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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Perfect secrecy public key scheme

Are there public key schemes that have perfect secrecy? The perfect secrecy notion is defined for symmetric key encryption. If P is a message and C the corresponding ciphertext then the cipher has ...
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How are blockchain keypair private keys hidden from miners, and how are they generated in the first place? [on hold]

I don't know how blockchain keypairs are programmatically generated, and equally important - how they are able to verify their keypair using a private key to a remote server - while keeping their ...
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Elliptic Curve 256 public key in readable (DER?) format in .NET Core [migrated]

I have .NET core application and EC 256 public key as point of a curve (x and y) in the following format ...
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What is Reverse Trapdoor Function?

In wikipedia on Digital_signature: but rather, the message to be signed is first hashed to produce a short digest, that is then padded to larger width comparable to N, then signed with the ...
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The security level of double encryption

Let PKE $\Pi' = (Gen', Enc', Dec')$ and it is secure in the sense of $S'$. Let PKE $\Pi'' = (Gen'', Enc'', Dec'')$ and it is secure in the sense of $S''$. $S'$ and $S''$ may be separation which ...
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How are precision and security related in a Gaussian Noise Sampler for R-LWE?

My understanding is that the sampling precision in Gaussian Noise sampler is related to security. But not sure about why is that? I read that when the samples are floating-point numbers and precision ...
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asymmetric encryption with rekeying in an untrusted environment

Alice can retrieve asymmetric encrypted messages (let's call one of them C1 and the Message itself M) for her from an untrusted environment (let's call it Eve). She owns her private key K1 and has ...
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Why isn't semiprime encryption reversible? [closed]

I understand that semiprime encryption works by having private keys (prime factors) and public keys (semiprime), but what I don't see is how you can encrypt with a semiprime but not decrypt with it. ...
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Is using different public keys for different peers safer than reusing the public key, beyond forward secrecy?

In X25519 (ECDH over Curve25519) Peer A and B exchange their Public Keys ...
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Deterministic procedure for mapping an arbitrary value into a 𝑝,𝑞 pair for pubic key cryptography

I want public key cryptosystem to used for re-encryption as describe in Can Paillier ,RSA or any other schemes be used for universal re-encryption like elGamal? Now i have little solution for ...
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Can Paillier ,RSA or any other schemes be used for universal re-encryption like elGamal?

ElGamal, RSA, and Paillier cryptosystem have homomorphic property, and can be used fro re-encryption purposes. I want to use the encryption to re-encrypt ciphertext(as in proxy re-encryption but ...
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Can Paillier Encryption has independent decryption key?

As Pailliear cryptosystem secret key $\lambda$, depends on primes $p$ and $q$. As $\lambda = \operatorname{lcm}(p-1,q-1)$. I want decryption key to independent from $p$ and $q$. It can be possible ...
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How Paillier cryptosystem can be used practically to encrypt and decrypt big messages “m”?

I want to use the Paillier cryptosystem for encryption and decryption purposes in my research work. But i haven't found a way to encrypt big input messages; As i want to encrypt the message i,e m : <...
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Is there any relationship between Paillier Cryptosystem's random r and other factors

I want to try run an example of Paillier cryptosystem(Algorithm), So i just started with some basic examples, but cannot obtain correct result/decryption. I just change random factor ...
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Multiple sender single receiver Encryption

I had this article given to me by my teacher, and I would like to enhance it. It's titled Modified El Gamal Algorithm for Multiple Senders and Single Receiver Encryption. I planned on having the ...
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What is the difference between “asymmetric key cryptosystem” “asymmetric cryptography” terminology?

What is the difference between "asymmetric cryptography" and "asymmetric key cryptosystem" terminology?
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How re-encryption can be done through RSA

Both RSA and Elgamal have homomorphic properties. So both can re-encrypt the ciphertext. Re-encryption with Elgamal works as seen here. How does re-encryption work using RSA? What modification / ...
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How do I calculate key rotation schedules?

tl;dr: How do I formulaically determine key rotation schedules for different kinds of keys and use cases? The organization I'm a part of for utilizes both symmetric and public/private key encryption ...
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Is it possible to construct a hash-based public key encryption scheme? [duplicate]

I know hashes can be used to construct symmetric encryption schemes (HMAC running in counter mode), signature schemes (SPHINCS), pseudorandom generators, etc. One thing that's missing is public key ...
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NaCl allows decryption with the same public key as for encryption

I followed the description here: Public-key authenticated encryption: crypto_box and created an example that encrypts a message with Bob's public key and signs it with Alice's secret key : ...
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Is it possible to verify attributes of encrypted content?

Let's say that Alice has this information about her, { "name": "Alice", "age": 25, "eyes": "brown" } which she encrypts with a key pair so that no one access ...
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Using public-key signature instead of having API key

I am designing an application that will need an API key. At first I believed that generating a long, random token would be secure enough (say 32 chars string that includes 0-9, a-z and A-Z), and then ...
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Can't understand the magic of relationship between private an public key functions

To encrypt a message $$ P = 53, Q=59, n=PQ=3127, e =3 $$ let message M, for example, $ 89 $$ cipher = 89^{e}mod\quad n. $$ cipher = 1394 this is the encrypted message $$ \phi=(P-1)(Q-1)=3016 $$ $$...
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Is there a zero knowledge proof to show an encrypted blob is the key for a given public key?

Let's say I have a private key x with a corresponding public key y. If I encrypt x as ...
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Could public-key crypto be performed long ago if the idea had been discovered?

Public-key cryptography was not invented until the 1970's. Apart from the idea not existing earlier (as talked about here), is there any reason it could not have been used earlier? For example, are ...
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Discrete logarithms on elliptic curves

In many examples of attacks on public key cryptography, examples of the form $a ^ x = b$ are used, but I can not understand the correlation between this and the multiplication of the generator point ...
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aspnet_regiis private key storage

I am using aspnet_regiis.exe to Encrypt a connectionStrings on an ASP.Net application. The application in productions runs on a <...
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P256 Key size and validation [duplicate]

Given a public key on the P-256 Curve is it correct to say that the public key is 64 bytes long ie. (x,y)? Secondly is the private key 32 bytes long? if so, how is the private key generated and why ...
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Asymetric encryption, multiple recipients, traitor must share private key

Is there an Asymetric encryption scheme, or public key encryption, where multiple recipients are able to access the data but in order for one of the recipients to leak the key to the data they would ...
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Where does signing/decrypting take place on a YubiKey 4/5 PIV private key?

I have a YubiKey 4 and want to use it to store a private key that should never enter a computer system's memory. After importing the key to the device I understand it never leaves it. Do the signing/...
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A proposal for randomization of Niederreiter cryptosystem

The Niederreiter cryptosystem is a public key cryptosystem using Goppa code. Unfortunately it it is insecure unless it is a binary code. So I thought I could insert random linear codes into randomly ...
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Raw curve25519 public key points

I'm trying to understand curve25519, and ECC public points. I'm playing with Minisign, to better understand the fundamentals of ECC. Minisign uses curve25519 and outputs public keys as base64 ...
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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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Sign file (Client-Server) PKI-CA [closed]

I have a use case, the IoT system sending a signed file to the data center and I have an internal CA to read the corresponding public key to verify the signature on the signed file. I am not sure ...
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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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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 ...