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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How to find d in the RSA algorithm?

Given N and e, and knowing that N^0.25 <d< N^0.5, how is it possible to find d, and with what time complexity?
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Will a semi-hyperelliptic pairing be used in real-world cryptography if it is faster than state-of-the-art elliptic pairings?

Let $\mathbb{G}_1$, $\mathbb{G}_2$, $\mathbb{G}_T$ stand for three groups of the same large prime order $r$. I invented a pairing $e\!: \mathbb{G}_1 \times \mathbb{G}_2 \to \mathbb{G}_T$ (with ...
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RSA with huge ciphertext

I am trying to find the flag from an RSA ciphertext, I am able to get the factors from factordb.com but the given e is not ...
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How to know that MAC isn't modified in ECIES

I am new to ECC but I was wondering, If there is a situation where instead of the ciphertext being falsified, the sent MAC was tampered. How does the receiver verify that the ciphertext is still ...
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Prove a plain text belongs to encrypted data

Given an encrypted (RSA) message and it's original plain text, is there a way to prove that the plain text belongs to the encrypted message ?
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padded RSA encryption: valid ciphertext from another

Considering padded RSA. Given an encrypted packet E(pubk, x) is It possible to generate a valid encryption E(pubk, x|y) without knowing the value x (but knowing only y)? For example merging in some ...
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Generating pairs of elliptic $\mathbb{F}_q$-curves isogenous over $\mathbb{F}_q$ such that nobody knows an $\mathbb{F}_q$-isogeny between them

Let $\mathbb{F}_q$ be a large finite field. What if I invent how to efficiently construct pairs of elliptic "cryptographically strong" $\mathbb{F}_q$-curves $E_1$, $E_2$ isogenous over $\...
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Are digital signatures unique for the messages they sign?

Practical implementations of digital signature algorithms (DSAs) employ hash functions to ensure that input is small and of a fixed sized; otherwise, DSAs would be too slow for most real-world ...
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Are RSA keypairs proof of work?

My computer generates a 65536-bit RSA keypair in 106 minutes. Is there a way to generate them faster by some trade-off? Can they be created in bulk, so long as they're able to encrypt and decrypt? Is ...
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Can a private key be reverse engineered when a 3rd party has a lot of my digital signatures? [duplicate]

I am wondering how secure it is to share digital signatures with a 3rd party (signed using one private key). For example, let's say I'm signing a million different messages with my private key and ...
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Is there any Cryptographic loop function that returns first input?

I want to use cryptographic function that returns the initial input or something related to it like its hash, the function should work like Encrypting some data or its hash, then encrypt the output of ...
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Proof that user compressed public key corresponds the curve equation (secp256k1)

I am trying to check if some compressed public key corresponds to an elliptic curve equation (secp256r1). As far as I know it should be valid once the following equation is fulfill y^2 = x^3 + ax + b ...
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Mitigation of lattice-based KEM decryption failure possibility

Lattice-based PQC KEM has small probability of decryption failure In an offline setting it can be catastrophic despite being improbable. Proposed mitigation: ...
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ECDSA | How to determine if a public key `y` value is positive or negative?

As we know every x value has two y values which are reversed. Just by having the public key, is there a way to determine which side the y value is? My first ...
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Can we change the content of an encrypted message without changing the public key?

A supplier is sending me very private information. For security, we are using thedecryptor.com website to encrypt the message. The website provides public and private keys. We agreed that he will ...
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Can I use content-derived deterministic encryption key with hybrid encryption?

My use case, making public-key encrypted backups, requires deterministic public-key authenticated encryption. I favour NaCl box, but the way it is generally used is probabilistic and it yields ...
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If I have enough examples of a private key's signature, can I discern it?

I understand that you can't discern a private key from a public key, but what if you have thousands of examples of the private key signatures, and you know what the message/cypher is? Basically, you ...
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Transforming a encryption of binary representation of a number to an encryption of vector representation

Suppose Alice chooses a number $n\in Z_q$ and decompose it to its binary representation $b_0,b_1,...,b_d$. Then Alice encrypts these bits (can be any encryption scheme). Is it possible for Bob (who ...
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how to sign a payload with existing private key [migrated]

I have an existing private key like "4FcPXsrv3cr2rD5PULq3LYBnjYHXqvdvnCrJje1A2kMoVyFZgK5RTSM8msmQNeirvDSaR9LhPeZVyaV69oLx1WLz" (changed for obvious reason). I want to use this to sign a ...
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What issues does the following Distributed Shamir Secret Sharing scheme have?

What (obvious) security issues does the following "onion" Distributed Shamir Secret Sharing scheme on a blockchain for the purpose of e-voting have? The blockchain in this context, is an ...
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Information Theoretic Security for Public Key Encryption

Do there exist information theoretic secure public key crypto-systems? Are they useful in any way, or are they just mathematical curiosities?
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What do you think of my plan to secure on-chain sensitive data using asymetric encryption?

I’m new to development using web3 technologies and I have a use case where I want to store private data about the user in the public blockchain Polygon. This data should be recorded to be tamper proof ...
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Whats a practical and safe encryption to use today? [duplicate]

I'm new to making applications that encrypt sensitive data and so don't know where to start. My question is what is a good encryption scheme that can be run in a good time for normal application and ...
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Correct definition of circular security - multiple encryptions of $sk$ allowed?

As I understand the definition, it's an extension of CPA security where the attacker can ask for an encryption of the secret key, using the public key. My question is - does the definition allow the ...
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Find factors of N given RSA public key (e, N) and private key (d) [duplicate]

I am having some problems solving the following problem: find factors of N given RSA public key (e, N) = (11, 459703599527) and private key d = 125373708962. I calculated k = ed - 1/ N = 3, and Φ(n) = ...
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How to break RSA when $q = e^{-1} \bmod p$?

This problem was posed during a recently ended contest. I am given a value for n and e. e = 65537. n is a 2048-bit number. p is a 1024-bit prime number. q is the modular inverse of e mod p. That's ...
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Does a list of discrete log equations reveal information?

Given public generator $g$ of some cyclic group, a secrets $x\in Z_q$, and public pairs $(a_1,b_1),...,(a_n,b_n)$ (where $a_1,...,a_n$ are selected at random from a big set), and prime p, that ...
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keyring encrypted with public keys

I would like to publicly store a list of public keys of recipients in a way that only the individual recipient ( who holds the private key of a that referenced public key) can see that he is ...
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Is it possible to prove that an encrypted message was encrypted with some public key without divulging the plaintext or secret key?

I know this seems a bit contrived, but I’m a layperson to cryptographic systems and have been trying to think if it’s possible to devise a scheme where it’s possible for a sender to prove, in a public ...
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How do you use a PQC Hybrid Shared Secret in Practice?

In https://tools.ietf.org/id/draft-stebila-tls-hybrid-design-03.html, they define (many other sources do too) hybrid shared key exchange as “Hybrid” key exchange, in this context, means the use of ...
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Is Regev’s public-key encryption with $sk$ chosen from $\{0, 1\}^n$ circular secure under CPA security?

I thought maybe this is true with something like the following reduction (if we assume for contradiction that it is not circular secure): For $A$ to 'break' CPA security, let $C$ be the 'collaborator' ...
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Can a user set his public key without knowing its corresponding private key? [closed]

I'm wondering if in public key infrastructure (PKI), a system user be able to set his public key without knowing its corresponding private key. Can this be done?
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Can functional encryption encrypt and decrypt negative integers?

I want to use DCR-based functional encryption for encryption and decryption purpose. However, I'm unsure whether DCR-based functional encryption can support negative integers. Is there any ...
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Can asymmetric encryption be used in HMAC, and still ensure the data has not been tampered with? [closed]

Suppose I want to send a message, but not privately; I want everybody to see it, even an attacker in the middle. I would do this by appending a public key to the start of the data, which could be used ...
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Do we want to allow/Have we allowed parallelization (e.g GPU programming) to enter the cryptographic field? What are the consequences?

With the term GPU programming, I'm referring to highly parallelizable computing in general. Lastly, I have built a bit of a background in cryptography. So I have started to wonder if/where GPU ...
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What happens if the Miller-Selfridge-Rabin-Test fails

MRT is a probabilistic test and even the deterministic version relies on the correctness of the Riemann hypothesis. When the test fails and I use a non-prime number in e.g a public key encryption ...
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Are Encryption, Key Exchanges and Digital Signature the application of asymmetric encryption

Reading the wikipedia entry on asymmetric cryptography, will I be wrong to conclude that there are 3 main broad category of application for asymmetric cryptography? Mainly: encryption digital ...
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Asymmetrical scheme: insecurity concerns of saving a hash of a hash of a password

please verify or explain how to do this properly. I'm letting a user create keys from the client through a secure server. I ask the user for a password on the client, then send the hashed password to ...
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Difference signature / asymmetric encryption (PQC)

The NIST is currently trying to select new standards for post-quantum cryptography. The two main categories for the candidates are "Public-key Encryption and Key-establishment Algorithms" ...
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In RSA, What does gcd(e,phi) != 1 means? Why always choose e = 2^n +1 not 2^n?

Recently I have few experiences with Questions in RSA which e is 2^n instead of 2^n+1, and that leads to gcd(e, phi) is not equal to 1... Won't this make the private key impossible to get? Is the ...
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Is it possible to calculate the modular inverse of a secp256k1 public key?

I know that it wouldn't be possible to use the extended Euclidean algorithm, since it would require the ability to divide a public key and calculate the remainder. I was wondering if there were any ...
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Security definition for IND-CPA of public key encryption

In the security game between the challenger and the adversary for the security definition of public key encryption, the challenger creates and gives the public key pk to the adversary. The adversary ...
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What does Euler's theorem have to do with RSA?

In RSA we compute e (encryption key) and d (decryption key) $\bmod phi(n)$ and not $\bmod n$, so how come when we get the keys and encrypt and decrypt we use $\bmod n$ not $\bmod phi(n)$ using the ...
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Signature delegation without secret keys

Scenario: have an entity A that cannot hold any secret keys. A concrete example would be: an application that needs to be open sourced and cannot be modified. In order to send any signed messages, it ...
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Paper that specifies how to define number ranges inside the ECC with varying equations

I am looking for a textbook or published paper that provides specific information on how to configure an ECC. I came across it several years ago and now cannot find it. Does anyone know the source? ...
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Does this encryption scheme have any major vulnerabilities?

Recently I asked a question of whether there is any cryptosystem that satisfies a number of properties (read the properties). Continuing to the promise I gave there, this is my attempt to construct it....
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Is there a public-key, "deal-less", all-or-nothing, "secret-length message" cryptosystem or some easy way to derive it?

I want to make an ecryption algorithm that is secure in, well, really many ways, which is hard I see, so I came up with some ideas of how to implement it using some primitives that I know and I ...
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Why do we need to use Asymmetric cryptography if Diffie-Hellman solves the key exchange problem of symmetric cryptography?

I am new to cryptography and I cant get my head around this issue: If symmetric cryptography is faster then asymmetric and given that Diffie-Hellman key exchange algorithm allows you to exchange keys ...
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Is there a discrete log challenge?

RSA challenge is well-known and it has a wiki page. Is there a discrete log for $\mathbb F_p$ where $p$ is Sophie-Germain prime?
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Is possible to cipher a 64bit message into a 64bit message using public key cryptography?

I'm looking for a non-invertible bijective function mapping a 64bit value into another 64bit value. I can't use a hash because it isn't bijective. Could this be done with public key cryptography ? The ...
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