ElGamal encryption

About: ElGamal encryption is a research topic. Over the lifetime, 1218 publications have been published within this topic receiving 39753 citations.

A method for obtaining digital signatures and public-key cryptosystems

Abstract: An encryption method is presented with the novel property that publicly revealing an encryption key does not thereby reveal the corresponding decryption key. This has two important consequences: (1) Couriers or other secure means are not needed to transmit keys, since a message can be enciphered using an encryption key publicly revealed by the intented recipient. Only he can decipher the message, since only he knows the corresponding decryption key. (2) A message can be “signed” using a privately held decryption key. Anyone can verify this signature using the corresponding publicly revealed encryption key. Signatures cannot be forged, and a signer cannot later deny the validity of his signature. This has obvious applications in “electronic mail” and “electronic funds transfer” systems. A message is encrypted by representing it as a number M, raising M to a publicly specified power e, and then taking the remainder when the result is divided by the publicly specified product, n, of two large secret primer numbers p and q. Decryption is similar; only a different, secret, power d is used, where e * d ≡ 1(mod (p - 1) * (q - 1)). The security of the system rests in part on the difficulty of factoring the published divisor, n.

A new remote user authentication scheme using smart cards

Abstract: We propose a new remote user authentication scheme using smart cards. The scheme is based on the ElGamal's (1985) public key cryptosystem. Our scheme does not require a system to maintain a password table for verifying the legitimacy of the login users. In addition, our scheme can withstand message replaying attack.

Cross-VM side channels and their use to extract private keys

Abstract: This paper details the construction of an access-driven side-channel attack by which a malicious virtual machine (VM) extracts fine-grained information from a victim VM running on the same physical computer. This attack is the first such attack demonstrated on a symmetric multiprocessing system virtualized using a modern VMM (Xen). Such systems are very common today, ranging from desktops that use virtualization to sandbox application or OS compromises, to clouds that co-locate the workloads of mutually distrustful customers. Constructing such a side-channel requires overcoming challenges including core migration, numerous sources of channel noise, and the difficulty of preempting the victim with sufficient frequency to extract fine-grained information from it. This paper addresses these challenges and demonstrates the attack in a lab setting by extracting an ElGamal decryption key from a victim using the most recent version of the libgcrypt cryptographic library.

Selecting Cryptographic Key Sizes

Abstract: In this article we offer guidelines for the determination of key sizes for symmetric cryptosystems, RSA, and discrete logarithm-based cryptosystems both over finite fields and over groups of elliptic curves over prime fields. Our recommendations are based on a set of explicitly formulated parameter settings, combined with existing data points about the cryptosystems.

Traitor Tracing with Constant Transmission Rate

Abstract: An important open problem in the area of Traitor Tracing is designing a scheme with constant expansion of the size of keys (users' keys and the encryption key) and of the size of ciphertexts with respect to the size of the plaintext. This problem is known from the introduction of Traitor Tracing byChor, Fiat and Naor. We refer to such schemes as traitor tracing with constant transmission rate. Here we present a general methodologyand two protocol constructions that result in the first two public-keytraitor tracing schemes with constant transmission rate in settings where plaintexts can be calibrated to be sufficientlylarge. Our starting point is the notion of "copyrighted function" which was presented byNaccac he, Shamir and Stern. We first solve the open problem of discrete-log-based and public-key-based "copyrighted function." Then, we observe the simple yet crucial relation between (public-key) copyrighted encryption and (public-key) traitor tracing, which we exploit byin troducing a generic design paradigm for designing constant transmission rate traitor tracing schemes based on copyrighted encryption functions. Our first scheme achieves the same expansion efficiency as regular ElGamal encryption. The second scheme introduces only a slightlylarger (constant) overhead, however, it additionallyac hieves efficient black-box traitor tracing (against any pirate construction).