# 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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### Does hashing a secret/seed make it effectively 2X less secure?

In many cryptocurrency projects I noticed that 32-byte seeds/secrets are hashed to arrive at new 32-byte keys. The reason why is because you can then, with the addition to an index, use the same seed ...
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### Password entropy requirements for online dictionary attacks on OPAQUE?

My understanding is that for PAKE protocols such as OPAQUE (https://eprint.iacr.org/2018/163.pdf), the the adversary has no choice but to just do online attacks on the password. If this is true, I ...
1 vote
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### How to calculate entropy of a specific cryptosystem?

I want to calculate the entropy of a specific cryptosystem such as the Caesar cipher or Vernam cryptosystem etc but I don't quite understand how to do so. Any help?
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### What are the key difference between Shannon entropy and Guessing Entropy?

Any body can explain, what are the key differences between Shannon entropy and Guessing Entropy? In some research I got entropy uses binary search or balanced Huffman tree. Guesswork uses linear and ...
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### Is the Secret sharing scheme thresholds of variable of interest shared related with the entropy of the variable?

Is the $t$ out of $n$, namely $(t,n)$, threshold in the secret sharing scheme related to the entropy of the random variable that is shared according to the scheme? What changes in the secret sharing ...
1 vote
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### Why Entropy to be defined as Joint Probability Distribution Sum?

From Stinson's book, during the demonstration of the following Theorem which says: $H(X,Y) \leq H(X) + H(Y)$, with equality if and only if $X$ and $Y$ are independent random variables. The author ...
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### How can a generate a key with defined key size with a hash function with its security/internal state shorter than the key?

Let's suppose I took a high resolution photo full of entropy and I want to convert in a key with 2048-bits of security. Practically all the known hash algorithms have maximum 512-bits of security. Is ...
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