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 does FORS: Forest of Random Subsets work?

I saw a post named "How does signing with FORS work in SPHINCS+?" but in the post it seems like no one had explain how does the FORS works. SK: Secret Key, PRF: Pseudo-Random Function I'm ...
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Is gcd(e,p−1)=1=gcd(e,q−1) similar to gcd(e,phi(n))=1?

I wonder, is $\gcd(e,p−1)=1=\gcd(e,q−1)$ similar to $\gcd(e,\phi(n))=1$ ??
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All 32 bit primes on 1 640Mb CD-ROM , and then used as immediate lookup of resulting prime factors, is that even possible, in early 1990s? [closed]

I was having a conversation with a private key cryptologist who claimed they created and distributed, in the early 1990s, all 32 bit primes on 1 640Mb CD-ROM, which could also used for immediate ...
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RSA/ ECC keygen HW vs SW

i have a pretty straightforward question but i can’t seem to find an answer : Regardless of the physical protection provided by an HSM or TPM or any hardware cryptographic key storage system, are keys ...
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In RSA Encryption, Can I choose the public exponent e > m (modulus) ? or e > φ(n)? [duplicate]

In RSA ,the encryption, Can we choose the public exponent (e) greater than m (modulus) or e > φ(n) ? I wonder about choosing public key exponents (e) because the most information on the internet or ...
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Hybrid key exchange in TLS 1.3

In Hybrid key exchange in TLS 1.3, they mention that with a hybrid approach, we concatenate the shared secret from each method (say KEM like Kyber768 + classical ECDH X25519 = X22519Kyer768). ...
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Is using a CPA secure public key encryption twice on two halves of the message with different keys secure?

If $\Pi=(\mathrm{Gen},\mathrm{Enc},\mathrm{Dec})$ is a CPA secure public key encryption protocol, is the following public key encryption CPA secure? $\Pi'$: $\mathrm{Gen'}$: Run $\mathrm{Gen}$ twice ...
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In RSA Encryption, Can the public exponent e > m (modulus) ? and can we choose any public key without paying attention to the conditions? [duplicate]

In RSA ,the encryption, Can we choose the public exponent (e) greater than m (modulus) or e > φ(n) ? I wonder about choosing public key exponents (e) because the most information on the internet or ...
Nicha59's user avatar
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Does higher key sizes correspond to a higher security parameter?

If a system provide n bits of security, it is known that the best possible attack against the system would be 2^n (security parameter). However, why are the key sizes of some cryptosystems much larger ...
rin ichinose's user avatar
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Double- and -add algorithm

I am currently doing the elliptic curves and I'm stuck for 8 hours without finding solutions. I under stand the process of double and add but don't know how to obtain 5 * 8P = 4OP =11 P. 11 P was in ...
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A matching X25519 public from non-clamped Ed25519-public and Ed25519-secret

Given an Ed25519 key pair, can you think of any way to get to the same X25519 public key from the Ed25519 secret as from the non-clamped(!) Ed25519 public key? ...
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Using asymmetric encryption + key rotation, is it possible to make an extra obfuscation layer?

I'm building a service, that works as the cipher and decipher for instant messages. It works by following the following steps: The sender encrypts the text(not long, mostly chatting messages) using a ...
DingoStiglitz's user avatar
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Is this ECDSA's protection mechanism or something wrong with it?

Over the past few months, I have been reading and trying to understand how ECDSA works and how safe is it. So now something does not add up between its signature verification and generation. But maybe ...
Alexio puk2sefu's user avatar
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Cryptography to tackle deepfake, proving the photo is original

Deepfake technology has become very difficult to tackle due to sophisticated machine learning algorithms. Now, even when a journalist or bystander provides photo or video evidence, the culprit denies ...
Amiya Behera's user avatar
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What is the purpose of $k \in \{2, \dots, p-2\}$ in ElGamal signatures on ${\mathbb{Z_{p}^{*}}}$?

The question is mainly stated in the title. I had to do a refreshment on public key cryptography. The algorithms are pretty straightforward however, I always stumbled upon this question. Is it in ...
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Best cryptographic method to distribute license files

I will describe my problem high-level, and not ask a very specific cryptographic question, since I am open for general suggestions as well. So in my question I will only speak about "security ...
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Can attackers see the values I pass on to OpenSSL API functions?

Respected community, I am using the OpenSSL API's, especially libcrypto and libssl and I am really depressed, thinking about ...
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in NTRU, can g be recovered given f and h?

The NTRU key generation involves polynomials and their arithmetic in polynomial rings, which is a bit different from arithmetic in modular integers. In the NTRU cryptosystem, the public key $h$ is ...
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Can the public key be derived from the private key? [closed]

The calculation/formula i use in deriving a public key from the private key without importing any module in python3 script involves the following steps: Define the parameters of the secp256k1 ...
Victor maith's user avatar
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How to calculate key length in bits?

On a technical forum discussion, an example key of 16 hexadecimal numbers was said to be 2048 bits in length. I do not understand this as each number would be 4 bytes - 32 bits - therefore to me 16 ...
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Benaloh cryptosystem

I was reading this article on Wikipedia, but I don't seem to understand how this holds: $u^\phi \equiv u^0 \mod n$. Can someone explain it to me? Thank you. Key Generation Given block size $r$, a ...
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RSA random key generation [duplicate]

How RSA keys are tested for primality if they are random generated? I imagine this could be time consuming task.
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How to determine the prefix of a SECP256K1 compressed public key

I need to store a public key in a variable of maximum 32 bytes. I recover the compressed key and remove its prefix, but then I have to do the opposite: I have to rebuild the compressed address from it ...
Sino's user avatar
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Efficiently detect that a ciphertext is meant for Alice

Assume we have the situation that Alice is receiving somewhere in the magnitude of 1_000_000 encrypted messages, whereby a small number (n<100 for 99% of cases) of these messages are meant for her. ...
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Zero-Knowledge Proof of Encryption with a Specific Key

Short version: Given a hash of a plaintext, a public key, and a ciphertext (but not knowing the original plaintext), is there any way to verify that the ciphertext is the plaintext after being ...
Jordan's user avatar
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Public key encryption with a large number of users

I'm building an app that will primarily be iOS or Android based. My plan is for every user to have their own key pair. The public key will be stored on the server along with a 128 bit UUID which is ...
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Use secp384r1 PEM key to sign a Verifiable Credential with Linked Data proofs

Ok, let me preface this by clarifying that I am not a cryptographer by trade, but I've been using cryptographic suites in the context of signing w3c Verifiable Credentials, and I am not sure if this ...
Moustachiste's user avatar
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Density in terms of knapsack public-key cryptosystems

I am quite new to knapsack cryptosystems (specifically the merkle-hellman cryptosystem) and don't quite understand what exactly is the density $d(a) = \frac{n}{\log_2max_i a_i}$ defined here among ...
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Security notion for asymmetric encryption when used in oblivious transfer

This paper suggests the following approach to oblivious transfer (OT), using asymmetric encryption: Receiver generates keypair $(pk_b, sk)$, selects random $t$, and set $pk_{1 - b} = pk_b \oplus \...
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Deriving $y$-coordinate

Is there any formula for deriving the $y$-coordinate using the $x$-coordinate and the slope in the secp256k1 elliptic curve? For example: Calculate the slope: ...
Aviril Smith's user avatar
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Constantly changing encryption for transferring data

I had an idea for safely transmitting sensitive data online, and I wanted an expert opinion. Would it be safe to encrypt data (for simplicity at this point just use plain text) with a ruleset (an ...
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Determining the order of operations in elliptic curve cryptography: Point doubling vs point addition for obtaining x and y values of a public key

I have a question regarding the operations performed on an elliptic curve, specifically related to point doubling and point addition. I am trying to understand whether it is possible to determine the ...
Aviril Smith's user avatar
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is it possible to calculate the difference between 2 public keys of secp256k1

I am inquiring about the feasibility of calculating the point difference between two distinct secp256k1 elliptic curve points. Given the nature of secp256k1, which is widely used in cryptographic ...
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Is it safe to create a public ID by hashing a private key?

In an application, a curve25519 private key is the only stable identifier for an individual. I don't have readily have access to the corresponding public key. Would it be safe to generate a public ...
Moss Richardson's user avatar
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Implementation of Ring Signature

I have implemented a ring signature in a Python program, To keep it simple, I have Alice and Bob. Based on this ring equation: $$ v = E_k(y_s⊕E_k(y_i⊕v))$$ I will get: $$ y_s = E_k^{-1}(v)⊕E_k(y_i⊕v) \...
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Why does OpenSSL RSA signing process need the public exponent?

I am trying to fully separate RSA key pairs by breaking down $(N,e)$ for public part and $(N,d)$ for private part. From my understanding of RSA signature process, the message to be signed is digested ...
KennnyCZ's user avatar
4 votes
1 answer
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What does the "static" assumption mean?

We can prove the security of a cryptographic scheme in standard model and non-standard model. Standard models like using some computational assumptions, on the other hand, non-standard models like ...
user1035648's user avatar
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Does using only one sign of secp256k1 publc keys weaken security?

As far as I understand, compressed public keys of secp256k1 can represent points either above or below the X axis, depending on whether they begin 0x02 or 0x03. Am I correct in thinking that if you ...
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Kleopatra: What is the strongest and most popular cryptography standard for PGP

While setting up PGP for the first time, I am presented with various encryption standards I can use being: RSA (2048, 3072, 4096 bits) with an option for + RSA (2048, 3072, 4096 bits) DSA (2048 bits) ...
Bill Joe's user avatar
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Which one is more general, attribute based encryption or inner product predicate encryption?

If we have a scheme for inner product predicate encryption (IPPE), then can we claim that we already have designed an attribute based encryption (ABE) scheme; So we do not need to design an ABE again. ...
user1035648's user avatar
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How brittle is the current public key encryption infrastructure

Edit: One half of the answer to this question also applies to a recently asked and now deleted question regarding the impact of an algorithm which breaks DLP over integers but has no impact on ...
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js-ethereum-cryptography secp256k1 signature difficulties

I'm currently undertaking a course on Blockchain cryptography. And our first project is to transfer tokens from one wallet to another using client / server application. All mock of course. This ...
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Changing the keys of an encrypted backup file

I have a series of backup files which are being generated daily and which I need to store encrypted. The files are to be used by bob as and when they need it. I am planning to use public key ...
Xuo Guoto's user avatar
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Transportation Key (KEK)

I was studying about how to transport keys from one HSM environment to another and it came to me that I would need some sort of transportation key so the HSM keys would be double encrypted. How would ...
Allan Romanato's user avatar
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Trouble detecting cyclic group order crossovers in SECP256K1

There's a problem in detecting whether the sum of public key addition has crossed the cyclic group order boundary For this example, think of public keys $Pub$ as private keys $Priv$, (private scalars),...
Maltoon Yezi's user avatar
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Functional Encryption in Private-key setting vs. Public-key setting

$\bullet$ What does private-key functional encryption mean? Or functional encryption in private-key setting? Wasn't functional encryption a generalization of public key encryption? So now, why do we ...
user1035648's user avatar
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Can we recover public key from DSA signatures as we can from ECDSA?

I learned the Public Key Recovery algorithm for ECDSA, and wonder if we can use it in DSA. The answer seems to be no, but details are welcome.
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Bandwidth-Efficient Non-Repudiation

I'm working on a project that involves broadcast (uni-directional) streaming and requires non-repudiation. Essentially, a device broadcasts a data stream over the air, and any receiving station needs ...
Jordan's user avatar
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Regev's learning with error

If we talk about the security of public key encryption in Regev's lwe system, if attacker would have knowledge of $(u,u'):[\mathbf u=A\mathbf r, \mathbf u'=\mathbf b^t\mathbf r + \mu q/2, \mathbf r\in\...
user479610's user avatar
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Does CCA security require rejection?

It seems like every CCA-secure KEM1 has some sort of check that the decapsulator performs. Sometimes failure will result in rejection ("explicit rejection") or the decapsulator will simply ...
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