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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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Rolling Code via Encrypted Index vs Pre-Generated Keys

I am planning on designing a system that needs a password to be operated, using a rolling key. Now I am facing two options, as far as I am concerned: Having an index saved, which will be incremented ...
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The goal, the method, and the interface of the signcrypt primitive.

Some time ago, I proposed making the site more educational by teaching correct cryptographic programming. The proposal had had somewhat good reception, but was met with cold ice as there had been ...
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Size of group for Elliptic curves vs RSA for equal security

For my research, I would like to compare the efficiency of a scheme when instantiated with Elliptic curves and RSA. So, I would like to know a "latest" comparison (as of 2018) on what group sizes of ...
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How much information of the length of a plaintext can an adversary get from its ciphertext?

Let $\Pi$ be a public-key encryption scheme. For every palintext $x \in \{0,1\}^{*}$, is there a PPT adversary $A$ such that $$\Pr \left[ 1^{|x|} \leftarrow A\left( pk, \mathrm{Enc}_{pk} (x) \right) \...
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Why public host key still need be sent in SSH_MSG_KEX_DH_GEX_REPLY?

RFC 4251(https://tools.ietf.org/html/rfc4251) states, [page 4] The protocol provides the option that the server name - host key association is not checked when connecting to the host for the ...
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Parameters and key dimension for DH and RSA

I studied RSA and Diffie-Hellman key exchange from a quite old book (Discrete Mathematics by Berardi, Beutelspacher) and so I wonder if the recommended dimensions for the prime p and the secret ...
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Is a good idea to generate a public key from a secret key using a functional encryption scheme?

FE - functional encryption PK - public key I want to design a PK cryptosystem that has a unique PK for each encryptor. Namely, the encryptor submits a unique value (or an attribute) to the private ...
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Securely register a client in server using AES an RSA

I've designed the following protocol to send the client's public key to the server. Initially, the client knows server's public key, but the server does not know the client's public key. client draws ...
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Is it possible to have E=D and Ke <> Kd?

Let us consider $E$ an encryption algorithm that encrypts a message $m$ into a ciphertext $c$ using a key $K_e$. i.e $c = E(K_e, m)$. Similarly, decryption is achieved by $m = D(K_d, c)$. Is there ...
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Defining correct secured channel from endpoint to server

I'm new to cryptography and have a question regarding encryption usage. The scenario is as follows: I have an endpoint hardware device (CPU - ARM A7 1.2 ghz) which runs Ubuntu 14.04. This hardware ...
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Public key of a split key without calculating private key

I am searching for a secret splitting scheme where the private key doesn't exist, since each party chooses their own secrets. The other parties should however still be able to calculate the public key....
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Property of Multiplicative group of integers mod n

While practising on paper I've realized of a property of multiplicative group of integers mod $n$. First, let's define $G$ being $p$ a prime and $g$ a primitive root mod n or a generator of a ...
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What crypto scheme should I use on embedded m2m system with assymetric uplink/downlink bandwidth?

I am working on implementing info security into custom m2m radiolink communication system, which has some restrictions: MCU based endpoint can transmit to gateway with packets max 16 bytes long, and ...
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What work goes into creating new asymmetric cryptosystems?

It's seems to me that it is rather easy to create a symmetric encryption algorithm (though not necessarily a secure one). They're a dime a dozen. The number of asymmetric encryption algorithms ...
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Strategies for securing public key storage on software

I´m kind of new in this so I apologize in advance for any noob mistakes (feel free to point it out) We are developing a licensing mechanism on our software, and I would like some advice. The ...
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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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How is public key cryptography used for digital signature?

In public key cryptography, there are two different keys used for the encryption and decryption of data . I am wondering how it is used for digital signature
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Diffie-Hellman key exchange in four parties

I understand the concept of 2 and 3 parties Here is the code of 3 parties ...
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Authenticating Public Keys Recieved On Blockchain PKI

I am trying to understand how a PKI could be stored on a blockchain so as to eliminate the need for centralised CAs. How does every node on the network who receives a new block containing an ...
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Deterministic procedure for mapping an arbitrary value into a 𝑝,𝑞 pair for public 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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516 views

how to encrypt the chat message with multiple people public key together and restore the message?

I have a application with two users and one middle man, all of them holding the private and public key, To make the secured chat, two users and one middle man are all sending the public key and ...
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Simple hexadecimal to 2s complement question

From 2.5.1 in this paper, how is $p$ = FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFE FFFFFFFF 00000000 00000000 FFFFFFFF = $2^{384} − 2^{128} − 2^{96} + 2^{32} − 1$ ...
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How can I prove CPA secure by using a new scheme gen,enc,dec from GEN,ENC,DEC?

Given public key encryption scheme $(\mathit{gen}; \mathit{enc}; \mathit{dec})$, we now construct a new scheme $(\mathit{Gen}; \mathit{Enc}; \mathit{Dec})$ as follows: The key generation algorithm $\...
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Diffie-Hellman (Public Key exchange)

I have read a few tutorials in regards to this. My understanding is that Diffie-Hellman is a key exchange concept that is being use everywhere in our daily lives, which is also known as the public-...
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Can two different CA's/End Entities in different PKI's have the same asymmetric key pair?

Example: $X$ and $Y$ have the same asymmetric key pair. $X$ communicates with $A$ and gives it's PubKey to $A$. So, $A$ has the PubKey of $X$ which also happens to be the PubKey/PrivKey of $Y$. ...
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How to distinguish between private key and public which are visible in text editors?

I would like to know how to understand which one is private key and public key while seeing them in raw text format?