The verifiable computation paradigm has been studied extensively as a means to verifying the result of outsourced computation. In said scheme, the verifier requests computation from the prover and verifies the result by checking the output and proof received from the prover. Although they have great potential for various critical applications, verifiable computations have not been widely used in practice, because of their significant performance overhead. Existing cryptography-based approaches incur significant overhead, because a cryptography-based mathematical frame needs to be constructed, which prevents deviation from the correct computation. The proposed approach is to reduce the overhead by trusting the computing hardware platform where the computation is outsourced. If one trusts the hardware to do the computation, the hardware can take the place of the cryptographic computing frame, thereby guaranteeing correct computation. The key challenge of this approach is to define what exactly the hardware should guarantee for verifiable computation. For this, we introduce the concept of Correct Execution Environment (CEE), which guarantees instruction correctness and state preservation. We prove that these two requirements are satisfactory conditions for a correct output. By employing a CEE, the verifiable computation scheme can be simplified, and its overhead can be reduced drastically. The presented experimental results demonstrate that the execution time is approximately 1.7 million times faster and the verification time over 50 times faster than a state-of-the-art cryptographic approach.

A forward secure identity based signature scheme (FSIBS) provides forward secrecy of secret keys. In order to mitigate the damage when keys are leaked, it is desirable to evolve all the secret keys, i.e., both the user keys and the master key. In this paper, we propose a new RSA-based FSIBS scheme which requires constant size keys and generates constant size signatures. The experimental results show that it takes 3ms to generate a signature in the proposed scheme while it takes 75ms in the existing pairing based approach. The proposed scheme is provably secure under the factoring assumption in the random oracle model.

With the rapid growth of the blockchain market, privacy and security issues for digital assets are becoming more important. In the most widely used public blockchains, such as Bitcoin and Ethereum, all activities on user accounts are publicly disclosed, which violates privacy regulations such as EU GDPR. Encryption of accounts and transactions may protect privacy, but it also raises issues of validity and transparency. While encrypted information can protect privacy, it cannot alone verify the validity of a transaction. Additionally, encryption makes it difficult to meet anti-money laundering regulations, such as auditability. In this paper, we propose Azeroth, an auditable zero-knowledge transfer framework. Azeroth connects a zero-knowledge proof to an encrypted transaction, enabling it to check its validation while protecting its privacy. Azeroth also allows authorized auditors to audit transactions. Azeroth is designed as a smart contract for flexible deployment on existing blockchains. We implement the Azeroth smart contract, and execute it on various platforms including an Ethereum testnet blockchain, and measure the time to show the practicality of our proposal. The end-to-end latency of a privacy-preserving transfer takes about 4.4s. In particular, the client's transaction generation time with a proof only takes about 0.9s. The security of Azeroth is proven under the cryptographic assumptions.INDEX TERMS Blockchain application, zero-knowledge proof, SNARK, privacy-preserving payment.