A high-resolution climatic change since Holocene inferred from multi-proxy of lake sediment in westerly area of China

Multi-proxy data are presented and a discuss is made of paleoclimatic and paleoenvironmental changes during Holocene from a 225-cm-long sediment core from Wulungu Lake, located in westerly area of China. The chronology is constructed from six AMS radiocarbon dates on the bulk organic matter. Analyses of pollen, TOC, TN, δ 13Corg, ostracod assemblages and the shell stable isotopes, suggest Holocene climate pattern as follows: temperate and dry (10.0―7.6 cal. ka BP)-warm and wet (7.6―5.3 cal. ka BP) -warm and moist (5.3―3.6 cal. ka BP) -temperate and dry (3.6―2.1 cal. ka BP)-temperate and moist (2.1―1.3 cal. ka BP) -cool and dry (1.3 cal. ka BP―present). With the climatic change, Wulungu Lake experienced two large-scale retreat (5.3―3.6 cal. ka BP and 1.3 cal. ka BP―present) and an obvious transgression (7.6―5.3 cal. ka BP). The records of climatic and environmental evolution of Wulungu Lake were in good accordance with those of adjacent areas. It responded to regional environmental change, global abrupt climate events and followed the westerly climate change mode.     

Efficient and secure multi-signature scheme based on trusted computing

A new multi-signature scheme was proposed with the extension of the direct anonymous attestation (DAA) protocol supported by trusted computing (TC) technology. Analysis and simulation results show that the signer’s privacy is well protected with dynamic anonymity, the public key and signatures have length independent of the number of signature members, new signers are allowed to join the signature without modifying the public key, and attacks caused by secret key dumping or leaking can be avoided. Biography: HAO Liming (1982–), male, Ph.D. candidate, research direction: trusted computing and trust management in P2P system.     

Multi-proxy quantum group signature scheme with threshold shared verification

A multi-proxy quantum group signature scheme with threshold shared verification is proposed. An original signer may authorize a proxy group as his proxy agent. Then only the cooperation of all the signers in the proxy group can generate the proxy signature on behalf of the original signer. In the scheme, any t or more of n receivers can verify the message and any t - 1 or fewer receivers cannot verify the validity of the proxy signature.     

一种改进的定向代理签名方案

在通常的代理签名方案中,任何人都可以验证代理签名的有效性。在定向代理签名方案中,由原始签名人指定一个人作为签名的接收者,以此来防止签名的滥用。当代理签名人产生签名后,只有指定的接收者可以对签名进行验证,进而接受签名。分析了Dai等定向代理签名方案,它不满足不可伪造性,即原始签名人可以成功伪造代理签名人的代理签名。为此,提出了改进的定向代理签名方案,该方案具有不可伪造性,从而有效地防止原始签名人对代理签名人进行恶意攻击,并将其推广到代理多签名方案中。     

前向安全的指定验证人代理多重签名方案

基于有限域上离散对数难解问题和强RSA假设,提出了一个前向安全的指定验证人代理多重签名方案.在方案中,代理签名人不仅可以代表多个原始签名人生成指定验证人的代理多重签名,确保只有原始签名人指定的验证人可以验证代理多重签名的有效性;而且在该方案中,代理多重签名是前向安全的,即使代理签名人当前时段的代理多重签名密钥被泄漏,敌手也不能伪造此时段之前的代理多重签名,以前所产生的代理多重签名依然有效.     

基于RSA的多元非对称密码系统在数字签名中的应用

在RSA密码系统上建立多元非对称密码系统， 并以此针 对多种签名形式设计多种签名方案.     

无证书的XML多重签名

针对XML电子公文流转系统中公文审批存在多重签名的需求,构建了两种新的XML多重签名研究模型.基于相应的研究模型,提出了一种无证书的XML有序多重签名方案和无证书的XML广播多重签名方案,以解决传统签名在此类应用中存在的签名效率低、可扩展性差等问题.同时分析了两种方案的正确性、在随机预言模型下的不可伪造性,而且无证书的XML有序多重签名方案,克服了已有方案相邻成员可以擅自交换签名顺序的缺点.最后,按照XML数字签名规范化要求,对多重签名的实现过程进行了设计,为XML多重签名在电子政务中的应用提供了可行的解决途径.     

一个前向安全的多重数字签名方案

将前向安全的概念引入基于RSA及哈希函数的多重数字签名体制,提出了一个前向安全的数字签名方案.方案能实现即使所有签名人的签名密钥被泄露,以前所产生的多重数字签名依然有效.另外,该方案引入了时间标志,在一定程度上抵抗重播攻击.     

典型代理多重签名方案的分析与改进

YBX代理多重签名方案是不安全的,攻击者在不知道原始签名者密钥的情况下,能够伪造代理签名密钥,假冒代理签名者对文件进行签名。在全面分析攻击方案的基础上,构造了一种增强的代理多重签名方案。新方案克服了YBX方案的代理转移、不具有强不可否认性等缺陷,除了具有普通签名方案的安全性外,还具有接收方可查的时控代理多重签名方案的性质。     

A Nominative Multi-Proxy Signature Scheme Based on ECC

A nominative multi proxy signature in which the original signer authorizes a group of proxy signers is presented. Meanwhile, our proposed scheme is based on elliptic curve cryptosystem which is more efficient than the corresponding one based on traditional discrete logarithm.