# 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.

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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
55 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### AES256 key entropy requirements

Is this encryption method sensitive to weak keys? Is there any reference in the NIST on the AES key's entropy? (For example, must it have been generated from a TRNG?) Can I safely use the Microsoft ...
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### how to measure/calculate guessing entropy for side channel attacks

I was going through the paper (https://link.springer.com/chapter/10.1007/978-3-319-66787-4_3), and I came across where authors says that accuracy alone is not enough as an evaluation metric and ...
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### Can we estimate the amount of entropy required to generate an RSA key?

Of say 4096 bits as is a default GPG master key. I can manage the first one or so almost immediately on Ubuntu. It then runs out of entropy when generating several more RSA keys, and I'm forced ...