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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Public Key VS Wallet Address - What is the difference? [migrated]

I am seeing a lot of contradictory information on why we now use Wallet Addresses rather than Public Keys. Some say that due to additional level of hashing (double hashing), Wallet addresses are ...
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Does larger key size mean larger data size in asymmetric encryption?

I'm new to cryptography. I know the larger the key size (like 128-bit vs 1024-bit) the harder the ciphertext is to crack, generally. But assuming everything else being equal, does a larger key size ...
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Asymmetric Encryption - How is the Public Key Being Shared?

I've been reading up on the relationship between private keys and public keys (as well as hashing), and I watched a few videos, but I am still a bit confused. I don't have a programming background, ...
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Generating Public Key For ECDH with Botan (C++) [on hold]

I am trying to implement ECDH with Botan by using C++. First, I generated two private keys. Yet, I could not handle to make it for public keys. Botan::AutoSeeded_RNG rng; // ec domain and Botan::...
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Sign file (Client-Server) PKI-CA

I have a use case, the IoT system sending a signed file to the Datacenter and I have an internal CA to read the corresponding public key to verify the signature on the signed file. I am not sure how ...
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Single Ciphertext which can decrypt with multiple keys

Say we have a public key system where we have 2 users, Alice and Bob each has a public and private key. We also have a publicly available server which stores a message. I want to encrypt this ...
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Why is the NIST recommendation for the private key exponent so much smaller than the modulus?

NIST recommends a 256-bit private key exponent for DLP with a 3072-bit modulus. This question answered how the modulus was chosen/calculated, however, why isn't the private key size closer to the ...
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I need to send 16 bytes using ECC keys on a resource-constrained device

I have a system where a resource-constrained device has to send 16 bytes. It has its ECC key pair, and a peer's Public ECC Key. We're using the p256 curve. The device also has an AES-128 hardware ...
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How to let CA signed x509 key work in OpenPGP mailing system?

So let's say we have a OpenPGP mailing system which all mails are signed and encrypted with OpenPGP keys. And now you bought a CA signed x509 certificate and you want to imement into the mailing ...
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774 views

Can a public key be same as private key?

As I understand, we choose the public and private keys to be mutual inverses. However, it is possible that, in a group, there can be numbers which are their own inverses. E.g. Consider p = 7, q = 3. n ...
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How can I prove that the plaintext of an elgamal ciphertext is the discrete log of an element?

Is there any (efficient) method to prove that the plaintext of an ElGamal ciphertext is the discrete log of an element? In the scenario I concerned, I have an El Gamal key pair $(pk, sk) = (g^y, y)$....
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Are there any asymmetric key encryption/decryption algorithms?

When it comes to encrypting some data (where data being something of a large size), symmetric key cryptosystem is predominant. Symmetric key algorithms like AES, DES, Blowfish, IDEA etc. are ...
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Is it safe to reuse a ECDSA nonce for two signatures if the public keys are different?

We denote the s value of an ECDSA signature $(r, s)$ on a message $m$ as: $s=\frac{H(m)+xr}{k}$ Assume two ECDSA signatures sharing the same nonce $(r, s_1) , (r, s_2)$ on two messages $m_1, m_2$, ...
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Off-Chain Channel With Multi Participants That Have Different View/Write Access

I'm looking to expand my blockchain ability to have off-chain channels between different participants (let's say more than 2 participants). The requirements: Only the participants of the channel ...
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Post-quantum alternative to ElGamal? (public key verifiability)

Are there any alternatives to ElGamal that would be resistant/annoying to quantum machines? I would like to preserve public key derivability/verifiability -- ability to ensure existence of ...
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How are public keys securely and reliably obtained across the internet?

I've just decided to start learning all about PKIs, and I have come across what seems like a paradox. When fetching a public key from either a server or a CA, how can we be sure that the public key ...
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In theory, are there algorithms where everybody can read a message but only one person can write it?

I know that there are a lot of asymmetric algorithms out there that use the public key to encrypt and the private key to decrypt. I was thinking about having exactly the opposite. I do also know that ...
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Does anyone know an easily creatable asymmetric cryptosystem for usage in VDF?

I've read multiple papers about VDFs (1, 2, etc.). I look for a lighter alternative to El-Gamal regarding cryptosystem creation. It can be anything exotic too, but it would be nice to have at least ...
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How hard is to figure out the ENCRYPTION key given message and clear text?

How feasible is to brute force the ENCRYPTION key if you have the clear-text message the encrypted-version of the same message you know that Rijandel is the encryption algorithm you know that the ...
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What's the difference between symmetric and asymmetic multilinear map?

In pairing-based cryptography, we have 3 types, namely Type-I, where $\mathbb{G}_1 = \mathbb{G}_2$, and in Type-II and Type-III we have that $\mathbb{G}_1 \neq \mathbb{G}_2$, however in Type-II we ...
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In which public key encryption algorithms are the private and public key not reversible?

The RSA public key encryption system has the characteristic that the public key and the private key can be reversed. That is, information encrypted with the public key can be decrypted with the ...
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Alternate to distributing master key to every user in circle of trust

I am designing an end-to-end encrypted file storage system where only the user should be able to access their own data. The best I could come up with is a system designed around a master key that is ...
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How to get a random point of a specific EC group with cofactor Not-Equal 1?

We got a EC group generated with point G, and the cofactor of E(G) is with the similar size of the Order. Now we need a random point of E(G) and not revealing the "logarithm" of the random point, so ...
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How are old encrypted messages recovered for the sender?

Take ProtonMail as an example. It encrypts all emails with some kind of asymmetric keys. But obviously, they can't store my private so the key must be obtained when I log in. This means, they must be ...
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Can the original data be extracted from an RSA private key signed message

I'm working on a system that the main objective is to verify the message was written by the right person, but it would also be desirable if the message can't be understood by anyone sniffing it. It ...
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Should I PGP encrypt using a publickey intended only for Certify?

I'm working with a publickey that does not include EncryptStorage or EncryptCommunication flags (see RFC4880 for flag reference). My question is, is it safe/appropriate to encrypt using this key? <...
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What does it imply if in RSA pow(m, e, n) is same as the m

So, Let's assume we have n which is made up of 2 strong primes which cannot be factored & e which is textbook value of e ...
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Digital signature that is only verifiable by one specific person

I would like to digitally sign a message in such a way that the signature can only be verified by one specific person. Simply encrypting the signature will not work, because that person could then ...
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Probabilistic verification of signature schemes like RSA?

I was wondering if there were any verification algorithm in the literature that enables a "probabilistic" verification of well-known signature schemes? For RSA signature verification for example, is ...
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What is the difference between these pairings classifications?

I know the basic definitions of bilinear groups. For example, there is a bilinear pairing that uses elliptic curves and has the following properties: For $G_1$, and $G_2$ are cyclic groups of prime ...
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Help to understand the KDM in SP800-56A, and the usage of “FixedInfo”

Can somebody help me to understand the LOGIC behind Key-Derivation Methods (SP800 56A CH5.8)? This is my common understanding and please correct me if any wrong.. Alice and Bob can general individual ...
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Question regarding of the ECC test vector format

I am trying to find some ECC test vector for using. I just find some post (like this) and github resource (like this ) They are good reference to my C test code but I'd like to get some more advice... ...
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question about RSA [duplicate]

I am very new in cryptography field, what I want to ask but I cannot find an answer is this: In public key cryptography, such as in RSA, does it matter if the adversary knows/can detect the public key?...
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Asymmetric keys (e.g. RSA) must be so much longer than symmetric keys (e.g. AES). Why? [duplicate]

I have been reading that RSA has to do with math (prime numbers), while symmetric key encryption deals with blocks of data and modifying the blocks with replacements and remappings, but I still don't ...
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Key Value Based Key Derivation

For a system that is using public key cryptography to authenticate users and their actions I'm trying to solve (ease) UI/UX problem so that users will be able to use login/passwords they're accustomed ...
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Difference between RSA & ECC [duplicate]

My question is regarding Asymmetric-key encryption, in which situation is better to use RSA? What are the advantages of RSA comparison with ECC but from a security point of view? Thank you
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Looking for commutative asymmetric cipher for data matching

I need some crypto operation for matching data privately between two peers (let say Alice and Bob). Alice should be able to encrypt her data with Alice and Bob public keys and pass the cipher text to ...
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NTRUencrypt in NIST competition

Why did the NTRUencrypt team not maintain the NTRU1024 release in the NIST second-round competition? Is this because of the speed performance or security performance or other things?
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Security of an Elliptic Curve Public Key with a “Small” x-coordinate

Consider an elliptic curve over a finite field $F_p$ with $p$ prime and order $n$. Let $Q$ be a generator for the field. Given a public key point $P = aQ$, suppose we have an algorithm that finds an ...
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Is there a public-key system that can chain?

Does there exist any asymmetric cryptosystem that has the following properties: If I know somebody's public key PBK_1 and my own key pair (PVK_2,PBK_2), I can construct a new public key PBK_3 such ...
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RSA How to find the exponent ($e$) of the Public key with the values $p$ $q$ and an example are given

I'm wondering if it's possible to find the public exponent ($e$) with an example and the (rather small) values of $p$ and $q$ given. Currently the only option I found is bruteforcing this value, but ...
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EC Key Compression

Using the secp256k1 curve, will the below yield the same result? Generate private key -> compress private key -> generate public key Generate private key -> generate public key -> compress public key ...
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1answer
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Will publishing two or more public keys of the same RSA private key cause a security risk?

I want to make an end-to-end messaging platform where everyone is identified with a unique random private key. Everyone uses other peers' public keys to identify and send encrypted messages and verify ...
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1answer
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DH prime size required to force an attack of $2^N$ steps

Why the size of a DH prime $p$ should be about 6800 bits long to force an attacker to perform $2^{128}$ steps to attack the system? How is this relationship 6800-128 established?
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PKI Multiple Samples start to expose Private Keys?

My understanding is that using a PKI, public/private key pair is generally secure to send message to people. That is, encrypt a message using the recipient's public key so they use their private key ...
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What is the actual result of a Logjam's DH attack?

Does a Logjam attack calculate a group of probable Diffie-Hellman private keys for a user and then try them one at a time to see if it can decrypt the message - or does it directly calculate the one ...
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ECC with 512bit compatible curves

I understand that given solutions for solving a discrete logarithm problem are on the order of 𝑂(2𝑛/2), ergo, 256bit private keys based on 25519 or secp256k1 have an effective bit strength of ...
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1answer
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How to calculate e if we know n,p,q,m,c? [duplicate]

If we know n, p, q, and we have an encrypt oracle, which means we can input any plaintext and we'll get its ciphertext, and here p is smooth, which means the factors of p-1 are very small, is that ...
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1answer
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Why is D_K only required to be infeasible to derive from E_K for almost every key K?

In DH76 'New Directions in Cryptography', it states that 3) for almost every $K \in \{K\}$, each easily computed algorithm equivalent to $D_K$ is computationally infeasible to derive from $E_K$ ($...
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Flexibility in $RSA$ and $DLOG$ standards?

Today's security is based on $RSA$ and $DLOG$ primarily. If both go down then it is hard to imagine a scenario where internet can be salvaged quickly. Assume $RSA$ with $n$ bit prime factors and $...