Questions tagged [public-key]

An asymmetric cipher is an encryption scheme using a pair of keys, one to encrypt and a second to decrypt a message. This way the encrypting key need not be kept secret to ensure a private communication. Similarly in public key authentication, the verification key can be public and the signing key private.

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Proof that exchanged variable was not modified with MITM

If I understand correctly, the core of man in the middle attack is in being able to replace an exchanged variable (public key) with another. Hence to detect a MITM one needs to check if the exchanged ...
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How secure is it to use a 128-bit random seed to derive a 256-bit key for seeding key-pair generation?

We are developing an open-source peer-to-peer app, Mapeo, designed for users with low technical experience (and no email or phone) to collect data in offline environments. We are generating their ...
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Would being able of factoring integers efficiently have some consequences over Elliptic Curve Cryptography?

Let's assume you can factor integers in a very efficient manner. Would that endanger the security of e.g. elliptic curve cryptography, or is there no link between the two ? You can often read that ...
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Is qTesla Secure?

qTesla is a signature scheme and a submission to the NIST post-quantum standardization process, which made it to the second round. It is based on the hardness of RLWE. The NIST round 2 status report ...
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Does SHACAL-2 have collision resistance?

I am trying to find if a design of mine SHACALheader(payload) ⊕ header will have more collisions than if we just concatenate Hash(datagram) := H( H(header) || H(payload) ) ? I am fairly new to ...
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How to convert plaintext to element of cyclic group in Cramer-Shoup cryptosystem

I am trying to implement a cramer-shoup cryptosystem but I don't understand how to work with the plaintext I want to encrypt. From what I understand, the plaintext needs to be converted to an element ...
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ZKP: Prove that >18 while hiding age

I am relatively new to cryptography, but I've been programming for a while. Here's a story that sets well the problem I'm trying to solve: Alice has a digital passport that's signed with her ...
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Modes of operation for public key encryption [duplicate]

Why do we not define modes of operation for public-key encryption just like how they are defined for block ciphers?
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Is asymmetric decryption guessable?

I am not an amateur in cryptography so this might be a very basic question. I am interested to know if there exist ciphers such that if I encrypt a message with it and then lose first say 300 bits ...
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What are the misconceptions of IBM's CEO Arvind Krishna talk on the "Axios on HBO" about the quantum computing

IBM CEO Arvind made a talk in HBO's Axios program. It seems that there are misconceptions/misleading/flaws in reasoning etc. What are those! Some of the details of the speech is given as; IBM says ...
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What is reaction attack?

In the paper of "Reaction Attacks against Several Public-Key Cryptosystems" CiteSeerX link, reaction attack is defined informally as "Obtaining information about the private key or ...
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Encrypted data sharing in decentralised system

Alice encrypts file using her public key and upload it to decentralised file store (some service). Bob buys access to the file. Is it possible to share decrypted file with Bob without having Alice's ...
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What is/was SEC#1 ECC public key leading octet 0x01 for?

In the SEC#1 elliptic curve cryptography standard, the encoding of the public key involve a leading octet: 00h: The public key is the point at infinity. 02h, 03h: The public key is the compressed ...
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How to ensure the data comes from verified source without using asymetric encryption

I'm building a project that is remotely controlled using LoRa and I want to ensure, that nobody can imitate my transmitter and send packets to my receiver. Just encrypting sent data is not enough ...
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Question about white-box rsa algorithm

I found a scheme for white-box RSA. It seems to protect the input and output of modular operations. I'm curious about how to analyze the security of this solution. Does anybody know anything about it?
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Why is confusion and diffusion never talked about in asymmetric crypto?

While talking about symmetric encryption schemes like AES we always have a goal of achieving confusion and diffusion. But when it comes to asymmetric encryption schemes like RSA, DH etc. we never talk ...
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KP-ABE Key Generation

In Key Policy Attribute-based encryption if we need a targeted broadcast where the set of attributes are the same for a group of users. It means they all share the same secret key right? Or is it that ...
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Is Diffie-Hellman Key Exchange an Asymmetric or Symmetric Algorithm? [duplicate]

To my understanding, the DHKE algorithm is symmetric since it only produces a shared secret, rather than public and private keys, however googling "is diffie hellman asymmetric?" results in ...
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Why does Shamir's Trick for RSA Work

I have read that Shamir's trick can protect RSA with CRT against fault attacks. However, it is not clear to me why the following equations $$ s_{p}^{*}=m^{d \bmod \varphi(p \cdot t)} \bmod p \cdot t \\...
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Multiuser encryption, singleuser decryption [duplicate]

I have an hybrid encryption (RSA, AES) for a file sharing project I am working on, where I use a single public key for encryption on the sender side and corresponding private key for decryption on the ...
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ECDSA - generating a new private key each time we sign?

So, I kinda get the mathematics behind the ECDSA, but I can't seem to find precise information about private key generation. In other words, do we have to generate private key, each time we generate a ...
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Are all public key a result of computing g^k mod p

I just read through the text book definition of Diffie–Hellman key exchange. And from what i understand, the public key that is shared based on the protocol is calculated from: ...
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Revoke key without communication between the party who revoked it and the party who is validating

I received a very weird question from someone. I feel there is no solution, It would be great if you guys share your views. There are three people Alice, Bob and Sam and they all work for a high-...
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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 ...
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Understanding Practical Differences Between ElGamal and Diffie-Hellman

I've been tasked with building a Web Assembly site that implements E2EE. I was thinking of using ElGamal Encryption to encrypt the message and Diffie-Hellman to establish the key. After doing further ...
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How to decompose a public key into subgroups EC?

Is it possible to decompose the public key into its own subgroups? Suppose we know the order P with which the public key was generated ...
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How can we link AES with Elliptic Curve Diffie-Hellman Key Exchange Method

Actually, I am working on a project to combine symmetric and asymmetric cryptographic algorithms. The shared secret key for AES will be generated through the Elliptic Curve Diffie Hellman Key Exchange ...
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is there any good attack model of HMAC?

are there any good attack models of HMAC ? like how it can be attacked ? if there are any possible attacks of HMAC i would be happy to know about it.
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Generation of RSA key pair and storage of only private key PKCS#11

I noticed that the PKCS#11 supports C_GenerateKey function for symmetric keys and for asymmetric there's only C_GenerateKeyPair ...
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RSA key generation: why use lcm(p-1, q-1) instead of the totient ϕ(n)?

As far as I can see, generating a private key from two prime numbers p and q, having calculated ...
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Authentication of certificates

In order to provide authenticity of a sent message, we use certificates as fingerprints. But how do I know that the certificate is not stolen by someone? If the certificates are made public, why cant ...
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RSA implementation not working with large values for plaintext [duplicate]

While implementing RSA encryption/decryption (using python), the plaintext doesn't match with the decrypted ciphertext for large values of plaintext. Works fine for smaller values for plaintext (...
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Is this RSA-based IBE Scheme secure?

The PKG performs the following steps Choose $p,q \in \mathbb{P}$. Calculate $N=pq$. Calculate $\phi (n)=(p-1)(q-1)$. Choose $e$ with $gcd(e,\phi(n))=1$ and $1 < e < \phi(n)$. Let it be $e = {p^{...
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Is it possible to extract a signature from a HTTPS webpage?

Let's say I want to prove to someone that a webpage claims X. I could take a screenshot, but it could easily be doctored. However, the webpage's contents are encrypted by the domain using its private ...
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Proof that the encrypted content is the same as the promised original

Context : Alice has some content (C) and published its hash (Chash) publically. She wants to send C to Bob in a way it's visible only to Bob. This can be done by encrypting (Cenc) in using his Public ...
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Specific case of RSA where cipher text equals plain text

How did they arrive at the conclusion that there are 4 messages where plain text equals cipher text from "It is easy to show that in RSA, when e = 3 there are 4 messages m for which the ...
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Is there a way to do asymmetric cryptography where a single encrypted piece of data can be decrypted by multiple private keys?

Let's say you want to build a decentralized discord or slack. If there are two people involved, you could just have the public key of alice encrypting the data that bob sends so that it can be decoded ...
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Authentication in P2P networks without central server

I'm trying to understand how to perform authentication in an P2P network without a central server. Given a network with no central trusted unit and a PKI, how can one be sure of the authenticity of ...
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Is RSA the only current practical option for asymmetric encipherment of symmetric keys at rest?

As of 2021, is RSA the only practical (i.e. safe, production-ready) option for asymmetric encipherment of symmetric keys at rest? ECDSA is obviously preferable over RSA in the case of signing, but (...
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OpenSSL EC PRIVATE KEY content structure details

Background I am trying to understand how PEM contents are formatted for "EC Private Key" so e.g. following is private key ...
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Why is asked that gcd(pq,(p-1)(q-1))=1 in the Paillier encryption scheme?

I don't see this property $\gcd(p\,q,(p-1)(q-1))=1$ used in the scheme. And in Paillier's original paper, I don't find this requirement. Is it required just for the difficulty of factoring $n$? Or is ...
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Why RLWE is hard or even has a solution?

I was thinking about why and how the RLWE problem is hard at all. I know that it's hard because it can be reduced to the shortest vector problem, but I'm thinking about how does it even have a ...
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Is a RSA private key leak possible if I both sign and decrypt? [duplicate]

Is it possible to leak private key data if attacker control signing request ? Everyone know $N$ and $E$ because they are public. My server is designed to decrypt incoming request which is encrypted ...
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Can a PKE scheme be turned into a signature scheme?

Recently, I have been wondering whether you can turn any PKE scheme into a signature scheme and, if so, how (is there a general construction, or is this scheme-specific?). I have found several posts ...
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RSA impossible to be factorized?

If the RSA numbers are odd, how can they be factorized by two primes, since a prime is only divisible by itself and 1?
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Does CPA model the challenge plaintext are the same

For a CPA-secure encryption scheme, suppose that there is an adversary who can find that the two ciphertexts are encrypted from the same plaintext. Is this encryption scheme still CPA secure? Or, CPA ...
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Private Key from Extended Private Key and Public Address [closed]

Is it possible to generate a private key from a public address and an extended private key? For context: I am using C# and NBitcoin. The public address is generated from the outside via an extended ...
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How to find integer point of a ec curve in a given range?

I was looking inside the basics of ecc and found the examples from Internet either uses continuous domain curve or use a very small prime number p like 17 in a ...
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What is a good and bulletproof private key for ECC curves?

I am quite new to cryptography low-level mathematic details, though had worked in the crypto area for 2.5 years before. So if I am wrong about any of below part, please correct me without a facepalm ...
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User key management scheme: BYOK vs. client only keys vs. a mix of both

We are designing a web app where users can share documents with each other. The ultimate goal is to achieve zero trust needed by the users, i.e. client-side encryption makes sure that the servers (or ...

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