CBC MACs for Arbitrary-Length Messages: The Three-Key Constructions

We suggest some simple variants of the CBC MAC that enable the efficient authentication of arbitrary-length messages. Our constructions use three keys, K1, K2, K3, to avoid unnecessary padding and MAC any message M {0,1}* using max{1, |M|/n} applications of the underlying n-bit block cipher. Our favorite construction, XCBC, works like this: if |M| is a positive multiple of n then XOR the n-bit key K2 with the last block of M and compute the CBC MAC keyed with K1; otherwise, extend Ms length to the next multiple of n by appending minimal 10 padding ( 0), XOR the n-bit key K3 with the last block of the padded message, and compute the CBC MAC keyed with K1. We prove the security of this and other constructions, giving concrete bounds on an adversarys inability to forge in terms of his inability to distinguish the block cipher from a random permutation. Our analysis exploits new ideas which simplify proofs compared with prior work.     

Attacks on Fast Double Block Length Hash Functions

The security of hash functions based on a block cipher with a block length of m bits and a key length of k bits, where , is considered. New attacks are presented on a large class of iterated hash functions with a 2m -bit hash result which processes in each iteration two message blocks using two encryptions. In particular, the attacks break three proposed schemes: Parallel-DM, the PBGV hash function, and the LOKI DBH mode. Received 1 March 1996 and revised 16 December 1996     

基于消息认证函数的云端数据完整性检测方案

针对云计算中数据完整性问题,该文提出了一个新的交互式完整性检测方案。该方案通过构造一个I型完善Cartesian消息认证函数及其等效函数,在同步存储数据验证值的前提下,利用等效函数判定云端应答的消息认证值来检测完整性。分析结果表明,该方案在大数分解的困难性假设下能正确检测完整性,并且运行时仅需用户端常量的计算量、存储占用量和网络通信量,相比较现有方案,具有明显效率优势。     

块三对角线性方程组的可扩展块分割奇偶约化并行近似求解方法

文章对于一类严格块对角占优的块三对角线性方程组提出一个可扩展的块分割奇偶约化并行近似求解方法（PBOERA方法）。计算量减少到O（nm^2）＋O（m^3logm）;通信复杂度为常数。本方法在上海大学分布式并行计算机“自强3000”上使用64个节点进行了运行。得到线性加速比,并行效率达到90％以上。     

用于H.264/AVC的D级数据重用整数运动估计VLSI结构

本文提出了一种用于H.264/AVC的D级数据重用整数运动估计VLSI结构.提出的结构是在一种固定块尺寸运动估计VLSI结构基础上,利用交叉网络实现变块尺寸的计算,使用多bank的存储器组织方式,使片上存储器的读写规则简单,易于处理不同搜索范围和不同尺寸的视频的运动估计.提出的运动估计结构用Verilog HDL描述,使用HJTC 0.18μm工艺,用Synopsys DC做了逻辑综合.相比现有结构,该结构由于增加片上存储器,因此数据重用率高,大大降低了存储带宽需求;另外数据吞吐率高,能够满足高性能视频编码需求.     

Design Criteria for Non-Orthogonal Space–Time Block Codes in Multipath Channels

We consider the problem of designing high rate space–time block codes in multipath fading channels. For this, both minimizing the effect of the self-interference induced by the code itself, and mitigating the inter-symbol-interference induced by the channel have to be addressed. We translate the problem into an equivalent problem of designing a constrained code in a single-path channel with more antennas, and argue that design criteria derived in single-path apply when optimizing this constrained code. Here we concentrate on an analytic measure pertinent to mutual information maximization and BER-performance optimization. The design program is successfully applied to rate one linear space–time transmissions from four transmit antennas. A family of discrete permutations of the transmitted sequences are considered. Performance is optimized within this family, and the results are seen to effect directly both mutual information and error performance.