Cryptography

Questions tagged [public-key]

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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 private.

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Does CPA model the challenge plaintext are the same

For a CPA-secure encryption scheme, suppose that there is an adversary who can find that the two ciphertexts are encrypted from the same plaintext. Is this encryption scheme still CPA secure? Or, CPA ...
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Convert Ed25519 keys to usable format for Tor

I'm making an onion (v3) address generator in Python. Here is the part that generates the keypair: ...
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22 views

Private Key from Extended Private Key and Public Address [closed]

Is it possible to generate a private key from a public address and an extended private key? For context: I am using C# and NBitcoin. The public address is generated from the outside via an extended ...
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76 views

How to find integer point of a ec curve in a given range?

I was looking inside the basics of ecc and found the examples from Internet either uses continuous domain curve or use a very small prime number p like 17 in a ...
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Can Pollard Rho be used break cryptographic hash functions such as RIPEMD-160? [closed]

Can a Pollard Rho algorithm be used break cryptographic hash functions such as RIPEMD-160, so that the output would be a public key? If so, what are the estimated number of calculations based on the ...
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What is a good and bulletproof private key for ECC curves?

I am quite new to cryptography low-level mathematic details, though had worked in the crypto area for 2.5 years before. So if I am wrong about any of below part, please correct me without a facepalm ...
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User key management scheme: BYOK vs. client only keys vs. a mix of both

We are designing a web app where users can share documents with each other. The ultimate goal is to achieve zero trust needed by the users, i.e. client-side encryption makes sure that the servers (or ...
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How can I calculate the complexity of any encryption algorithm [closed]

I want to know if there are abasic steps to calculate the time complexity of any public-key encryption algorithm? Can anyone help me? or are there any papers or pdf that help me to calculate?
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Use Diffie Hellman to share a secret

I was trying to use Diffie Hellman to first agree on a key and then use that key to symmetrically share a secret. The python3 code using cryptography library look like ...
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29 views

Can I use a certificate authority with Elgamal encryption?

Can I use a certificate authority with Elgamal encryption? Is this type of keys in CA?
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Congruence in the Schnorr identification scheme

I have been looking at the Cryptography: Theory and Practice book by Stinson and Paterson and when I came to the Schnorr identification scheme, I read the sentence that goes something like this: ...
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Authentication between two servers using PKA

I've run into an small issue regarding authentication between 2 services (One way communication) using public and private key authentication (Elliptic Curve, secp256k1). The services will communicate ...
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Asymmetric cryptosystems based on curves besides elliptic curves

Elliptic curve cryptography (ECC) has been gaining a lot of popularity recently because of its security. I tend to find the process of encoding plaintext using ECC particularly interesting so I was ...
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Asymmetric Encryption Using Existing Secret Key

I'm using Python to build a system in which users (accounts on a blockchain: defined by a public key and a secret key) need to communicate with each other securely and I think asymmetric encryption is ...
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MuSig: could the rogue key attack be mitigated by using commitments instead of key transformations?

Background MuSig is an extension of/derivation from Schnorr signatures using cyclic groups on elliptic curves. In the original paper, the authors point out that naive multi-Schnorr is vulnerable to a ...
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Question on double-asymmetric encryption and split knowledge

Moin moin, Let‘s assume there are two keypairs (d1,e1) and (d2,e2), where d1 and ...
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(Non)security of algebraically derived EC keys

I recently had a situation where I needed to derive a secondary Curve25519 private key from an existing one programmatically. The obvious solution was to use a KDF, but I wondered at the time about ...
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Can we pick which key is private or public in asymmetric encryption? Do the keys actually encrypt and decrypt a cipher text?

Could you help me better understand how the key-pair works in Asymmetric encryption? I'm studying cryptography at the surface level first. While reading multiple texts and talking with colleagues I'm ...
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Can an arbitrary physical image be a key?

Assume an arbitrary secret physical image¹, such as a privately made chemical Polaroid™ similar to this Is there a feasible and secure way that this physical image could be used as cryptographic key, ...
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Saving highly sensitive data in US cloud - what encryption would you use?

We have a cloud-based application running on AWS servers and are looking for a way to store highly sensitive user data there without giving AWS the possibility of exposing our data to the US ...
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74 views

Proof that someone has access to a private key whose public key is part of a known group

I'm a crypto newbie and hoping to get pointed in the right direction. I've seen some related questions like this but none that satisfy my requirements. Let's say Jane's Forum is a large community, and ...
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Asymmetric encryption scheme with the shortest output for encrypting 1 byte of information

Imagine that one needs to periodically encrypt very short messages (i.e., a boolean Yes/No, a single byte, or 3-4 bytes in the worst case). We assume that there is no session, and we just need to ...
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How many keys are used in symmetric, asymmetric, and hybrid encryption?

There are 8 people in total working on a project. Each one of them will send information to the rest of the team individually 2 times a day. They use 6 days in total for this project. Cryptosystem 1: ...
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Why are NIST curves still used?

I'm relatively new to the world of crypto (But as far as the math goes, I am familiar with the inner workings. I used to rarely use it for privacy, but now I use it for many things). Anyway, I was ...
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Related Key Attack on Schnorr Signature - Why does the challenge include $\psi = g^x$, not $y$?

The original Schnorr signature scheme suffers from a Related Key Attack (RKA) as described by Morita et al. The authors of this paper then suggest a modification to the signature algorithm to prevent ...
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32 views

How to do the WOTS checksum

As far as I understand, the Winternitz one-time signature is made by: Making an array of private keys. Making an array of public keys by hashing each private key X times, X being the number of ...
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Why is an ephemeral key required to prove possession of a static private key in Key-Establishment Schemes

In the NIST 800-56A rev3 "Recommendation for Pair-Wise Key-Establishment Schemes Using Discrete Logarithm Cryptography" in section 5.6.2.2.3.2 "Recipient Obtains Assurance [of the ...
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What information is needed to be stored for RSA private key for decryption

I am using rsa module in Python. I use the following line to generate public and private key: ...
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87 views

Proof that a message is signed by a member of a group

I'm a newbie at cryptography. Here is my question: Alice makes a list of people: Bob, Carol and Dan; Alice gives a unique secret key to every member on the list, so they can uniquely sign messages; ...
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Generating public/private key pair without a trusted dealer

I want to make an Ethereum wallet where I can prove no one has the private keys in one place. Basically, I was wondering whether the ECDSA signatures could be generated by multiparty computation like ...
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How to determine whether a point is greater than n/2?

How can we determine if a private key associated with a point, on an EC, is less than or greater than 1/2 $n$, where $n$ is the order?
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677 views

How to determine if a point is just a point or a valid public key?

In ECC, specifically over finite fields, in my mind there must be other points that exist that still yield $y^2 \bmod p=x^3 + ax + b \bmod p$ to be true but are never used because the Generator Point (...
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What's the use of storing R^2 with a public key?

I think I have successfully reverse engineered a Samsung RSA public key here. However, the public key mainly seems to consist of the modulus, but it also contains a 32 bit integer ...
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177 views

Decrypt RSA with known public key and modulus and the range of dp

How to decrypt RSA while given $e$,$n$ and the range of $dp$ ? ...
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249 views

How many Bits/Bytes is a public key, given its encoding

I am struggling to understand what the "bit/byte" size of a public key is, how you can work it out, and even what it means. An example of a RSA public key is: AAAAB3NzaC1yc2EAAAABJQAAAQB/...
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366 views

Counterfeit EU Green Passes

In the EU, a person will soon be able to perform certain activities (going to concerts, to sports events, etc.) only if they can present a valid Green Pass that certifies that the bearer has been ...
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What is the security implication of non-full-rank systematic matrix in McEliece cryptosystem?

The Classic McEliece cryptosystem has the following key generation procedure: Choose a field $\mathbb{F}_{2^m}$, an irreducible polynomial $g(x)$ of degree $t$, and $n$ field elements $\alpha_1, \...
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What uses are there (if any) for asymmetric message encryption?

What uses are there (if any) for asymmetric encryption of a message, instead of hybrid encryption? Specifically, I'm not considering asymmetric encryption of a symmetric key (eg old TLS RSA key ...
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How to hack pass-protected private RSA key

I know nothing about cryptography. I must present a completed ASP project to my university that proves I have learned clingo. I have heard that the task of recovering the plaintext private RSA key ...
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1answer
75 views

Can CPA secure scheme be converted to CCA secure?

I would like to know if there are some methods or techniques that can convert a public key encryption scheme from CPA secure to CCA secure?
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Coding gain and minimum determinant in cryptography

In coding theory, the notions of coding gain and minimum determinant of a code have been defined as follows: let $\mathcal{X}$ be a (full diversity) code and $X,X^\prime\in\mathcal{X}$. Then the $\...
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Zero knowledge RSA public key

Suppose Bob has $k>1$ RSA public keys $(e_i, n_i)$ without any knowledge of their corresponding private keys. Alice also has all the public keys, but also has a private key for only one of them, ...
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The security level of secret share compared to homomorphic encryption

I want to compare additive secret share to Paillier encryption. However, I haven't found out how to set the parameters in such a way that the security level is consistent. Additive secret share (...
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1answer
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Is the relationship between private and public keys an example of bijection between two sets?

Just want to make sure that my understanding is correct whether there is only one public key for any private key, and vice versa. I know that there are many algorithms, and this may not be a property ...
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1answer
51 views

How much much data can be verified by an electronic signature?

I’m trying to get a good understanding of how data encryption and signing work. I imagine these vary a bit depending on the software being used. In particular, I am wondering about this: how much data ...
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Combining WireGuard keys

I suspect the answer is "no", but still: In WireGuard [1], there's a concept of private and public keys for peers; public key derives from a private one and connection between two parties ...
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Can one prove that a particular public key is part of an aggregated (MuSig) public key?

The MuSig paper (2018) describes a Schnorr signature key aggregation scheme which lets a set of individual public keys to be merged into a single, "aggregated" public key. In the protocol ...
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Public key size for different elliptic curves

Let's say I want a certain level of security (eg 128 bits) when using ECIES but I also want to minimise communication, does the elliptic curve used matter on the size of the public key? If it does ...
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Algorithm to ensure m people signed off on a task out of a group of N

I have a task that needs M people to approve out of a group of N. I can obviously implement it in software using a basic ECC signature mechanism. The code on the "server" can send request ...
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Is there an asymmetric encryption protocol which provides arbitrarily many seemingly unrelated public keys for a single private key?

I am looking for an encryption protocol with the following properties. Alice has a private key $x$. Using this private key, she chooses public key $p$ corresponding to this private key. She let's Bob ...

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