Cryptography Stack Exchange
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Questions tagged [elgamal-encryption]

ElGamal is a public key encryption scheme with security based on the discrete logarithm problem.

ElGamal is a public key encryption scheme. Its security relies the hardness of a problem (called decisional Diffie-Hellman) that is related to the discrete logarithm problem.

The encryption scheme is notable for being randomized (allowing CPA-security) and multiplicatively homomorphic.

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ElGamal with elliptic curves

I've searched some information on ECC, but so far I have only found Diffie-Hellman key-exchange implementations using ECC, but I don't want to exchange keys, I want to encrypt & decrypt data like in ElGamal. I know that ElGamal with elliptic curves…
CriticalError
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When to use RSA and when ElGamal asymmetric encryption

If i am not wrong in cryptography there are 2 basic cryptographic schemes for public key cryptography. RSA encryption whose security is based on the infeasibility of solving the factoring of big primes problem and the ElGamal encryption which is as…
curious
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Advantages using Diffie-Hellman or ElGamal

For what kind of usage should we prefer using Diffie-Hellman in order to exchange keys instead of ElGamal, and most important why should we use one or the other? I do not see a clear difference between these two algorithms. What are their respective…
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Are any of the major asymmetric ciphers distinguishable (EG, RSA, ECC)?

Related to "Is it possible to derive the encryption method from encrypted text?". Given ciphertexts generated by any of the major asymmetric ciphers (RSA, ElGamal, ECC, etc..) can these ciphertexts be distinguished from random noise? Justify why,…
Ethan Heilman
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ElGamal: Multiplicative cyclic group and key generation

Here on the ElGamal wikipedia page http://en.wikipedia.org/wiki/ElGamal_encryption Alice generates an efficient description of a multiplicative cyclic group G, of order q, with generator g. How is this done? What are some of the properties here?
Bobby S
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Difference between Pedersen commitment and commitment based on ElGamal

Does any of you know what is the difference between the Pedersen commitment and the commitment that uses the ElGamal encryption scheme? For the sake of completeness, I recall what both of them look like. Given two public and large primes $p$ and…
LRM
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Can Elgamal be made additively homomorphic and how could it be used for E-voting?

Elgamal is a cryptosystem that is homomorphic over multiplication. How can I convert it to an additive homomorphic cryptosystem? How can I use this additive homomorphic Elgamal cryptosystem for E-voting purpose? Please explain with examples.
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Mapping between subgroups and the integers

This question is a companion to the equivalent question on elliptic curves. Preliminaries Diffie-Hellman, Elgamal, DSA, etc. are examples of protocols that work in the integers modulus a large prime $p$. However, for security reasons, we do not use…
PulpSpy
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Mapping of message onto elliptic curve and reverse it?

I would like to perform a variant of Elliptic Curve ElGamal in java using the BouncyCastle libraries. I currently face the difficulty of mapping a message $m$ onto the elliptic curve $E_p$. I have so far multiplied the generator $g$ of $E_p$ by the…
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What is largest prime factor in Diffie-Hellman?

I was reading the paper of A Public Key Cryptosystem and a Signature Scheme Based on Discrete Logarithms by TAHER ELGAMAL to better understand ElGamal public-key scheme, and he stated that for any cryptosystem based on discrete logarithm problem,…
vxek
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Random Coin Flip using ElGamal and a Trusted Party

An old exam question I am trying to figure out: Consider the following protocol for two parties to flip a fair coin. Trusted party T publishes her public key pk A chooses a random bit $b_A$, encrypts it under pk, and announces the ciphertext…
Bobby S
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Why elgamal is still discussed

As I understand, if two users have a shared key, it is possible to encrypt a message using symmetric key encryption. So when a secret key is shared through Diffie-Hellman asymmetric key exchange, it means that the users have their shared key. So…
smslce
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How to create an EC point from a plaintext message for encryption

It seems that ElGamal encryption is also possible for Elliptic Curve cryptography. However, that requires the user to convert the message to a point on the curve. What strategies are there to derive a point from a plaintext message? Is it simply…
Maarten Bodewes
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ECIES/ ECDHE/ EC-ElGamal encryption comparison

I need to choose an encryption system, so I am trying to understand the differences between the existing options. I always find that people compare ECIES (Elliptic Curve Integrated Encryption Scheme) with RSA or ElGamal. It is clear that…
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How is a re-encryption done with elGamal?

For example, the "Mental poker" protocol asks for Bob to encrypt each card with his key, shuffle them, and then pass them to Alice. Alice then encrypts each card with HER key, shuffles them, and then hands them back. Bob removes his original key…
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