All Questions

0
votes
0answers
10 views

Is there a public-key system that can chain?

Does there exist any asymmetric cryptosystem that has the following properties: If I know somebody's public key PBK_1 and my own key pair (PVK_2,PBK_2), I can construct a new public key PBK_3 such ...
0
votes
1answer
16 views

Key exchange without an underlying semigroup

I am wondering whether there is a general reformulation of perfect forward secrecy for 2 party key exchange in 2 messages using semigroups. I am looking for references, which would discuss such ...
1
vote
0answers
23 views

Does such cryptographic protocol exists?

A, B and C put x€, y€ and z€ in a pot, respectively. Suppose that anyone can withdraw from the pot as long as they prove they have that right and that the x€ that B sent are addressed to me. Is there ...
1
vote
1answer
59 views

How long does it take to crack RSA 1024 with a PC?

Using an Intel Core i5 CPU, how long does it take to crack RSA using a key size of 1024 bit (generated using a secure key pair generation function)? Suppose for instance that we have thousands of ...
-1
votes
0answers
9 views

BIP39 Path in ledger nano s [migrated]

On ledger nano S, you are given a BIP39 24 word mnemonic. What is the path to the address used? Is it m/44'/144'/0'/0/0 ? Say for example I use the address generated by the ledger nano s to store ...
1
vote
0answers
17 views

How to calculate RSA group signatures

RSA group/ring signatures, how are they calculated?
1
vote
1answer
20 views

SHA1 padding on length extension attack

I was recently trying to replicate a length extension attack on SHA1. I implemented the registers state and also the new padding implementation (with the whole of the message that I want to extend). ...
1
vote
1answer
40 views

confusion about LUKS encryption

from Can I clone a LUKS container? You can, but it breaks security, because the cloned container has the same header and hence the same master key. You cannot change the master key on a LUKS ...
0
votes
0answers
11 views

Attack Scenario for mutual key authentication protocol based on a Symmetric key cryptography algorithm

Here, the R is a challenge and KAB is a key known only by Alice and Bob. The +1, in R+1 is a nonce. I need to find 2 attack scenarios on how the protocol can be broken. I have been able to find one, ...
1
vote
1answer
22 views

Choice between appending or prepending nonces to ciphertexts

I understand that when using CTR mode, it is usually secure to append or prepend the nonce to the resulting ciphertext, whether the nonce is before or after the ciphertext being unimportant. However, ...
1
vote
1answer
137 views

Cipher Block Chaining - How do you change the plaintext of all blocks?

I've just read about CBC encryption and decryption and was wondering how you can change every plaintext block? Let's say you have an initialization vector, 3 ciphertext blocks, know each block-cipher-...
-1
votes
0answers
51 views

What is the difference between a prime field $F_p$ and binary field $F_{2^m}$ in the elliptic curves?

I am using elliptic curves to encrypt a VOIP application, but I can not understand the difference between using an algorithm based on a binary field or a primary field. I would like for someone to ...
0
votes
1answer
28 views

Where does the certification come from

In the book : applied Cryptography 2nd(Bruce Schneier), chapter 2 I don't understand step(5), the 'certification' didn't mention in previous steps. does it mean 'a statement that he has received this ...
2
votes
0answers
45 views

Usage of the nth-root function in cryptography

Having offered a fast integer nth-root algorithm to a bigint library that is also used for cryptography I was asked if it does its work in constant time, so I took a look at the literature to see how ...
8
votes
0answers
89 views

Is this paper's technique for factoring RSA 2048 with noisy qubits realistic?

A paper titled How to factor 2048 bit RSA integers in 8 hours using 20 million noisy qubits has just come out which proposes a technique to factor RSA keys with moduli up to 2048 bits with a design ...
0
votes
0answers
7 views

What state does a qbit look like before it collapses [migrated]

Which is the correct depiction of a qbit state showing the possibilities before it collapses? Is it like: MODEL 1: 1000 0100 0010 0001 MODEL 2: 1000 0100 0010 0001 0111 1011 1101 1110 MODEL 3: ...
-5
votes
0answers
29 views

design a secret sharing scheme [on hold]

Suppose you are an army cryptographer. In the army there are one General and five Lieutenant Generals. Your mission is to design a secret sharing scheme allowing one General and one Lieutenant General ...
1
vote
0answers
25 views

IETF Recommendations for preparation for PQC- clarify in what way they are referring to bits [on hold]

In the IETF mtg in 2017, in the recommended actions, are they saying leave enough flexibility in terms of bit usage for key sizes to throw in/switch out anything NIST picks out, or sufficient key ...
0
votes
0answers
38 views

Root Certificate Authority of National Identity Cards [on hold]

We're collecting a list of all the Root Certificate Authorities of National Identity Cards but due to language issues and the relative obscurity of the government pages on which they are listed, we're ...
1
vote
1answer
66 views

Do Weil, Tate, and Ate pairings exist on all elliptic curves?

I don't know much about the math behind elliptic curves. Do Weil, Tate and Ate pairings exist on all elliptic curves? If the answer is negative, then what pairings do MNT, BN and SS curves have? ...
2
votes
1answer
41 views

What does the number 256 in pairing curve BN256 indicate?

There are many pairing based elliptic curves like MNT curves, BN curves, SS curves etc., When we say BN256 curve, what does the number 256 indicate? Is it some group order or number of bits required ...
1
vote
1answer
53 views

Is there a concept of embedding degree for non-pairing based elliptic curves?

From this post, I learned the concept of embedding degree. Intuitively, if embedding degree of an elliptic curve $E(F_p)$ is $k$, it means there is a way to transform points in $E(F_p)$ to $F_{p^k}$. ...
0
votes
0answers
13 views

How would I get the issuer's public key from two RSA-signed certificates? [migrated]

I'm trying to get the issuer's public key from two SSL client certificates signed with a 2048-bit RSA key, SHA-256 hashing and PKCS#1 padding, as I only know the issuer's DN and I wish to verify all ...
0
votes
1answer
42 views

Signal Protocol Header key encryption initialization vector

In Signal Protocol when you use a Double Ratchet you have 2 options: Normal encryption = header + ciphertext Encrypted header encryption = ...
0
votes
0answers
10 views

Using Chameleon-HF-enabled security in practice

If one were to implement a digital signature scheme that is only EUF-CMA-secure when using Chameleon Hash Functions, would one actually use a Chameleon Hash Function or a standard cryptographic hash ...
1
vote
0answers
37 views

Construction PRF from PRG

As discussed here, a classic and secure construction of PRF from PRG is: $F_k(x_1x_2\cdots x_n) = G_{x_n}(\cdots(G_{x_2}(G_{x_1}(k)))\cdots)$ where $G$ is a secure pseudorandom generator. I was ...
1
vote
2answers
57 views

How to actually compute the statistical distance?

I have an algorithm for discrete sampling that I've defined. This is to say that $A$, upon input some pdf $p(x)$, outputs samples from the pdf $p(x)$. There are some nuances (you have to make the ...
2
votes
3answers
47 views

“Work factor” and “iteration count” nomenclature in adaptive functions

In adaptive functions like PBKDF2 / bcrypt I often read people refer to "iteration count" and others refer to "work factor", and they seem to be used interchangeably (even though they're not - the ...
1
vote
0answers
59 views

Is NIST testing all the round 2 submissions to quantum-resistant crypto?

Is NIST confirming the self-published quantum-resistant crypto round 2 data and do they make that available to the public when they do?
1
vote
0answers
50 views

RSA How to find the exponent ($e$) of the Public key with the values $p$ $q$ and an example are given

I'm wondering if it's possible to find the public exponent ($e$) with an example and the (rather small) values of $p$ and $q$ given. Currently the only option I found is bruteforcing this value, but ...
1
vote
0answers
27 views

Given a ciphertext $c$ and a public string, how do we check whether $c$ encrypts something that is roughly equal to the string without decryption?

Let $𝑓$ be an encryption function, then we have $c = f(m)$ for some bit string $𝑚$. Here, we also have pattern matching function $𝑔(𝑚,𝑚′)$ which returns true whether $𝑚$ matches roughly with $𝑚′...
0
votes
0answers
34 views

how to conver a raw public key to DER or PEM? [on hold]

Looking for a way to convert a raw key to DER or PEM format. below is the ECDSA(p256) public key which needs to be converted to PEM format or dER. ...
3
votes
0answers
37 views

Homomorphic encryption and zero-knowledge proof in one cryptosystem?

Does a cryptosystem exist that simultaneously has the properties of homomorphic encryption and zero-knowledge proof?
0
votes
1answer
61 views
1
vote
1answer
37 views

Signing a message using SPHINCS Hash-based Signature scheme

I have questions on “SPHINCS: practical stateless has-based signature” by Bernstein et al. And I really hope that someone can help me with it. To help me understand it, I read the https://...
0
votes
1answer
52 views

RSA and possible range of $\phi(n)$

If $n = p_1 p_2$ for primes $p_1 \ne p_2$, $\phi(n)$ is $\phi(p_1)\cdot\phi(p_2)$. Does that mean that the possible range of $\phi(n)$ is somewhat narrow, that $(p_1-1) \cdot (p_2-1)$ (that is, $\phi(...
-4
votes
0answers
29 views

Binary Cryptography Problem [on hold]

i have some problem about a binary crypthography. i have the code and the solution but i can't found the key to understand the meaning. our value is ...
0
votes
0answers
14 views

Is it possible to verify the requesting user for a REST transaction secured by JWT at a later date? [migrated]

I have a React (Javascript) single-page application that authenticates users via username/password/MFA to Keycloak, receives a signed JWT upon successful authentication, and then uses that JWT to call ...
1
vote
2answers
108 views

Does lagrange interpolation work with points in an elliptic curve?

Defining the lagrange interpolation for $x=0$ as $\mathcal{L} = \sum_{i=1}^{t+1} y_{i} \cdot l_{i}$ with $l_{i}$ as the lagrange basis polynomials. Does this hold if we apply the elliptic curve ...
1
vote
2answers
45 views

EC Key Compression

Using the secp256k1 curve, will the below yield the same result? Generate private key -> compress private key -> generate public key Generate private key -> generate public key -> compress public key ...
0
votes
0answers
21 views

How to securely store encryption keys in android? [migrated]

I want to know how to securely store encryption key in Android(API Level < 23)? What is the best scenario to protect encryption and secrete keys?
-2
votes
0answers
65 views

How to encrypt data when send over https [on hold]

I know its not practical to encrypt data when you send over https for widespread consumer use. But if i had to, how would i do that?. One way is for the server and client to agree upon an additional ...
4
votes
1answer
51 views

What makes the quadratic residuosity problem hard?

The quadratic residuosity problem is the problem of determining whether, for given $r$, $m$, $\exists a.a^2\equiv r\mod m$. This problem's believed to be hard to solve in general (e.g. an efficient ...
4
votes
0answers
43 views

Why did Rabin use $x(x + b)$ instead of just $x^2$ in the original paper?

Encryption in the original Rabin scheme took a message $x$ and computed $x(x + b) \bmod n$, where $0 \le b \lt n$ and $n$ is the product of two secret primes $p$ and $q$. The private key is defined as ...
0
votes
1answer
60 views

Is this man in middle atack possible in quantum cryptography? [duplicate]

Lets consider there is channel between Alice and Bob, sequered with quantum cryptography. To put it simple, Alice is left, Bob is right and the quantum states are 'up' ~ U and 'down' ~ D. Alice ...
1
vote
2answers
34 views

DES parity bits

The key is nominally stored or transmitted as 8 bytes, each with odd parity. According to ANSI X3.92-1981 (Now, known as ANSI INCITS 92-1981), section 3.5: One bit in each 8-bit byte of ...
1
vote
2answers
110 views

Can Reed Solomon parity blocks be used as an all-or-nothing transform?

Consider the following scheme: Perform an (N,N) Reed-Solomon encoding (i.e. N data blocks, N parity blocks) Drop the N data blocks and keep only the N parity blocks. Are these N parity blocks an all-...
1
vote
1answer
26 views

how do we calculate set intersection using homomorphic encryption?

I am new to this field. I want to learn how homomorphic encryption can be used for PSI. I am aware of other SMC protocols but I never understood how to use schemes like Paillier for PSI calculation. ...
0
votes
1answer
18 views

Group Encryption or Multi-Party Encryption

I came accross a privacy and cofidentiality problem in medical field where patients medical record is available to certain doctors in full, but researchers/pharmacutical companies can only view the ...
2
votes
1answer
27 views

LoRaWAN 1.0.2 Session Key Security

I am reading about LoRaWAN 1.0.2 specification. For the confidentiality and integrity of the comunication the protocol generate two session keys, the NwkSKey and the AppSKey (part 6.2.5 of the ...

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