Abstract. NEON is a vector instruction set included in a large fraction of new ARM-based tablets and smartphones. This paper shows that NEON supports high-security cryptography at surprisingly high speeds; normally data arrives at lower speeds, giving the CPU time to handle tasks other than cryptography. In particular, this paper explains how to use a single 800MHz Cortex A8 core to compute the existing NaCl suite of high-security cryptographic primitives at the following speeds: 5.60 cycles per byte (1.14 Gbps) to encrypt using a shared secret key, 2.30 cycles per byte (2.78 Gbps) to authenticate using a shared secret key, 527102 cycles (1517/second) to compute a shared secret key for a new public key, 650102 cycles (1230/second) to verify a signature, and 368212 cycles (2172/second) to sign a message. These speeds make no use of secret branches and no use of secret memory addresses.

. This paper is an introduction to cryptography. It covers secretkey message authentication codes, unpredictable random functions, public-key secret-sharing systems, and public-key signature systems. 1.

The popularity of personal computing devices (e.g. smart cards) exposes users to risks, notably identity theft, and creates new requirements for secure communication. A recently proposed approach to creating secure communication is to use human trust and human interactions. These approaches potentially eliminate the need for passwords as in Bluetooth, shared secrets or trusted parties, which are often too complex and expensive to use in portable devices. In this new technology, handheld devices exchange data (e.g. payment, heart rates or public keys) over some medium (e.g. WiFi) and then display a short and non-secret digest of the protocol’s run that the devices ’ human owners manually compare to ensure they agree on the same data, i.e. human interactions are used to prevent fraud. In this thesis, we present several new protocols of this type which are designed to optimise the work required of humans to achieve a given level of security. We discover that the design of these protocols is influenced by several principles, including the ideas of commitment without knowledge and separation of security concerns, where random and cryptographic attacks should be tackled separately.

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