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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 ...

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How to encrypt sensitive files in a business application? Is it needed?

I'm currently working on a business Java application, and we store sensitive files related to our users. What is the appropriate approach to store them securely? Is it viable to encrypt/decrypt all ...
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68 views

Newbie question: one-way functions in cryptography

I'm reading this article on the basics of cryptography and it says that the main principle is about taking such an algorithm that knowing the end result and the algorithm, an eavesdropper wouldn't be ...
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Asymmetrical encryption with multiple sufficient key-pairs [duplicate]

I have the following requirement: There are N public/private RSA key pairs. The encrypted data must be decryptable by any of the private keys alone, but not by any other key. For encryption, the ...
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50 views

Is it necessary to encrypt messages client side if using HTTPS? [migrated]

I am creating a messaging service for an app I'm developing and right now the data flow is as follows: Send: message sent to server => message encrypted based on user's public key and signed using ...
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1answer
47 views

Applicability of physical unclonable functions for public-key cryptography

Can physical unclonable functions (PUFs) be used to protect secrets against physical tampering in the context of public-key cryptography? Some solutions (i.e. ChipDNA or QuiddiKey) apparently use ...
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77 views

Cryptographic scheme where a single message cannot be decrypted but if combined with other it can be

i'm wondering if this type of cryptographic scheme does exists. I know about homomorphic encryption but if one has the private key, he can decrypt every single message. I would like to know if there ...
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72 views

Does this scheme break under a DHP adversary?

Consider the following cryptography scheme: We are given a prime $p$. Alice wants to send the plaintext $m \pmod p$ to Bob. Alice chooses $a$ s.t. $\text{gcd}(a,p-1)=1$, and sends Bob, $u = m^a \...
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38 views

Private Key Sharding - How is it Secure in a Distributed Network?

In a Distributed Network in order for a private key not to be compromised sharding will have to take place off the network, correct? If so: Why is it when a Distributed Network shards private keys ...
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3answers
108 views

Could ANY cipher serve as the foundation for a public key cryptosystem?

My reasoning goes like this: In principle, any trapdoor function can serve as the foundation for an asymmetric encryption scheme. All ciphers are trapdoor functions, since it's easier to encrypt ...
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40 views

Can one design an asymmetric encryption scheme based on any secret sharing scheme? Are they that closely related?

I've seen both asymmetric encryption and secret sharing schemes based on graph 3-coloring, and I'm curious if this is a coincidence due to some peculiar property of graph 3-coloring alone.
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How to use public/private keys in elliptic curve cryptography to encrypt/decrypt information

I'm reading a bit about elliptical curve cryptography. The basic idea is to define a dot-operator on the points of an elliptic curve. Given a starting point $P$, and applying this dot-operation $n$ ...
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5answers
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Encrypt a file in a way that decryption requires every recipient's cooperation

The best related concept I can think of is the two-man rule. https://en.wikipedia.org/wiki/Two-man_rule. To put it simply, n people are required to give their authorization before a system / secret ...
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71 views

What is it known about the hardness of the factorization search problem in non-commutative crypto?

The factorization search is an interesting problem in non-commutative crypto that can be defined as: Given an element $c$ of a group $G$, two subgroups $A,B \leqslant G$. Find two elements $a\in A$ ...
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34 views

Algebraic Span on non-commutative groups

I'm interested on non-commutative cryptography. Some time ago here Adi Ben-Zvi, Arkadius Kalka, and Boaz Tsaban demonstrated how to find a solution to some of the well known PKE protocols based on ...
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1answer
77 views

Random Masking of Padded RSA Ciphertext through homomorphism

I had asked a question related to this before: Oblivious Decryption: Decrypting with a private key, without knowing the message @rikhavshah has an answer, which I would like to discuss the security ...
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1answer
73 views

Restoring a point on an elliptic curve

I received a representation of a point on an elliptic curve $GF(2^m)$ (with curve coefficient A, B) in specific format and some description how to decode it but not all is clear to me. I would be ...
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46 views

How to calculate Trace function for a point on an elliptic curve

I encountered trouble with calculating Tr (trace function) for points on an elliptic curve in polynomial basis ( $GF(2^m), m = 431$). Maybe there are any assumptions that can simplify and allow ...
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Finite Automata and Application to Cryptography

The automated inverse theory in cryptography, points to autonomous finite automata, which is relative to the canonical form for one-key cryptosystems based on finite automata, the public key ...
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162 views

If the Riemann hypothesis solved

"Sir Michael Atiyah claims to have demonstrated a simple solution to the Riemann hypothesis". If solved, what results we will have in Cryptography?
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2answers
79 views

Oblivious Decryption: Decrypting with a private key, without knowing the message

I’m trying to devise a protocol, complimentary to a private-set-intersection, involving three parties, namely Alice, Bob and Charlie. Alice has a public and a private key. And receives website logs ...
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1answer
62 views

Could one make an asymmetric encryption scheme based on Sudoku?

I was reading about a Polly Cracker encryption scheme based on the graph 3-coloring problem. Aren't Latin squares just a form of the same problem? If so, does this mean Sudoku can be used for public/...
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2answers
71 views

Can a digital signature scheme also be an encryption scheme?

Using Schnorr signatures, one could devise a system where a single public key can represent multiple signers. Do signature schemes like that represent crypto systems usable for encryption? In that ...
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68 views

Is it Ok to reverse the usage of public key and private key

Well things like this, my coworker suggest exchange the private key between server and client and using public key to decrypt message privately, his reason is, this is just the same as normal usage, ...
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1answer
54 views

RSA: Private key given public key, plain text, and cipher text with no padding?

Are there attacks which will return the RSA private key when the attacker knows the public key, plain text, and cipher text when no padding is used in the RSA algorithm? If yes, what are the known ...
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2answers
37 views

Public key encryption and decryption with private key [closed]

I am learning cryptography and here is what I understood so far: Story. I decide to talk with my friend over unencrypted channel. We exchange public keys with each other so that we can encrypt ...
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26 views

Adding new participants to a multiparty signature scheme

I'm looking for a signature scheme that allows a group of N parties, without the help of a trusted dealer, to: Jointly create a group public key $P$ Produce a valid signatures for an arbitrary ...
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1answer
41 views

How to generate tokens from a secret key?

The problem is simple: I want to be able to spit out 256-bit "tokens" that only I could've produced because I know my secret key $s$, and given any number of these tokens, no one can figure what $s$ ...
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2answers
32 views

Minimum number of public and private keys depending on signature?

I'm trying to make sure I understand and intuit things properly here, so I'm going to be somewhat lengthy? With this, as I did a cursory search here and couldn't find exactly the case examples I'm ...
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1answer
44 views

Certificate public key keyexchange, Which key exchange is used in browsers?

I have a question regarding the keyexchange happening in web browsers. If you check the certificate here on crypto.stackexchange you can go under details and see that the public key is type RSA (2048 ...
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1answer
50 views

is the functional signature result relies on f(x) or on x where x is a message and f is a function?

I am new on cryptography and I have a question about the functional signature scheme. The notion was introduced in this paper. In a functional signature scheme, there is a standard signature and ...
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2answers
88 views

How secure is a system that retrieves encrypted private keys from a public database?

The system in question is one with multiple users. Each user has a password associated with their account, and each user owns several public-private keypairs. A user's private keys are encrypted using ...
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Risks of using Asymmetric criptography for large file [duplicate]

I'm forced* to use asymetric cryptogrphy to encrypt large (say 5MB) files. Besides performance and the fact that I will get 128 bit of security (using RSA 4096) on the encrypted file, is there any ...
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50 views

Oblivious Encryption: Oblivious Transfer Based Encryption

I’m aware of a couple of OT protocols, most of which use Public Key Cryptography, Key Establishment (or similar constructs) as the base. I don’t really have specific knowledge on other OT protocols, ...
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Encrypting with Asymmetric keys

I'm designing a system where the client asked for documents to be encrypted with "asymmetric cryptography". I've explained them that the best practice is to encrypt the data with a symmetric ...
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2answers
623 views

Can public key cryptography survive quantum computers? [duplicate]

Quantum computation is based on the superposition principle of quantum physics. Bits in a normal computer are either 0 or 1. Quantum physics allows bits to be in a superposition of 0 and 1, in the ...
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1answer
84 views

Using secp256k1 keys for encryption

We are making a system where users can share files with other people but nobody should be able to figure out that all these different files belongs to same user on blockchain. these are the steps we ...
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GPG Sub Key Renewal Questions

Last year, I followed this guide to create two GnuPG Smart Cards; one card with the Primary Key and the other card with the Sub-keys. I noticed that the sub keys were close to expiring so I renewed ...
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56 views

Broadcasting a message with multiple sub-messages encrypted for different recipients

I'm looking for an encryption scheme that can be used in a P2P system were broadcasting of messages is used to propagate these to all participants. A participant would create a single/large message, ...
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1answer
62 views

Implementing a zero-knowledge proof [duplicate]

I'm trying to get my head around zero-knowledge proofs and my definition of a zero-knowledge proof is as follows. A zero-knowledge proof is a method by which one party can prove to another party ...
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61 views

Issues with Elliptic Curve Point Addition

I'm trying to implement elliptic curve point addition in hardware. I've managed to create a working module using Affine coordinates however I've been reading about how points can be added by using ...
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2answers
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RSA public key of dead cryptographers

Two cryptographic schemes—RSA accumulators, and RSA-based Verifiable Delay Functions (VDFs) such as this one—require an RSA modulus to operate. These RSA constructions are secure if the trapdoor, ...
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1answer
72 views

What standards of ECC point compression exist?

The method that I used before to decode EC point from public key led me in a dead end. So I just want to know what yet I could try. I've got a public key that I don't know how to decode and I am ...
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44 views

General Private/Public key generation

I wanted to get an idea on how the whole cold-storage private/public key generation works for different cryptocurrencies. So I was playing around with BIP32 deriviation path on: https://iancoleman.io/...
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1answer
71 views

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 rhymes with vanilla asymmetrical crypto, but in every schema I've seen,...
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How is a ciphertext encrypted using random numbers decrypted using a symmetric key algorithm

We use true random number generators as a source of keys for encryption. What I can not wrap my head around is: How is this cipher text decrypted in case of symmetric key algorithm as we need the same ...
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1answer
45 views

Bitwise operation on secret values revealing the result only to the participants

Given the following situation, what sort of cryptographic construction am I looking for? Alice has a bitfield (vector, polynomial representation, etc.) Bob has a different bitfield of the same length ...
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61 views

Which one counted as key freshness must be freshness in session or each message send

Which one means key freshness 1 or 2 on Key Exchange 1: Changing private key to recomputes a new common key in whole session 2: Changing private key to recomputes a new common key whenever you send ...
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Public-private algorithm where it is not possible to recover public key from private key?

Is there an asymmetric algorithm where it is not possible to extract a public key from private key? So far any algorithms I tried (dsa, rsa, ecdsa, ed25519) successfully recover their public keys from ...
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How do i generate the shared key from this question?

Say I have Alice and Bob: Alice has $XA$, $YA = g^{XA} \bmod P$, $RA$ (random number) Bob has $XB$, $YB = g^{XB} \bmod P$, $RB$ (random number) Assume they have exchanged their certificates and ...