Cryptography Stack Exchange Community Digest

Top new questions this week:

What were Alan Turing and their team searching before doing KPA in the movie "The imitation game"?

I just watched the movie "The imitation game" (2014) which is based on Alan Turing's biography. At some point in the movie the machine built by Turing wasn't fast enough to decrypt the ...

known-plaintext-attack history enigma  
asked by melfnt 4 votes
answered by Daniel S 5 votes

How to securely derive a key from a list of sorted random bytes?

Is it possible to derive a secure cryptographic key from an array of sorted bytes, assuming the bytes themselves were generated in a secure manner (say, from quantum phenomenon)? What would be the ...

asked by Jakub 4 votes
answered by Daniel S 4 votes

What's the main difference between the Schnorr identification scheme and its Smart-Card implementation?

This question arises because I couldn't find any official paper for the Schnorr identification scheme, but only for the Smart-Card implementation of it. Also, it seems that everyone, when talking ...

zero-knowledge-proofs discrete-logarithm schnorr-identification  
asked by Andrea Farneti 4 votes
answered by fgrieu 6 votes

Is KMAC just SHA-3-256(KEY || message)

According to keccak strengths you have: Unlike SHA-1 and SHA-2, Keccak does not have the length-extension weakness, hence does not need the HMAC nested construction. Instead, MAC computation can be ...

hash mac sha-3 keccak kmac  
asked by Finlay Weber 4 votes
answered by kelalaka 5 votes

BGW multiplication by Gennaro et al.: Why does H(x) have exactly degree t and why is $2t + 1 \le n$ necessary?

With this question I am referring to the BGW multiplication by Gennaro et al (PDF here). The multiplication is described on the 4th page. (Another source for me was "A pragmatic Introduction to ...

secret-sharing multiparty-computation threshold-cryptography  
asked by ht332932 3 votes
answered by Daniel S 0 votes

Difference between Non-uniformly random and Uniformly random

I am reading up on Key Deriving Functions (KDF) and in a section of the Real-World Cryptographic book by David Wong, a comparison is being made with Pseudorandom number generator (PRNG). And one of ...

random-number-generator key-derivation randomness entropy  
asked by dade 3 votes
answered by fgrieu 5 votes

How to decide if a point on a elliptic curve belongs to a group generated by a generator g?

In the elliptic curve encryption scheme, there is a cyclic group generated by a base point $G$ on the elliptic curve. Given a random point on the elliptic curve, is there a way to decide if the random ...

public-key elliptic-curves group-theory  
asked by mactep Cheng 2 votes
answered by kelalaka 4 votes

Greatest hits from previous weeks:

What are the differences between .pem, .csr, .key, .crt and other such file extensions?

I'm new to SSL / TLS, and I want to work with the OpenSSL toolkit. What do .pem and .csr stand for? I do know that ...

tls openssl terminology file-format  
asked by Richard R. Matthews 114 votes
answered by Maarten Bodewes 166 votes

Differences between the terms "pre-master secret", "master secret", "private key", and "shared secret"?

Both crypto.SE and security.SE have excellent Q&As about how TLS generates session keys (I have linked some at the bottom). In reading these threads I'm having troubles with terminology since the ...

keys tls key-exchange terminology  
asked by Mike Ounsworth 44 votes
answered by mikeazo 32 votes

What's the fundamental difference between Diffie-Hellman and RSA?

What is the difference in the purpose of DH and RSA? Aren't they both public-key encryption?

encryption public-key rsa diffie-hellman  
asked by user541686 38 votes
answered by user541686 34 votes

Who verifies the trust of certificate authorities?

Background I am a novice in the field of cryptography and cyber-security, and while studying asymmetric-key encryption, I learned about the potential of a man-in-the-middle attack. To mitigate this ...

public-key certificates  
asked by AlanSTACK 76 votes
answered by JimmyJames 48 votes

What is a cryptographic "salt"?

I'm a beginner to cryptography and looking to understand in very simple terms what a cryptographic "salt" is, when I might need to use it, and why I should or should not use it. Can I get a ...

encryption hash passwords salt password-based-encryption  
asked by Bhavik Ambani 128 votes
answered by MartinSuecia 186 votes

What is U2FsdGVkX1?

Using CryptoJS 3.1 I noticed that using 3Des, the encrypted message always start with U2FsdGVkX1 Why is the first part of the encryption always the same? What information does this hold and how ...

encryption implementation 3des  
asked by Thomas 11 votes
answered by woliveirajr 12 votes

Simply put, what does “perfect secrecy” mean?

I would like to ask for a clear (but maybe not so deep) explanation of what the term "perfect secrecy" means. As far as I have researched and understood, it has to do with probabilities of assuming ...

one-time-pad terminology security-definition  
asked by Emyr 33 votes
answered by Cryptographeur 21 votes

Can you answer these questions?

Need help to understand RSA common modulus attack to get private key

I'm learning about common modulus attack and learned that public modulus attacks can find out the private key. Assume there are 2 users with public and private keys $(e_1, d_1)$ and $(e_2, d_2)$. ...

asked by domiee13 1 vote
answered by fgrieu 0 votes

Exact security requirements for extendable output functions (XOF)?

In the FIPS202 document "SHA-3 Standard: Permutation-Based Hash and Extendable-Output Functions" an extendable-output functions is defined as: An extendable-output function (XOF) is a ...

security-definition sha-3 xof  
asked by cryptobeginner 1 vote

Difference between an authentication scheme and a identification scheme in ZK proofs?

EDIT: I want to specify what I know about schemes security: Authentication schemes: P can prove V he is P, and nobody else can prove V that they are P. Identification schemes: P can prove V he is P, ...

zero-knowledge-proofs security-definition  
asked by Andrea Farneti 2 votes
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