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Is using a cofactor to find a base point only for performance reasons?

For elliptic curve cryptography, the procedure to find a base point that generates a subgroup with order $n$ is: Calculate the order $N$ of the elliptic curve (using schoof's) Choose $n$. $n$ must be ...
11 views

Can/Should you use a private key as source of randomness?

Assume we have a given private key and want to generate x random values. Would a scheme where we generate the random values using ...
18 views

What's the probability distribution of 3DES keys' key check values?

Do the key check values of two-key 3DES keys have a uniform distribution? If not I'm curious as to what the distribution is. I ask because I want to know how safe it is to use a key's KCV as an ...
20 views

How can we measure the security levels of post-quantum cryptographic algorithms? Is there a standard way of this measurement?

How do we measure the security levels of Post Quantum Cryptographic algorithms such as: NTRU Prime, Saber, Kyber,...that are submited to NIST PQC Standardization Process(Competition) in general? I ...
15 views

Clear Data Block Error

I am encrypting a 3DES key with RSA public key and when trying to decrypt it with RSA private key, it gets an error "Clear Data Block Error". What does it mean and how to resolve it? Data to ...
7 views

What is the difference between the Fully Homomorphic BFV and BGV schemes?

When I read about BFV or BGV, they all look similar: they use polynomials from $\mathbb{Z}[X]/X^n+1$ as secret keys/pubic keys, etc. What is the main difference?
8 views

Prover cost of QAP based zkSnark

In CGPR [https://link.springer.com/content/pdf/10.1007/978-3-642-38348-9_37.pdf] Section 3.5, it is mentioned that the cost of prover is $O(|C| \log(|C|))$, given the size of the circuit is $|C|$. It ...
40 views

How to find the 6 main properties of cryptographic hash functions when implementing a hash function?

According to this there are at least 6 "properties" all cryptographically secure hash functions strive to attain: Deterministic: the same message always results in the same hash; Quick: it ...
461 views

Factoring 2048-bit integer with quantum computer?

In this paper, there is a statement in abstract as: "Our construction uses $3n + 0.002n log(n)$ logical qubits, $0.3n^3 + 0.0005n ^3log(n)$ Toffolis, and $500n^2 +n^2 log(n)$ measurement depth ...
6 views

zkSNARKS - unable to understand the usage of polynomial to verify some condition

From Vitalik Buterin's Blogpost - An approximate introduction to how zk-SNARKs are possible From the sub-topic "Comparing a polynomial to itself", I understood till here In other words, any ...
33 views

How does an attacker decrypt a hash function by looking for linearity?

Reading the selected answer to Designing a hash function from first principles rather than depending on heuristics is very insightful. The section on "nonlinearity" suggests that making ...
37 views

Is it possible to tell if a point on an elliptic curve is less than half of the curve's order? If I have a point $𝐴 = [a]𝐺$ on a curve with prime order q, is there an efficient way to know that $a &... 0answers 26 views Control the error bound when using HElib CKKS I'm using HElib CKKS to do experiments and wondering if it's possible to control the error bound in each basic operation such as multiplication, encoding, and rotation. I have this question is because ... 0answers 106 views Where did Whitfield Diffie say "If you can make random numbers, you can have a private conversation"? I've seen the following (alleged) quotation on this site and other places:- If you can make random numbers, you can have a private conversation. -Whitfield Diffie. Yet we (Google & me) can't ... 1answer 13 views single slot operations on SIMD fully homomorphic polynomial According to https://eprint.iacr.org/2011/133.pdf and many other papers, there's an isomorphsim between the space of polynomials and its coefficients. So, at least in the BFV scheme, we can do:$$p(x) ... 0answers 30 views Why can’t you reverse engineer a hash function? [duplicate] If you can hash a value one way, why can’t you reverse the hash, turning the hash into one of the many possible inputs, that still gives the same hash? 1answer 56 views Understanding the algebra behind GCM's security I would like to understand the algebra behind GCM's security. Before I ask my questions, let me state my understanding of the math behind GCM. If correct, my questions are at the end; if incorrect, ... 2answers 159 views What could a_0=s in Shamir's secret sharing scheme represent? What could$a_0=s$in Shamir's secret sharing scheme represent? As we already know in a$k$out of$n$secret sharing scheme, a secret is split in$n$parts however only$k=t$parts (of a polynomial ... 1answer 40 views How to guarantee that a ZKP was generated honestly? The following extracts were taken from the Zero-Knowledge Proof page on Wikipedia: In cryptography, a zero-knowledge proof or zero-knowledge protocol is a method by which one party (the prover) can ... 1answer 43 views DIY: password key derivation tool using PBKDF2 / HMAC First of all, I don't want to reinvent the wheel, just want to build my own car. Non-product environment; only for fun and entertainment. The goal is to use a single private (and never published) ... 0answers 18 views Track crypto wallets voting on certain platforms [closed] Is there a way to track if a specific wallet has submitted proposals and/or joined the voting on governance proposals such as snapshot, uniswap and similar governance proposal platforms? Is there an ... 1answer 41 views Can voters be authorities at the same time? There is an encryption scheme where the votes are encrypted with ElGamal and the decryption key is the secret that is shared among the authorities. After everybody voted they publish their part of the ... 0answers 20 views Game server shared key security We are creating a competitive online multiplayer game, clients connect to a central match maker server through HTTPS, after a match has been created a game server will be launched. The match maker ... 0answers 29 views What kind of transactions that are processed on the blockchain? [closed] I have been watching MIT lectures on blockchain taught by Gary Gensler. What I understand form his lectures is that a blockchain is a record of transactions that it is stored on each computer that is ... 1answer 57 views Public-Key Encryption with Privilege Access: is it possible? Let be Alice, Bob, and David three people. They all have public-key cryptographic system: private key and public key. Is there any way, in some known cryptographic system (RSA, Elliptic Curve, etc.), ... 1answer 40 views Davies-Meyer block cipher and IV I have three questions regarding Davies-Meyer construction : What is the name of the underlying block cipher? How is generated the first input hash value (IV) passed to the block cipher? What is ... 0answers 6 views How to export ed25519 public key from []*pkcs11.Attribute [migrated] I generated an ed25519 key pair with golang PKCS11 library branch v3 (it is connected to SoftHSM2): ... 1answer 41 views An equivalent definition for shamir secret sharing? Taking into account this paper I will write here a definition that the authors provide.$\textbf{Definition:}$(linear secret sharing scheme). A$(t,n)$secret sharing scheme is a linear secret ... 1answer 46 views Help me to solve 3 Pass DiffiHellman protocol I am trying to solve 3pass Diffihellman problem. However, I could not solve it. Is there any specific rule exist to select a1 and b1 or problem in the calculation. Please help me to solve this problem.... 1answer 36 views RC4: Known plaintext key, unknown key derivation I am working with an older piece of software that generates encrypted backups that I'd like to decrypt. I have a plaintext key, a few examples of encrypted data and I'm pretty sure the data is ASCII, ... 1answer 46 views Is this simple Proof of Work algorithm based on SHA256 susceptible to length extension attack? Each block's contents are hashed into 32 bytes using$\operatorname{SHA-256}$(call this string$a$). In order for the block to be accepted, there must be a 256bit nonce (call this string$b$) ... 0answers 44 views Decryption of an El Gamal re encryption mixnet I have interest in e-voting and am currently trying to understand El Gamal re-encryption mixnet. I understand how El Gamal encryption works and how mixnet works but what's not cristal clear for me is ... 1answer 63 views How many combinotaion of all$n$players are needed to reconstruct the secret in a$(k,n)$-treshold secret sharing scheme? In a$t+1$out of$n$secret sharing scheme where there is a network of$n$players, in order to reconstruct the secret$t+1<n$players are needed to share their parts$(x_i,f(x_i))$so as the ... 0answers 86 views SHA-256 Hash Crack Suppose, If a SHA-2 hash does get broken completely with hardly any power, where would it get reported and is there currently a bounty on it? 1answer 26 views Secret sharing questions I would like to make a few questions about Shamir's secret sharing scheme and. To begin with, I am starting with the next theorem that determines the intuition of the whole theorem.$\textbf{Theorem:}$... 1answer 37 views How to define a cryptosystem when the encryption-decyrption scheme is based on Shamir's secret sharing scheme? I would like to make a parallelism between Shamir's secret sharing scheme and how to define a cryptosystem where the encryption scheme is based on secret sharing. To begin with I do not know if there ... 0answers 30 views Public key stored in PKI [closed] In a public key infrastructure how does a User A communicate with the user B? How does user A send his public key to user B ? Where is a public key stored where do they retrieve it from? This question ... 1answer 22 views Could we use permutation polynomials for Shamir's secret sharing scheme? Could we use permutation polynomials for secret sharing scheme like Shamir's? The say that they induce a bijection over$\mathbb{Z}_p$what does this mean and how does it helps? 1answer 16 views What is the advantage of AES key warp as opposed to adding a random nonce? I'm interested in methods of wrapping an AES DEK (Data Encryption Key) using AES KEK (Key Encryption Key). Is there an advantage to using AES key wrap (rfc3394) as opposed to simply adding a random ... 0answers 25 views Privacy preserving functions vs secure multi-party computation As we all know, secure multi-party computation allows us to run a certain computation/function on private inputs contributed by different parties (that do not necessarily trust each other). The ... 0answers 31 views Is there a function-hiding functional encryption for quadratic polynomials? Recently, I have found research papers about the functional encryptions for inner products and quadratic polynomials. For inner products, there are a few papers which focus to construct efficient ... 1answer 39 views Is it possible that PracRand did not detect looping of the generator? I'm testing my own PRNG generator which should has period$2^{38}$bytes. So after exactly$2^{38}$bytes it should start repeat. But PractRand find no anomalies after$2^{39}$bytes. Could it be that ... 1answer 116 views Is the STARK Curve a SafeCurve? SafeCurves defines criterias for choosing safe curves in elliptic-curve cryptography. STARK Curve defines a Stark-friendly elliptic curve that can be used with ECDSA. I was wondering: Is the STARK ... 1answer 61 views Baby steps with example, looking for an "AES for Idiots" type of explanation Countless examples all over on implementation of AES. None of these actually make sense to someone with zero cryptographic or advanced mathematical experience. This => too abstract & technical..... 1answer 23 views Does CMS AuthEnvelopedData type provide message authentication? I was looking through the S/MIME Message specification (RFC 8551) to find out what security services it offers. Section 2.4.4 of this document describing AuthEnvelopedData content type (which uses the ... 0answers 15 views openssl can't find configuration file [closed] Trying to get self-signed root certificate: sudo openssl req -x509 -newkey rsa -out cacert.pem -outform PEM Looks like openssl can't find configuration file and ... 0answers 53 views how do you prove you are not a bot with a zero knowledge proof? I communicate with another person online, I know he is a person because sometimes he also writes real messages but at random timeframes whenever I send him a message he only responds with a dot maybe ... 0answers 23 views Centrality of Gaussian distribution for LWE error Consider the LWE problem. Let$A$be an$m \times n$matrix,$x$is an$n \times 1$vector,$u$is a$m \times 1$vector, and$e$is sampled from a Gaussian distribution. We are given either$Ax + e ~~...
I will try to define easily the cryptographic system of this paper. The author designs a communication game for $N$ players. The private information of every player is denoted as $t_i\in T_i$ and ...