Modern processors use branch prediction and speculative execution to maximize performance. For example, if the destination of a branch depends on a memory value that is in the process of being read, CPUs will try guess the destination and attempt to execute ahead. When the memory value finally arrives, the CPU either discards or commits the speculative computation. Speculative logic is unfaithful in how it executes, can access to the victim's memory and registers, and can perform operations with measurable side effects.Spectre attacks involve inducing a victim to speculatively perform operations that would not occur during correct program execution and which leak the victim's confidential information via a side channel to the adversary. This paper describes practical attacks that combine methodology from side channel attacks, fault attacks, and return-oriented programming that can read arbitrary memory from the victim's process. More broadly, the paper shows that speculative execution implementations violate the security assumptions underpinning numerous software security mechanisms, including operating system process separation, static analysis, containerization, just-in-time (JIT) compilation, and countermeasures to cache timing/side-channel attacks. These attacks represent a serious threat to actual systems, since vulnerable speculative execution capabilities are found in microprocessors from Intel, AMD, and ARM that are used in billions of devices.While makeshift processor-specific countermeasures are possible in some cases, sound solutions will require fixes to processor designs as well as updates to instruction set architectures (ISAs) to give hardware architects and software developers a common understanding as to what computation state CPU implementations are (and are not) permitted to leak. * After reporting the results here, we were informed that our work partly overlaps the results of independent work done at Google's Project Zero.

Abstract. We describe a public-key encryption system that remains secure even encrypting messages that depend on the secret keys in use. In particular, it remains secure under a "key cycle" usage, where we have a cycle of public/secret key-pairs (pk i , ski) for i = 1, . . . , n, and we encrypt each ski under pk (i mod n)+1 . Such usage scenarios sometimes arise in key-management systems and in the context of anonymous credential systems. Also, security against key cycles plays a role when relating "axiomatic security" of protocols that use encryption to the "computational security" of concrete instantiations of these protocols. The existence of encryption systems that are secure in the presence of key cycles was wide open until now: on the one hand we had no constructions that provably meet this notion of security (except by relying on the random-oracle heuristic); on the other hand we had no examples of secure encryption systems that become demonstrably insecure in the presence of key-cycles of length greater than one. Here we construct an encryption system that is circular-secure against chosen-plaintext attacks under the Decision Diffie-Hellman assumption (without relying on random oracles). Our proof of security holds even if the adversary obtains an encryption clique, that is, encryptions of ski under pk j for all 1 ≤ i, j ≤ n. We also construct a circular counterexample: a one-way secure encryption scheme that breaks completely if an encryption cycle (of any size) is published.

Lessons learned from Meltdown's exploitation of the weaknesses in today's processors.

Abstract. We provide a general framework for constructing identitybased and broadcast encryption systems. In particular, we construct a general encryption system called spatial encryption from which many systems with a variety of properties follow. The ciphertext size in all these systems is independent of the number of users involved and is just three group elements. Private key size grows with the complexity of the system. One application of these results gives the first broadcast HIBE system with short ciphertexts. Broadcast HIBE solves a natural problem having to do with identity-based encrypted email.

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This memo specifies two elliptic curves over prime fields that offer a high level of practical security in cryptographic applications, including Transport Layer Security (TLS). These curves are intended to operate at the ˜128-bit and ˜224-bit security level, respectively, and are generated deterministically based on a list of required properties.

Identity Based Encryption (IBE) systems are often constructed using bilinear maps (a.k.a. pairings) on elliptic curves. One exception is an elegant system due to Cocks which builds an IBE based on the quadratic residuosity problem modulo an RSA composite N . The Cocks system, however, produces long ciphertexts. Since the introduction of the Cocks system in 2001 it has been an open problem to construct a space efficient IBE system without pairings. In this paper we present an IBE system in which ciphertext size is short: an encryption of an -bit message consists of a single element in Z/N Z plus + 1 additional bits. Security, as in the Cocks system, relies on the quadratic residuosity problem. The system is based on the theory of ternary quadratic forms and as a result, encryption and decryption are slower than in the Cocks system.

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