Dynamic Threshold Proxy-Protected Signature Scheme

• Main Authors: Chung-Hsien Tsai, 蔡崇賢
• Other Authors: Wei-Bin Lee
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/22492066651981433611

碩士 === 逢甲大學 === 資訊工程所 === 94 === Digital signature is a mechanism to protect digital documents in electronic generation nowadays. However, according to the application of the actual circumstances, the original signer may wish to delegate the power of signing message to a designated proxy signer in some conditions. This solves the problem if the original signer is traveling. In order to reduce risk, the original signer may delegate the power of signing messages to several designate proxy signers. When the proxy signers achieve a certain number to approve the contents of the digital document, they will be able to sign the digital document. For this reason, the threshold proxy signature has been developed. In (t, n) threshold proxy signature, the original signer delegates the power of signing messages to a proxy group with n designated proxy signers. Any t or more proxy signers of the group can cooperatively issue a proxy signature on behalf of the original signer, but (t-1) or less proxy signers cannot. However, security requirements of individual digital documents vary often in actual applications. When higher document security is required, the number of proxy signers in the proxy group should be increased. On the other hand, a lower number of proxy signers are required in order to achieve higher efficiency. In the past, the threshold value t of the proxy signers must decide at the beginning. No flexibility is provided. In this paper, we proposed a new scheme to solve this problem. We can announce the parameters to change the threshold value t. Once the combined proxy signers of threshold value t and announcing parameters that can generate a legal proxy signature, this result can enable the security to increase or reduce the threshold value flexibility. Additionally, this method can let each proxy signer create their own proxy signing key. Original signer does not need to use a secure channel to submit the partial proxy signing key. Therefore, the new scheme provides an easy and convenient way to delegate the power of digitally signed documents.