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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Three Pass Protocol Question!

Alice and Bob have agreed to use the Three Pass Protocol. p=1009 Alice chooses the encryption exponent e_A = 101 Bob chooses the encryption exponent e_B = 209 Now Alice and Bob send three ...
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XTZ Private Key

The BIP39/44 off-line tool does not contain XTZ coin. Therefore, I cannot derive (from my 24 words) my ledger nano s private key associated with my Public key for my Tezos account. Is there another ...
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Are there any algorithms for which generating any zero-knowledge proofs is not practical?

It is related to my earlier question: Can zkSNARK or other zero-knowledge proofs be used to proof message authenticity without revealing private key? Are there any algorithms for which generating ...
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Secure multi-party computation for digital signature

Is there any practical algorithm that will allow to use public key cryptography (RSA or ECC) in the following way There are N parties. Up to M are malicious adversaries (were trusted, but got taken ...
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Can zkSNARK or other zero-knowledge proofs be used to proof message authenticity without revealing private key?

The situation: Alice and Bob are exchanging messages encrypted by some known asymmetric encryption protocol. All their encrypted messages, as well as public keys are intercepted by Charlie. Can ...
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Factorization problem

Say, $X= a\cdot b$, where $(a, b) \in Z_q^*$ and $q$ is a large prime. If $X$ is given, then what is the complexity (or hardness) of finding $a$ and $b$? Note that, either $a$ or $b$ can be reused to ...
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Why can't ransomware practically use RSA to encrypt all files?

I understand that a few ransomware have used an RSA public key to encrypt all files belonging to the victim. This is a bullet-proof system in terms of its security because the private key is always ...
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understanding LWE public key algorithm

I'm trying to understand this LWE public key system say I use matrix A = [[44, 73, 20, 54],[92, 19, 78, 22],[31, 34, 94, 29],[82, 32, 70, 68]] q = 97 bit = 1 and secret key s: [56, 90, 0, 46] and ...
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Advantages of encrypting a symmetric key with a public key vs using a fixed symmetric key

I am new to cryptography concepts. I am trying to protect some firmware download. Reading some Wikipedia pages, I understand that asymmetric cryptography is time consuming, so, if I want to protect ...
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Non-derivable public key asymmetrical encryption? [duplicate]

The need we have is to pass encrypted messages but such that the encryption key can't be generated from the decryption key. This sounds like with vanilla asymmetrical crypto I know, but in every ...
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Same ephemeral key for 2 uses

I am theorising an onion routing network, and I have a question about ephemeral keys. This is the basics e2e connection encryption protocol. ...
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Multiple sender single receiver Encryption

I had this article given to me by my teacher, and I would like to enhance it. It's titled Modified El Gamal Algorithm for Multiple Senders and Single Receiver Encryption. I planned on having the ...
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Forward Security of Symmetric Encryption Schemes with LFSR based PRNG

Forward security can be achieved using symmetric encryption schemes by combining with a pseudo-random number generator (PRNG). Does LFSR based PRNG provide forward security in this case?
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How are precision and security related in a Gaussian Noise Sampler for R-LWE?

My understanding is that the sampling precision in Gaussian Noise sampler is related to security. But not sure about why is that? I read that when the samples are floating-point numbers and precision ...
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How does the key agreement process take place in Virgil E3Kit SDK for end to end encryption?

I'm using Virgil E3Kit SDK to implement end-to-end encryption in my App. Their E3Kit SDK is very effective and not too hard to understand, but I still don't understand how does the key agreement ...
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Is 128-bit security still considered strong in 2020, within the context of both ECC Asym & Sym ciphers

Given that much of our ECC crypto primitives provide “only” 128-bit security when defined over a 256-bit curve due to pollard-rho, is it then still safe in 2020 to consider 128-bit security safe for ...
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Risks with OpenSSL verifying a signature with un-trusted PEM encoded public key [migrated]

If a website user wants to use WebAuthn, they will start by creating a credential, where their authentication device provides a public key. This key is encoded, and sent back to the server to store ...
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Diffie-Hellman Key Exchange with Authentication: Man-in-the-Middle query

I have been reading up on MiTM attacks, and the prevention of them using public key certificates. Recently I learnt about Diffie-Hellman Key Exchange with Authentication, and how it uses signed ...
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Derived keys usable by threshold signatures

Suppose there are $n$ members in a $(t,n)$ threshold signature scheme. The global secret key $sk$ is not known to any single party, as the keys are generated distributed. The parties are able to ...
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Creating nested messages in OpenPGP

I need to create a nested message in OpenPGP (my understanding is that the protocol itself should support it). Let's say I have Payload ("Time in Lordran is ...
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Help with cryptanalysis of branching in schemes based on Multivariate Public Key Cryptography

I'm familiarized with the structure of branching found in Multivariate Cryptography, as it allows us to partition a $n$-tuple over $F_{q}$ into a $k$-tuple where the $i$-th element is in $F_{q^{\...
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Is there any encryption system where the sender cannot prove that a specific ciphertext belongs to a specific plaintext

I'm trying to create a message-transfer system where The encrypted messages are stored in a public database. It is possible to verify who is the sender of this message. The sender cannot prove to ...
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Is it possible to generate a membership proof using an RSA accumulator without knowing all the accumulated values?

I am currently learning about RSA accumulators and this was just a question I had since in most available implementations I see in Github accumulated primes are stored in hash tables and they are ...
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Doesn't d6 to binary for 256-bit bitcoin private key generation produce biased results?

If the mapping table looks like: 1: 000 2: 001 3: 010 4: 011 5: 100 6: 101 Then you are guaranteed that your key will never have a chain of 4 or more 1s, much fewer chains of 3 ones than would ...
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What's the difference between threshold signatures and multisignatures?

I was wondering what's the difference between threshold signatures and multisignatures. In what respects do they differ? For example, is n-out-of-n threshold signature, just a multisignature?
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Lifting point to quadratic twisted curve

How to lift point to it’s quadratic twisted curve? I use secp256k1. Is the diiscrete log still same? Thanks before
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Using ECDSA keys for encryption

I know that ECDSA is used for signature only, but I wonder if I can use the public/private Elliptic Curve keys for encryption too. I have ECDSA SSH public keys and I wonder if I can use them to ...
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How can I make a new public cryptosystem using given public and private key cryptosystem?

Given a Public key cryptosystem with (Gen1, Enc1, Dec1) and Private key cryptosystem with (Gen2, Enc2, Dec2) I want to construct a new Public key cryptosystem (Gen3, Enc3, Dec3)?
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Key Exchange vs Key Encapsulation

From what I understand, the steps of a key exchange protocol are Alice and Bob each encrypt something using their public key and private key and send the result to each other Alice and Bob each do ...
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ECC encryption in practice

I'd like to encrypt a message using PGP keys, and elliptic curve cryptography as the method. In practice, using the Erlang :crypto module, but first, I'd like to ...
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How to generate a public key from a private ECDSA key?

Having some specific ECDSA curve and a private key, how does one calculate the public key? I am having a hard time finding the algorithm and equations for it.
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Keeping a backup of asymmetric keys with the help of a certificate authority without losing the privacy

First I'll explain the problem, then I will also give a solution(it might be wrong) I've found for it, you let me know what you think about this solution and whether you have a better one. Assume a ...
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Proof possession of private key in libsodium

I would like to proof that I am in possession of private key sk for public key pk using ...
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Relying on a private public key for authentication

I'm Alice, and I generate a public/private key pair. I securely & confidentially share my public key with Bob and Carol, who securely & confidentially share it with various other benevolent ...
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Computing PGP ed25519 and curve25519 keygrips?

There are public key algorithmic differences for how PGP computes fingerprints and keygrips. For the v4 protocol, fingerprints are not exclusively computed from public keys while keygrips are. RFC ...
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Can Paillier ,RSA or any other schemes be used for universal re-encryption like elGamal?

ElGamal, RSA, and Paillier cryptosystem have homomorphic property, and can be used fro re-encryption purposes. I want to use the encryption to re-encrypt ciphertext(as in proxy re-encryption but ...
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How to design a moderated, group for private messages?

I’m trying to figure out how I could create a private group that was P2P yet still allowed someone to moderate members (no public access to messages). I’m assuming standard hybrid encryption (RSA/EC + ...
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405 views

How trivial is it to derive a private key from two public keys?

It turns out that what I was attempting to do was create a form of ECDSA threshold signature protocol by just giving away multiple public keys and then having the two parties solve for the private. ...
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Using Permutation polynomial to compute a MAC

Is the following MAC secure? For a block $y_i$ in a file, we defined a MAC as follows: $Mac_i:PRF(k,i) \cdot g^{y_i \cdot r_i} \bmod p$. Where $p$ is a prime number, $g \in \mathbb{G}$,$PRF(k,i)$ is ...
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Negotiate a secure connection without certificates?

I would like to have a simple experience for a user for setting up a secure connection between two computers against a MITM attack. Something like the following: A number (possibly base64) appears ...
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After ECDH with Curve25519, is it pointless to use anything stronger than AES-128?

Is the following reasoning correct: After ECDH with Curve25519, the resulting shared secret will be an EC public key with a bit strength of 128 bits. This public key would then be hashed (let's say ...
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Difference between Verification and Public Key for Signature Schemes

This is a semantics Question. Typically, in many asymmetric schemes, for this question specifically, digital signatures, we see that designers describe the key given to the verifier as Public Key. ...
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Is there a library that implements the “Mickey Mouse Version” of asymmetric cryptography?

Here is what I mean with "Mickey Mouse Version": CHARLIE makes a keypair key1 and key2 ...
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Cryptographic equivalent of family coat of arms

As a layman when it comes to cryptography, I have recently been asking myself if there was a cryptographic equivalent of a family code of arms. I'm thinking of something asymmetric, that is future ...
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two public keys with same passphrase insecure? | can two hashes be compared?

Suppose someone had generated a 2.048-Bit RSA GPG/PGP key pair and published the public key on the usual key servers. Then he withdraws this key and generates a new one in 4.096-Bit RSA using the same ...
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Asymmetric non-interactive proof of work scheme

I'm looking for a non-interactive proof of work scheme. I want for it to (1) be faster to find solutions to if you're in the possession of an arbitrary secret, like a private key, and (2) for the ...
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Why is recipient hashed in this Sign/Encrypt/Sign proposal?

Own research In my journey into trying to understand PGP, and public key signing and encryption as a whole, I came across this answer on CE. It is an answer to a question with the title: Should we ...
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Large Volumes of Asymmetric Encryption

First of all, I apologize in advance if I use any incorrect terminology. I am just getting my feet wet when it comes to cryptography and there is a lot to learn. For the past 12 months, we have been ...
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ECC public key encryption without symmetric cipher

Imagine the following scenario. A process is running in background and permanently encrypting some data. An adversary has full control of the process, e.g. it can dump the process memory any time and ...
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End to end encrypted web chat app with stored messages in database

I am working on a web app with an integrated chat. All chats can only occur between two users - not more, not less. I am very concerned with security, so I would like to encrypt all chat messages with ...

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