基于区块链的结果可追溯的可搜索加密方案

在可搜索加密方案中,无论是云端服务器还是用户,都可能存在欺骗行为。为了解决这种安全问题,给出公平性安全的定义,提出基于区块链的可搜索加密方案。通过第三方可信机构(trusted authority,TA)验证数据传输过程中数据的一致性,区块链记录完整验证结果以防止篡改,使所涉及的实体达成一致的安全共识,从而实现公平性安全。安全性与复杂性分析表明,该方案是可行的。当该方案与搜索结果可验证的可搜索加密方案相结合时,可优化成基于区块链的搜索结果可验证的可搜索加密方案,其安全性将得到进一步的提高。

语言测试中的技术应用:基于大学英语四、六级考试的实践分析

本文基于对大学英语四、六级考试中技术应用的梳理,阐述了技术应用对语言测试实践的影响。作者回顾了技术在大学英语四、六级考试三十多年发展历程中所发挥的作用,并以计算机化口语考试、自动评分系统和多题多卷模式为案例,分析了技术在完善四、六级考试的设计和实施、阅卷和评分以及安全和公平性等方面所体现的价值。基于案例分析,作者提出了大规模语言测试实践中的技术应用价值评价指标体系,探讨技术应用对考试效度、效率以及安全和公平性等方面所可能产生的影响。

Key substitution attacks on some verifiably encrypted signature schemes

As a special kind of digital signature, verifiably encrypted signatures are used as a building block to construct optimistic fair exchange. Many verifiably encrypted signature schemes have been proposed so far and most of them were proven secure under certain complexity assumptions. In this paper, however, we find that although some schemes are secure in a single-user setting, they are not secure in a multi-user setting any more. We show that Zhang, et al. ＇ s scheme, Gorantla, et al. ＇ s scheme and Ming, et al. ＇ s scheme are vulnerable to key substitution attacks, where an adversary can generate new keys satisfying legitimate verifiably encrypted signatures created by the legitimate users. We also show that this kind of attacks can breach the fairness when they are used in fair exchange in a multi-user setting.