments on Cryptographic Entropy Measurement seems to challenge the heart of NIST SP 800-90B, which proposes min-entropy as a conservative measure of entropy produced by hardware source. [The idea ...
1
vote
2answers
80 views

What adequate tools are available for estimating entropy?

This question seems to touch on the apparent fact that NIST SP 800-90B is not suitable for estimating entropy produced by sources that are not uniform, despite being IID or non-IID. It also seems ...
2
votes
2answers
108 views

Can I measure entropy through compression only?

Say I have a file containing words from the English language. Not meaningful text, just a repetition of a few words. The original size is 1559454 bytes and it is compressed by a certain program to ...
5
votes
2answers
316 views

What's wrong with NIST SP 800-90B?

NIST SP 800-90B offers various tests for estimating entropy. They also offer an implementation of these tests. With their program called ea_iid, estimating ...
0
votes
1answer
119 views

Is this cumbersome strategy to produce a ridiculously strong password valid?

I'm writing something where somebody wants to have a ridiculously strong password for a file and yet be sure that he will always be able to reconstruct it. The way I have thought of this might be a ...
6
votes
4answers
1k views

Bits of entropy needed to choose a random element from a list?

Suppose I want to choose a random element from a list of size $2^n$, for any integer $n$. (Here, random is to mean an equal probability of selecting every item.) My intuition says I'd need $n$ bits of ...
2
votes
3answers
119 views

Is it absurd to estimate entropy from a sample?

To tell the exact entropy of a source, all I need to do is to use Shannon's formula $\sum -p(i) \lg p(i)$, where $i$ is the $i$-th element of the alphabet emitted by the source. Therefore, the only ...
4
votes
2answers
175 views

Are the GPS coordinates a good source of entropy?

Are the GPS coordinates (latitude and longitude) a good source of entropy? If yes, why? If no, why? The question would investigate on the fact if the GPS location data can be used as source of entropy ...
0
votes
2answers
125 views

How to calculate the entropy for a fixed length random passwords which has restrictions on the type of characters used

If we have a set amount of usable characters, but no other restrictions on the potential characters in a completely random fixed length password, we can easily calculate the entropy by doing: $\log_2(...
1
vote
1answer
233 views

I do many searches but can't find any explanation about “AES analysis using entropy”

I found this scenario in CRYPTOOL2 templates but there is no explanation how entropy is used. There is just a short description "This template shows how to use a brute-force search to attack an ...
0
votes
1answer
103 views

Symmetric key validity hypothesis?

Can I use something like Shannon entropy to determine the suitability of a symmetric key? I found a symmetric key which wasn't generated using a CSPRNG and it had a very low Shannon entropy. I ran an ...
1
vote
1answer
858 views

Practical sources of entropy on an Android device?

What Android API's can be used a practical sources of entropy ? Given the requirement of sourcing entropy on the phone for purposes of seeding a PRNG, what are good options ? Edit: I have a hard ...
3
votes
1answer
108 views

Randomness extractors from Bourgain’s breakthrough- applications?

Some exciting progress to pure mathematics is due to Bourgain Springer - Multilinear Exponential Sums in Prime Fields Under Optimal Entropy Condition on the Sources with applications to randomness ...
3
votes
2answers
249 views

How much entropy do I need to add to passwords if they are NOT used in conjunction with logins

I'm building a system to authenticate users to a website via a single use login token. This token can either be included in links OR typed in directly by the user as a code. Because of that second ...
2
votes
3answers
180 views

How to derive a passphrase from a hash?

I'd like to generate a passphrase derived from a hash fingerprint. The passphrase consists of short and human-pronounceable words from a phonetically-distinct wordlist. The derivation is a one-way ...
1
vote
2answers
127 views

Entropy test vs frequency analysis

I'm currently doing the cryptopals challenges and for it's first set of problems it tells you to use frequency analysis of occurring letters to determine the likelihood of a key guess being correct ...
18
votes
2answers
4k views

A website that identifies an RNG from its output

This happened during a discussion of RNG entropy, and the difficulty of verifying the level of entropy in a long sequence of bits (e.g. a private key.) A colleague of mine told me about a website ...
6
votes
2answers
848 views

How to analyze the off-by-one error's impact on the entropy of the result?

I'm reading Jean-Philippe Aumasson's book Serious Cryptography to learn more about cryptography. On page 37, the author gives an example of Cryptocat's off-by-one error in its PRNG implementation in ...
1
vote
2answers
160 views

Iterative hashing increases number of security bits?

Whatsapp uses 5200 iterations of SHA-512 over user's public key and identity according to WhatsApp Security Whitepaper. I wonder why? According to: Why iterate 5200 times when computing Safety ...
1
vote
0answers
81 views

libgcrypt and rdrand usage

For some reasons, I was looking into libgcrypt source code and found this. If I understand this correctly, while asking to use /dev/random for some bytes, it actually checks first if rdrand is ...
1
vote
2answers
146 views

Losing entropy after re-hashing a hash

Suppose you have a string AAA that was hashed with SHA1 to produce 606ec6e9bd8a8ff2ad14e5fade3f264471e82251. If I rehash ...
8
votes
4answers
10k views

How hard is it to guess a 8 digit PIN?

Say that there are different live situations where you have to select own PIN numbers. Can someone say if it is possible to guess a 8 digit pin within 3 tries, given any methods or resources? Is ...
1
vote
0answers
152 views

What is the formula to calculate password entropy? [closed]

I saw in another thread: Is using 7-8 random words from all words of a language as password a good idea? These calculations: If we assume that English has 171,476 words. Then with 8 words the ...
1
vote
1answer
29 views

Does concatinating mutliple digests of hashes from CSRN result in a CSRN?

Kind of a noob question. Suppose; We generate 1,000 cryptographic-ally secure random numbers & store each of them in an array1. For each number in this array1, we take the hash sha256(CSRN) then ...
0
votes
0answers
160 views

Computing guessing entropy (average rank of the correct key) in attack using deep learning

I am looking for help with some issues that I have about the guessing entropy (GE) in side-channel attacks context. I have read some papers where GE is used as a metric to measure the attack's ...

1
2 3 4 5
7