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.

Filter by
Sorted by
Tagged with
0
votes
1answer
28 views

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 / ...
0
votes
0answers
28 views

Backdoor Hash Streebog (?) [on hold]

There was a news that possibly has a backdoor hash Streebog. https://twitter.com/bascule/status/1094830326201835521 https://www.golem.de/news/kuznyechik-streebog-russische-...
1
vote
0answers
15 views

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 ...
4
votes
0answers
61 views

Is it possible to construct a hash-based public key encryption scheme?

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 ...
0
votes
1answer
60 views

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 : ...
2
votes
0answers
65 views

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 ...
0
votes
0answers
13 views

Differences between ssh-keygen private keys and libressl's? [migrated]

I generated a private key using libressl 3.0 using curve secp521r1. ...
1
vote
2answers
64 views

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 ...
-1
votes
1answer
62 views

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 $$ \phi=(P-1)(Q-1)=3016 $$ $$...
1
vote
1answer
49 views

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 ...
1
vote
1answer
102 views

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 ...
0
votes
2answers
83 views

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 ...
0
votes
0answers
20 views

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 <...
-1
votes
1answer
61 views

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 ...
1
vote
0answers
26 views

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 ...
2
votes
1answer
44 views

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/...
2
votes
0answers
81 views

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 ...
5
votes
2answers
887 views

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 ...
1
vote
0answers
81 views

How is the PRIVATE KEY actually created in the first place? [migrated]

How is the "Private Key" created in the first place? I understand that once you have your wallet, you will also gain access to your public key and private key... But in order to have a wallet ...
-1
votes
0answers
28 views

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 ...
4
votes
4answers
85 views

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 ...
1
vote
1answer
67 views

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, ...
1
vote
0answers
26 views

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 ...
6
votes
1answer
115 views

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 ...
3
votes
1answer
138 views

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 ...
1
vote
0answers
50 views

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 ...
0
votes
0answers
7 views

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 ...
3
votes
1answer
799 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 ...
1
vote
0answers
60 views

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 $(pk, sk) = (g^y, y)$....
1
vote
1answer
51 views

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 ...
13
votes
2answers
569 views

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 $m_1, m_2$, ...
0
votes
0answers
17 views

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 ...
2
votes
1answer
55 views

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 ...
1
vote
1answer
57 views

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 ...
0
votes
2answers
134 views

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 ...
2
votes
1answer
64 views

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 ...
0
votes
1answer
79 views

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 ...
3
votes
1answer
40 views

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 ...
3
votes
1answer
1k views

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 ...
0
votes
0answers
30 views

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 ...
0
votes
0answers
27 views

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 ...
1
vote
1answer
28 views

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 ...
2
votes
1answer
66 views

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 ...
2
votes
1answer
44 views

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? <...
0
votes
1answer
90 views

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 ...
18
votes
3answers
3k views

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 ...
0
votes
1answer
44 views

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 ...
0
votes
0answers
18 views

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 ...
0
votes
2answers
38 views

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 ...
0
votes
1answer
55 views

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... ...