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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Clarifying terms for cipher, algorithm, rsa, asymmetric, openssl

I am a self taught front-end developer and I am just trying to get my cryptography terminologies straight. I will make some statements. Can someone correct my mistakes? Question 1 I read that cipher ...
learningtech's user avatar
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Devising a system that allows for aggregate computations but does not hold the single values

First of all apologies if this is not the right place. I am not very knowledgeable in cryptography but I thought you can at least point me in the right direction of research. The following is a toy ...
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The weakening of PQC as a result of lack of KEX?

As far as I can tell we don't have any good key exchange post-quantum candidates. SIKE was broken some time ago. It is possible to reach an authenticated shared secret by having the public key holder ...
Squoomsquoom's user avatar
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In Bitcoin, given half the 52-character private key in WIF format, is it possible to reconstruct the whole private key?

Given the following two preconditions: It is almost impossible to reconstruct a bitcoin private key if an attacker only has one half of the private key as well as the public key. It is almost ...
Ohumeronen's user avatar
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P256 signature verification was succeed with 2 public key [duplicate]

I tried to recover public key from P256 signature. With 2 recovery id ( 0, 1 ), signature makes 2 public key. And I tried to verify signature with public key and verification was succeed all of 2 keys....
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Not understanding elliptic curve scalar multiplication to produce Ethereum address

This is the equation Public key = Private key * G Here, ...
Asif Iqbal's user avatar
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How does the security of RSA compare to a symmetric cipher when both public and private keys are secret?

When RSA is used in a fashion where both the private key and the public key are both secret (for example, when the public key in a KEM is never leaked) could RSA be then evaluated as a symmetric ...
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Given and encrypted message, is it theoretically possible to decrypt a message without the key or guessing it? If so, what methods could be used?

Decrypting an AES-Encrypted Message Without the Key: A Cryptographic Challenge Summary: I am investigating the possibility of decrypting an AES-encrypted message when the encryption key is unknown ...
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Keygen with timelock encryption so that the secret key is hidden from everyone?

I'm wondering if the following scheme (or something similar) can exist: I want to encrypt a randomly generate a public key and secret key pair, $(pk, sk)$. I would like that $sk$ is encrypted some ...
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In Symmetric encryption where Alice and Bob message each other, how can both decrypt the same data?

I first posted this question on StackOverflow but they told me it belongs here instead: https://stackoverflow.com/questions/77856486/in-symmetric-encryption-where-alice-and-bob-message-each-other-how-...
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RSA signatures without padding by using XOF output in range [1, n-1]

RSA signatures are implemented by encrypting the padded hash with the private key. Why not take the approach RSA-KEM is using by removing the padding entirely and replacing the hash with a XOF that ...
Jackie Lanhorn's user avatar
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Semantically secure public-key encryption scheme

Suppose that $(\mathrm{Gen},\mathrm{Dec},\mathrm{Enc})$ is a semantically secure public-key encryption scheme. I define $E' = (E(e,m)\oplus m)\parallel (E(e,m)\oplus e)$. Clearly, this is now not ...
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Ephemeral ECC refresh vs. simple hash ratchet

Some protocols employ ephemeral ECC key exchanges throughout the session. Such as the Noise framework. Is the rationale to do this simply because you can do it efficiently? To provide future secrecy ...
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Loop back or cyclic nature of secp256k1 curve

I am working with point addition and scalar multiplication on the secp256k1 curve for points $(x,y)$ or public keys to derive the next public key scalar k times further from it. Actually when I use a ...
Aflatoon's user avatar
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Are RSA signatures distinguishable from random data?

In the spirit of Are curve secp256k1 ECDSA signatures distinguishable from random data? Are RSA signatures distinguishable from random data? What if you don't know the message? What if you have many ...
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Security proof of this paper(Ciphertext-Policy Attribute-Based Encryption) which proposes the first CP-ABE scheme

I have trouble in understanding the security proof of this paper(Ciphertext-Policy Attribute-Based Encryption) why are these two hybrids equivalent to the modified game above? It is obvious that $...
WF Huang's user avatar
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Compute a proof for a verifiable delay function

I am trying to solve the following problem: Alice generates a RSA key $(n, \phi)$, she shares with Bob the value $n$, and $y = g^{2^{t}}\;\text{mod}\; n$ for $g$ a generator of the group $\left(\...
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Non-prime value chosen for u in DGK encryption

In DGK encryption, one of the parameters of public key is value u where it is a small prime with minimum length l+2. It is not obvious for me what is the security compromise if u is not prime. Any ...
Fattaneh's user avatar
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CCA security problem

Let $(\mathsf{Gen}, E, D)$ be a CCA-secure public key encryption system with a message space $\{0,1\}^{128}$. Is the following derived cipher $(\mathsf{Gen}, E', D')$ also CCA-secure? Justify your ...
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Finding plain text given two cypher texts of the same plain text with two diffrent public keys

I want to find the plain text from two cyphertexts of RSA, encrypted with two diffrent public keys. I know that: for E((n,e),m) = c0 and E((n,f),m) = c1 , c0^x . c1^y mod n = m mod n = m (ex + fy=1) ...
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RSA key generation with large random numbers and no primality testing

Does the security of RSA rest entirely on the modulus having at least 2 large random primes? Suppose you were to generate 2 random 1,000,000-bit numbers and just use the product of those as the ...
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Difference between a a doubled point and a point from point addition

Are all doubled points on an elliptic curve even, meaning if you compress the point, it will have '02' plus the $x$ coordinate? If not, what distinguishes a doubled point from a point resulting from ...
Dev Tenji's user avatar
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Cannot get RSA encrypt and decrypt to work in hardware and online calculator

I am attempting to get a hardware implementation of RSA working but I am having trouble with encryption and decryption. First, I ran these commands to generate the keys: openssl genrsa -out private-...
Jordan Krim's user avatar
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Possible to encrypt message without knowing recipient public key?

Assume Bob is sender and Alice is future recipient. In ideal situation Bob know Alice public key, and encrypt message with it. But what if Bob don't know Alice public key (he only will know Alice ...
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which DH protocol is safer in communication with given condition?

I am trying to understand some concepts such as DH problem and its variants. I have the following question from the book I read. (note that I translated the question from my language to english) ...
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5 votes
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Integrating Elligator mapping with libsodium Curve25519 implementation

I'm currently working on a project where I want to map Curve25519 public keys to uniformly random noise. The main idea is that when these transformed public keys are sent over a network, an outsider ...
Safari1811's user avatar
1 vote
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What scheme is the best for combining two shared secrets?

I'm developing a program that uses a hybrid Key Encapsulation Mechanism (KEM) scheme, employing Kyber and X25519, with each producing a 32-byte shared secret. What would be the best scheme to combine ...
Zola Gonano's user avatar
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What happens if we know that for an RSA key pair, the equation $d^e \equiv c \pmod{n}$ holds?

If we possess the knowledge that the expression $d^e \equiv c \pmod{n}$ holds for an RSA key pair, what would be the implication or consequence of this? Here, $e$, $n$, and $d$ represent the public ...
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Is it safe to derive a secret from a signature?

Many blockchain users have wallets that hold a private key, which can interact with a website. For example, the website can request the wallet to sign a specific message. 'Do only sign this message if ...
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I'm wondering if using the same one public key does not guarantee privacy in the computation of multiple data owners

Participating entity: multiple data owners, computing clouds Protocol: The multiple data owners send their data to the computing clouds, which perform the computation of the data. Privacy protection:...
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Are high-dimensional versions of NTRU cryptosystem more secure?

The basis for this question is a 1-dimensional NTRU cryptosystem. After some literature inspection I have found out it can be also generalised into higher algebras: quaternions (QTRU) and octonions (...
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Does ECC give the most secure assymetric cipher for a given public key size?

Cracking an ideal block cipher is basically a brute force key enumeration. The complexity of the attack is exponential, growing as $2^b$. Cracking ECC is also exponential, but the cost grows as $2^{\...
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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 ...
Hubris4Monkeys's user avatar
3 votes
1 answer
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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 ...
khaled's user avatar
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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 ...
Nicha59's user avatar
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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 ...
Kagura Hitoha's user avatar
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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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1 answer
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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 ...
Stefan's user avatar
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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? ...
user569825's user avatar
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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
1 vote
1 answer
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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 ...
Allgaeuer's user avatar
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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 ...
Aravind A's user avatar
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2 votes
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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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