What is a semantically secure cipher?
From Wikipedia, the free encyclopedia. In cryptography, a semantically secure cryptosystem is one where only negligible information about the plaintext can be feasibly extracted from the ciphertext.
Is ElGamal encryption secure?
ElGamal encryption is provably secure under CPA [19], and is insecure under CCA2. It is conjectured to be secure under CCA1, but there has been no formal proof.
What mathematical problem is behind security of the ElGamal cryptosystem?
discrete log problem
In ElGamal, the underlying mathematical relationship between the encryption and decryption keys relies upon the so-called discrete log problem, which will be described a bit later.
What is ElGamal encryption algorithm?
In cryptography, the ElGamal encryption system is an asymmetric key encryption algorithm for public-key cryptography which is based on the Diffie–Hellman key exchange. It was described by Taher Elgamal in 1985.
Why is RSA not semantically secure?
Because RSA encryption is a deterministic encryption algorithm (i.e., has no random component) an attacker can successfully launch a chosen plaintext attack against the cryptosystem, by encrypting likely plaintexts under the public key and test if they are equal to the ciphertext.
Why ElGamal is secure?
Being a public key encryption algorithm, ElGamal algorithm depends on both the private and secret keys it generates to encrypt the data. Thus the main problem becomes securing and managing these keys. This security can be achieved by using certain hardware modules with key management software.
What is the main disadvantage of ElGamal compared to RSA?
The degree of difficulty in RSA lies in the factorization of large primes while in ElGamal lies in the calculation of discrete logarithms. After testing, it is proven that RSA performs a faster encryption process than ElGamal. However, ElGamal decryption process is faster than RSA.
Why is RSA not used for large messages?
Simply, RSA is very resource expensive algorithm, it takes time to generate RSA keys and to perform operations on these enormous prime numbers. As the size of data increases, the process load increases and the whole thing ends up taking too much time to complete.
Is RSA probabilistic?
Since the original RSA encryption scheme was not probabilistic, several padding techniques such as OAEP are considered so that the padded RSA scheme becomes probabilistic and satisfies security properties, such as semantic security.
What is the difference between chosen plaintext and chosen ciphertext?
The difference is how the plaintext-ciphertext pairs that the attacker has access to are generated. In a chosen plaintext attack, the attacker chooses some plaintext and is handed the corresponding ciphertext. In other words, the attacker may encrypt arbitrary messages.
What is semantically secure cryptography?
Semantic security. In cryptography, a semantically secure cryptosystem is one where only negligible information about the plaintext can be feasibly extracted from the ciphertext. Specifically, any probabilistic, polynomial-time algorithm (PPTA) that is given the ciphertext of a certain message (taken from any distribution of messages),…
What are the most secure encryption algorithms?
Semantically secure encryption algorithms include Goldwasser-Micali, ElGamal and Paillier. These schemes are considered provably secure, as their semantic security can be reduced to solving some hard mathematical problem (e.g., Decisional Diffie-Hellman or the Quadratic Residuosity Problem ).
How secure is asymmetric key encryption?
For an asymmetric key encryption algorithm cryptosystem to be semantically secure, it must be infeasible for a computationally bounded adversary to derive significant information about a message (plaintext) when given only its ciphertext and the corresponding public encryption key.
What is semantic security and perfect secrecy?
This concept is the computational complexity analogue to Shannon’s concept of perfect secrecy. Perfect secrecy means that the ciphertext reveals no information at all about the plaintext, whereas semantic security implies that any information revealed cannot be feasibly extracted.