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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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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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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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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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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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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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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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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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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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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Secure implementation of public key cryptography

Reading online I've found out that for example the RSA implementation that you usually find on textook is not secure. Where I can find some secure implementation of algorithm such as RSA, ECDH, ECDSA? ...
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Assistance with parsing PGP PRIVATE KEY BLOCK's Secret-Key Packet (0x6) and Secret-Subkey Packet (0x7) using command lines and RFC 4880?

The throw away private keys below (master ed25519 & subkey curve 25519) were exported without being password encrypted. % cat skaht_0523F5B4_Secret.asc ...
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Using RSA public key as private key and vice-versa

I am writing an application that involves checking to see if data has been created by me. I do this by encrypting the data with the private key on my server, and then decrypting it using the public ...
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Define a Decryption algorithm on a given group-based Cramer Shoup lite scheme

I am currently working on public key encryption schemes and I want some help to figure out how decryption algorithms work. Suppose we have a public key $pk = (G,p,g,e)$ with $e \in Z^*_p$ . (where $G$ ...
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I need two types of easily crackable asymmetric and symmetric encryption

I have a school project in which I'm comparing asymmetric and symmetric encryption. I need two different types of easily crackable encryption, one symmetric and one asymmetric. I am planning on ...
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Multiple (RSA) public key encryption how to verify others received the same information? Non-deterministic encryption

I have an RSA system between multiple parties. Alice takes the targets (Bob and Oliver) public keys and encrypts a message using them and sends it to them. All parties know each other's public keys ...
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Who verifies the trust of certificate authorities?

Background I am a novice in the field of cryptography and cyber-security, and while studying asymmetric-key encryption, I learned about the potential of a man-in-the-middle attack. To mitigate this ...
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The goal, the method, and the interface of the signcrypt primitive.

Some time ago, I proposed making the site more educational by teaching correct cryptographic programming. The proposal had had somewhat good reception, but was met with cold ice as there had been ...
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Is there a LWE based public-key encryption scheme which is CCA1-secure?

Is there a lattice based PKE which is IND-CCA1 secure? Actually I am only familiar with LWE and SIS. So I want to know that what the IND-CCA1-secure LWE based PKE scheme looks like?
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Benefits of signing RSA-encrypted data?

I recently came across this (PDF) journal article, which describes what it calls "A New Design Of A Hybrid Encryption Algorithm" (which I must say, doesn't sound very novel, even in 2014!): An AES ...
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Brute forcing an elliptic curve encrypted key

I've been reading about ECC, and what I've established so far (correct me if I'm wrong) is that: pubKey = privKey * G where G is some special point on the secp256k1 curve. Doesn't this mean we ...
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Is it possible to multiplex TLS connections by SNI metadata without knowing any keys?

Imagine the following communication diagram: C1-----\ /--B1 C2------P---B2 ...----/ \--... We have multiple C(lients), call them C1, C2, etc. They connect to a ...
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Is it possible in PGP to provide verification/verify the ownership of a public key?

I am new to PGP/GPG and I am somewhat confused by the idea of the Web of Trust (WoT). Isn't signing a public key with its private key enough to prove the ownership of it? if it is so, why don't key ...
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Generalized Benaloh cryptosystem with $r=2$

Benaloh cryptosystem requires $\gcd(r, (q-1))=1$ which is impossible if $q>2$ (since it needs to be a large prime) and $r=2$. This confuses me, since Benaloh is referred to as an "extension" or "...
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Verbatim of early work on public-key cryptography?

In late 1997, the history of public-key cryptography was turned around with the announcement (then extended) that public-key cryptography was theorized in a 1970 note [1] by James Henry Ellis: The ...
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Verifying the ownership of curve25519 public keys

Let's say we have a group of users, authenticated by a server that providers the service, communicating on a secure channel (e.g. over HTTPS/TLS) and each user has a corresponding curve25519 key pair. ...
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Is the first Nonce exchange between Alice and Bob in Needham-Schroder key exchange protocol redundant?

For the Needham-Schroder protocol, assuming Alice and Bob are both able to guarantee each other's public keys (e.g. through a Certificate authority), the protocol is 1) A sends to B: $E_{publicB} [...

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