In Shamir’s(t,n) threshold of the secret sharing scheme, a secret is divided into n shares by a dealer and is shared among n shareholders in such a way that (a) the secret can be reconstructed when there are t or mor...In Shamir’s(t,n) threshold of the secret sharing scheme, a secret is divided into n shares by a dealer and is shared among n shareholders in such a way that (a) the secret can be reconstructed when there are t or more than t shares;and (b) the secret cannot be obtained when there are fewer than t shares. In the secret reconstruction, participating users can be either legitimate shareholders or attackers. Shamir’s scheme only considers the situation when all participating users are legitimate shareholders. In this paper, we show that when there are more than t users participating and shares are released asynchronously in the secret reconstruction, an attacker can always release his share last. In such a way, after knowing t valid shares of legitimate shareholders, the attacker can obtain the secret and therefore, can successfully impersonate to be a legitimate shareholder without being detected. We propose a simple modification of Shamir’s scheme to fix this security problem. Threshold cryptography is a research of group-oriented applications based on the secret sharing scheme. We show that a similar security problem also exists in threshold cryptographic applications. We propose a modified scheme to fix this security problem as well.展开更多
（k, n） halftone visual cryptography （HVC） is proposed based on Shamir＇ s secret sharing （HVCSSS）, and through this method a binary secret image can be hided into n halftone images, and the secret image can be r...（k, n） halftone visual cryptography （HVC） is proposed based on Shamir＇ s secret sharing （HVCSSS）, and through this method a binary secret image can be hided into n halftone images, and the secret image can be revealed from any k halftone images. Firstly, using Shamir＇ s secret sharing, a binary secret image can be shared into n meaningless shares; secondly, hiding n shares into n halftone images through self-hiding method; and then n extracted shares can be obtained from n halftone images through self-decrypt method; finally, picking any k shares from n extracted shares, the secret image can be revealed by using Lagrange interpolation. The main contribution is that applying Shamir＇ s secret sharing to realize a （k, n） HVC, and this method neither requires code book nor suffers from pixel expansion. Experimental results show HVCSSS can realize a （k, n） HVC in gray-scale and color halftone images, and correct decoding rate （CDR） of revealed secret image can be guaranteed.展开更多
利用拉格朗日插值多项式的不同构造方法,提出了可实现单幅或多幅图像秘密共享的(r,n)门限方案.解决了图像共享过程中诸如图像质量损失以及恢复秘密时的防欺诈等问题,并成功地将应用于灰度图像的方案相应地扩展到彩色图像上.利用该方案,...利用拉格朗日插值多项式的不同构造方法,提出了可实现单幅或多幅图像秘密共享的(r,n)门限方案.解决了图像共享过程中诸如图像质量损失以及恢复秘密时的防欺诈等问题,并成功地将应用于灰度图像的方案相应地扩展到彩色图像上.利用该方案,在有图像质量损失的情况下,恢复图像的PPSNR(Peaks of theSignal-to-Noise Ratio)值均大于30 dB,而无质量损失情况下,恢复图像与原图相同.给出了实验结果和一些参数在特殊取值时的分析结果,提出了在实际共享图像时选取参数的建议.该方案在对共享图像质量有较高要求的场合有一定实用价值.展开更多
文摘In Shamir’s(t,n) threshold of the secret sharing scheme, a secret is divided into n shares by a dealer and is shared among n shareholders in such a way that (a) the secret can be reconstructed when there are t or more than t shares;and (b) the secret cannot be obtained when there are fewer than t shares. In the secret reconstruction, participating users can be either legitimate shareholders or attackers. Shamir’s scheme only considers the situation when all participating users are legitimate shareholders. In this paper, we show that when there are more than t users participating and shares are released asynchronously in the secret reconstruction, an attacker can always release his share last. In such a way, after knowing t valid shares of legitimate shareholders, the attacker can obtain the secret and therefore, can successfully impersonate to be a legitimate shareholder without being detected. We propose a simple modification of Shamir’s scheme to fix this security problem. Threshold cryptography is a research of group-oriented applications based on the secret sharing scheme. We show that a similar security problem also exists in threshold cryptographic applications. We propose a modified scheme to fix this security problem as well.
基金supported by the National Natural Science Foundation of China(61370188)the Scientific Research Common Program of Beijing Municipal Commission of Education(KM201610015002,KM201510015009)+2 种基金the Beijing City Board of Education Science and Technology Key Project(KZ201510015015,KZ201710015010)Project of Beijing Municipal College Improvement Plan(PXM2017_014223_000063)BIGC Project(Ec201802,Ed201803,Ea201806)
文摘（k, n） halftone visual cryptography （HVC） is proposed based on Shamir＇ s secret sharing （HVCSSS）, and through this method a binary secret image can be hided into n halftone images, and the secret image can be revealed from any k halftone images. Firstly, using Shamir＇ s secret sharing, a binary secret image can be shared into n meaningless shares; secondly, hiding n shares into n halftone images through self-hiding method; and then n extracted shares can be obtained from n halftone images through self-decrypt method; finally, picking any k shares from n extracted shares, the secret image can be revealed by using Lagrange interpolation. The main contribution is that applying Shamir＇ s secret sharing to realize a （k, n） HVC, and this method neither requires code book nor suffers from pixel expansion. Experimental results show HVCSSS can realize a （k, n） HVC in gray-scale and color halftone images, and correct decoding rate （CDR） of revealed secret image can be guaranteed.
文摘利用拉格朗日插值多项式的不同构造方法,提出了可实现单幅或多幅图像秘密共享的(r,n)门限方案.解决了图像共享过程中诸如图像质量损失以及恢复秘密时的防欺诈等问题,并成功地将应用于灰度图像的方案相应地扩展到彩色图像上.利用该方案,在有图像质量损失的情况下,恢复图像的PPSNR(Peaks of theSignal-to-Noise Ratio)值均大于30 dB,而无质量损失情况下,恢复图像与原图相同.给出了实验结果和一些参数在特殊取值时的分析结果,提出了在实际共享图像时选取参数的建议.该方案在对共享图像质量有较高要求的场合有一定实用价值.
