Chapter 8 has described several of the classical models of cryptography in which the decryption key was the same as or easily derivable from the encryption key. This meant that the corresponding encryption and decryption algorithms were closely related in the sense that one could be easily deduced from the other. Such cryptographic systems are called symmetric-key or conventional systems, and t...

Quantum key distribution (QKD) protocols make it possible for two quantum parties to generate a secret shared key. Semiquantum key distribution (SQKD) protocols, such as “QKD with classical Bob” and “QKD with classical Alice” (that have both been proven robust), achieve this goal even if one of the parties is classical. However, existing SQKD protocols are not experimentally feasible with curre...

We show that any encryption/decryption system can be converted to an algorithm which uses roughly three machine operations per bit. We prove that our technique yields an encryption/decryption system which is as secure as the original system provided the plaintext has full-entropy. We then show how to remove the full-entropy assumption. Our techniques speed up software implementations of RSA by ...

An analogue of McEliece’s cryptosystem, the Gabidulin-Paramonov-Trejtakov (GPT) public-key cryptosystem is based on rank-metric-based Gabidulin codes instead of Goppa codes. The GPT cryptosystem has attracted steady attention since it is much more robust against the decoding attacks and can therefore achieve the same level of security with much smaller keys. The key sizes, nonetheless, may stil...

In this paper, we analyze how key compromise affects the protocol by Nguyen et al. presented at ESORICS 2016, an authenticated key agreement protocol mediated by a proxy entity, restricted to only symmetric encryption primitives and intended for IoT environments. This protocol uses long-term encryption tokens as intermediate values during encryption and decryption procedures, which implies that...

Chosen-plaintext attacks on private-key encryption schemes are currently modeled by giving an adversary access to an oracle that encrypts a given message m using random coins that are generated uniformly at random and independently of anything else. This leaves open the possibility of attacks in case the random coins are poorly generated (e.g., using a faulty random number generator), or are un...

Encryption that is only semantically secure should not be used on messages that depend on the underlying secret key; all bets are off when, for example, one encrypts using a shared key K the value K. Here we introduce a new notion of security, KDM security, appropriate for key-dependent messages. The notion makes sense in both the public-key and shared-key settings. For the latter we show that ...

Multicast is an efficient technique to distribute data to a large group of users. To prevent disclosure of distributed data to unauthorized users, multicast-based applications require confidential group communication, which is achieved by encrypting data with a group-wide shared key. The group key must be updated and redistributed to all authorized users in a secure and reliable fashion wheneve...

Ciphers can be classified into two groups, based on the nature of the key. The family we’ll be talking about is symmetric-key the same key is used to encrypt and decrypt the data. There is a second family, called asymmetric-key cryptography. In assymetric key cryptography, the sender uses one key to encrypt and second to decrypt. Discussion and analysis of assymetric-key cryptography is beyond ...

Because of the resource-constrained nature of Wireless Sensor Networks (WSNs), it is easier to use a security system based on symmetric key cryptography. However, the distribution and management of cryptographic keys pose challenges of their own. In this paper, we study some deterministic methods of distribution of keys to nodes. We propose and analyze a polynomial-based scheme and a complete c...