Cryptography Stack Exchange Community Digest

Top new questions this week:

Minimal Assumptions in Cryptography

When do we call an assumption to be minimal assumption? What's the difference if we say just using assumption X the protocol Y is constructed instead of using minimal assumption X the protocol Y is ...

hardness-assumptions oblivious-transfer  
user avatar asked by Crypto_researcher Score of 4
user avatar answered by Mikero Score of 6

How to make a function which produces a hash of variable length?

I have been learning about OTP lately and I wondered, if I was to use it for encryption of a file (like a photo or even a video), I would need really looong key. Example program is simple: input is ...

hash one-time-pad sha-512  
user avatar asked by aturt13 Score of 2
user avatar answered by fgrieu Score of 3

Question about P and NP problem

There is a definition for NP shown below. Could anyone please explain why "By restricting the definition of NP to witness strings of length zero, we capture the same problems as those in P."?...

complexity snarks  
user avatar asked by fa william Score of 2
user avatar answered by Mahesh S R Score of 1

Why is the ciphertext output 32 bytes long when i encrypt a 16 bytes long plaintext by using AES-128-CBC

I am studying AES algorithm, as far as I know, encrypting a 16 bytes plaintext will result in a 16 bytes ciphertext. But I got a different result when trying to encrypt a 16 bytes plaintext using AES-...

encryption aes cbc padding  
user avatar asked by user25513320 Score of 2
user avatar answered by kelalaka Score of 4

Efficient NOT in set proof?

I am looking for a solution for a very specific problem, I have one, but I am not statisfied with it and it feels there must be a much more efficient way to do this. I have a hashed value of 256 bits. ...

zero-knowledge-proofs cryptocurrency commitments  
user avatar asked by ovanwijk Score of 1

Question of section 1.3 Intuition for Aborting in "Fiat-Shamir With Aborts: Applications to Lattice and Factoring-Based Signatures"

When I'm reading this paper "Fiat-Shamir With Aborts: Applications to Lattice and Factoring-Based Signatures" by Lyubashevsky. I have trouble understanding section 1.3 Intuition for Aborting....

public-key signature lattice-crypto fiat-shamir  
user avatar asked by Solaris Score of 1
user avatar answered by DannyNiu Score of 0

What is the XOR count of AES MixColumn matrix?

I am a beginner and I am learning about XOR counts, (Link to background: The 4 by 4 matrix used in the MixColumn operation in AES is [2,3,1,1],[1,2,3,1],[1,1,2,3],[3,1,1,2]. I ...

aes xor cryptographic-hardware  
user avatar asked by Kurious Koder Score of 1
user avatar answered by DannyNiu Score of 0

Greatest hits from previous weeks:

SHA-512 faster than SHA-256?

I'm getting this strange result that SHA-512 is around 50% faster than SHA-256. I'm using .net's SHA512Managed and SHA256Managed ...

hash sha-256 sha-512  
user avatar asked by ispiro Score of 75
user avatar answered by Stephen Touset Score of 76

Signatures: RSA compared to ECDSA

I'm signing very small messages using RSA, and the signature and public key are added to every message, which requires a lot of space compared to the actual content. I'm considering switching to ...

rsa signature authentication dsa  
user avatar asked by Maestro Score of 53
user avatar answered by poncho Score of 49

Should we sign-then-encrypt, or encrypt-then-sign?

Frequently, we want to send messages that are (a) encrypted, so passive attackers can't discover the plaintext of the message, and (b) signed with a private-key digital signature, so active attackers ...

encryption public-key signature protocol-design hash-signature  
user avatar asked by David Cary Score of 152
user avatar answered by D.W. Score of 116

What is the difference between MAC and HMAC?

In reference to this question, what are the "stronger security properties" that HMAC provides over MAC. I got that MAC requires an IV whereas HMAC doesn't. I also understood that MAC may reveal ...

mac hmac  
user avatar asked by TheRookierLearner Score of 58
user avatar answered by Seth Score of 86

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  
user avatar asked by Mike Ounsworth Score of 49
user avatar answered by mikeazo Score of 34

What is the length field in SHA-512 padding?

If I am using SHA-512 on a message and need to determine the padding field and length field, how do I determine the length field? I think I understand the padding, but not the length field. For ...

padding sha-2 sha-512  
user avatar asked by Jesse Score of 5
user avatar answered by Nova Score of 1

Why is writing your own encryption discouraged?

Say I want to write an encryption algorithm to communicate between me and my friend for this private use. How is that bad? E.g. I can take the word Hello and ...

user avatar asked by Pierte Score of 163
user avatar answered by Stephen Touset Score of 228

Can you answer these questions?

In Kerberos, is the "Authentication Server" the only "Trusted Third Party"? Or is "Ticket Granting Server" also a "Trusted Third Party"?

I know that AS (Authentication Server) is a TTP (Trusted Third Party) because it generates keys for two entities (for the client and the TGS). But what about TGS (Ticket Granting Server)? It also ...

keys symmetric protocol-design key-exchange kerberos  
user avatar asked by allexj Score of 1

How to choose the distribution of error and secret vectors in LWE-based KEMs

The general construction of a LWE-based PKE looks like the following: KeyGen : Secret vector, sk :$ s \leftarrow \chi_s^m$ Public Key, pk: ($A \leftarrow \mathbb{Z}_q^{m \times m}, t = As + e)$ where $...

post-quantum-cryptography lattice-crypto lwe kyber kem  
user avatar asked by VIKAS SRIVASTAVA Score of 1

is there any Openssl 3.x API for enabling and disabling FIPS mode?

i'm checking to see if there is any API or mechanism to enable or disable the FIPS Mode during the run time. Currently the only way to change the FIPS mode is to enable the algorithm_sect (...

openssl fips-140 fips programming-interface  
user avatar asked by Zoeb Vora Score of 1
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