A Data Consistency Insurance Method for Smart Contract

As one of the major threats to the current DeFi(Decentralized Finance)ecosystem,reentrant attack induces data inconsistency of the victim smart contract,enabling attackers to steal on-chain assets from DeFi projects,which could terribly do harm to the confidence of the blockchain investors.However,protecting DeFi projects from the reentrant attack is very difficult,since generating a call loop within the highly automatic DeFi ecosystem could be very practicable.Existing researchers mainly focus on the detection of the reentrant vulnerabilities in the code testing,and no method could promise the non-existent of reentrant vulnerabilities.In this paper,we introduce the database lock mechanism to isolate the correlated smart contract states from other operations in the same contract,so that we can prevent the attackers from abusing the inconsistent smart contract state.Compared to the existing resolutions of front-running,code audit,andmodifier,our method guarantees protection resultswith better flexibility.And we further evaluate our method on a number of de facto reentrant attacks observed from Etherscan.The results prove that our method could efficiently prevent the reentrant attack with less running cost.

移动社交网络中基于代理转发机制的轨迹隐私保护方法

K匿名技术是当前轨迹隐私保护的主流方法,但该方法也存在隐私泄露的风险。该文提出一种在移动社交网络中基于代理转发机制(BAFM)的轨迹隐私保护方法。该方法利用安全多方计算和内积安全计算进行隐私加密匹配,通过可信服务器在移动社交网络中找最匹配的用户做代理,然后由代理转发用户的请求到服务器进行查询,隐藏用户的真实轨迹与位置服务器的联系,有效保护用户的轨迹隐私。安全分析表明该方法能有效保护用户的轨迹隐私;同时,通过实验验证该方法相对K匿名更高效,能减小服务器的查询和通信开销。

基于灰色马尔可夫模型的无线传感器网络目标跟踪算法

基于预测的目标跟踪是无线传感器网络目标定位与跟踪中很重要的一种方法,但在实际环境中由于目标运动模式的动态变化等原因,传统预测算法对目标位置的预测往往不准确。为了克服以上不足,提出了一种基于灰色马尔可夫模型的目标跟踪(GMMTT)算法。将具有震荡特点的Markov模型引入到分段灰色预测中,使目标定位既能获得较好的精度,又能适应目标运动模式的变化。预测得到目标位置后,当前跟踪节点将跟踪信息传送到目标下一时刻将要到达的预测区域,提前唤醒该区域内的节点,用尽可能少的节点实现目标有效的跟踪。实验结果表明:GMMTT算法在跟踪概率和跟踪精度方面具有较好的性能。