Abstract. In this paper, we report that we have solved the SVP Challenge over a 128-dimensional lattice in Ideal Lattice Challenge from TU Darmstadt, which is currently the highest dimension in the challenge that has ever been solved. The security of lattice-based cryptography is based on the hardness of solving the shortest vector problem (SVP) in lattices. In 2010, Micciancio and Voulgaris proposed a Gauss Sieve algorithm for heuristically solving the SVP using a list L of Gaussreduced vectors. Milde and Schneider proposed a parallel implementation method for the Gauss Sieve algorithm. However, the efficiency of the more than 10 threads in their implementation decreased due to the large number of non-Gauss-reduced vectors appearing in the distributed list of each thread. In this paper, we propose a more practical parallelized Gauss Sieve algorithm. Our algorithm deploys an additional Gauss-reduced list V of sample vectors assigned to each thread, and all vectors in list L remain Gauss-reduced by mutually reducing them using all sample vectors in V . Therefore, our algorithm allows the Gauss Sieve algorithm to run for large dimensions with a small communication overhead. Finally, we succeeded in solving the SVP Challenge over a 128-dimensional ideal lattice generated by the cyclotomic polynomial x 128 + 1 using about 30,000 CPU hours.

In this paper, we propose new attacks on 9-round Salsa20 and 8-round ChaCha. We constructed a distinguisher of double-bit di«erentials to improve Aumasson's single-bit di«erential cryptanalysis. We searched for correlations using a PC, and found strong correlations in 9-round Salsa20 and 8-round ChaCha. The complexities of the introduced attacks are 2 16 in 9-round Salsa20 and 2 in 8-round ChaCha, which are much less than the complexities of an exhaustive key search and existing attacks on those ciphers. The results show that an adversary can distinguish keystream bits from random bits using a few input and output pairs of an initial keys and initial vectors. This method has potential to apply to a wide range of stream ciphers; a double-bit correlation would be found in case that no single-bit correlation is found.

Web Workers is a specification that defines an API which allows Web application developers to use background workers running scripts in parallel. Web Workers is used with JavaScript and is platform-independent. Hence, Web applications written in JavaScript can be used for a wide variety of purposes. There are many Web applications and some of them, for instance Internet election campaign and real-time broadcasting, need secure communications. We can include digital signatures with such Web applications to guarantee their security of communications. In this demonstration proposal, we assess the performance of parallel implementations of public key cryptosystems on several Web browsers (Internet Explorer, Google Chrome, Opera, and Firefox). With our implementation, it is possible to verify a message in 1.03 milliseconds on a Windows PC and 5.49 milliseconds on an Android tablet (Nexus 7). We also propose cryptography applications for Web browsers.

KCipher-2 is a word-oriented stream cipher and an ISO/IEC 18033 standard. It is listed as a CRYPTREC cryptographic algorithm for Japanese governmental use. It consists of two feedback shift registers and a non-linear function. The size of each register in KCipher-2 is 32 bits and the non-linear function mainly applies 32-bit operations. Therefore, it can be efficiently implemented as software. SNOW-family stream ciphers are also word-oriented stream ciphers, and their high performance has already been demonstrated. We propose optimised implementations of KCipher-2 and compare their performance to that of the SNOW-family and other eSTREAM portfolios. The fastest algorithm is SNOW 2.0 and KCipher-2 is the second fastest despite the complicated irregular clocking mechanism. However, KCipher-2 is the fastest of the feasible algorithms, as SNOW 2.0 has been shown to have a security flaw. We also optimise the hardware implementation for the Virtex-5 field-programmable gate array (FPGA) and show two implementations. The first implementation is a rather straightforward optimisation and achieves 16,153 Mbps with 732 slices. In the second implementation, we duplicate the non-linear function using the structural advantage of KCipher-2 and we achieve 17,354 Mbps with 813 slices. Our implementation of KCipher-2 is around three times faster than those of the SNOW-family and efficiency, which is evaluated by "Throughput/Area (Mbps/slice)", is 3.6-times better than that of SNOW 2.0 and 8.5-times better than that of SNOW 3G. These syntheses are performed using Xilinx ISE version 12.4.

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