A PKI without TTP based on conditional trust in blockchain
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GREEN AND HUMAN INFORMATION TECHNOLOGY 2019
A PKI without TTP based on conditional trust in blockchain KyungHyun Han1 • Seong Oun Hwang2 Received: 8 May 2019 / Accepted: 30 July 2019 Springer-Verlag London Ltd., part of Springer Nature 2019
Abstract Many people have used public keys in various areas based on public key infrastructure (PKI). PKI provides a method to publicize public keys securely. However, existing PKI methods have a problem that they assume trusted third parties. Therefore, the existing PKIs cannot be used when users cannot trust certificate issuers. To solve this problem, we propose a new trust model and describe its implementation based on blockchain. Users can trust the certificate issued by full nodes even if they do not trust the full nodes themselves. We analyze the security of our model and show that its security can be achieved higher than existing models. This new model can be particularly useful in an environment where a third party cannot be easily trusted. Keywords PKI Blockchain Trust model Certificate
1 Introduction In this modern era, there are two major encryption algorithms, which are symmetric key and asymmetric key cryptography. In the symmetric key cryptography, users use the same key for encryption and decryption. To prevent information leakage, the key must be kept as secret to both encrypting and decrypting parties only. Unfortunately, it is difficult for two or more parties that did not share any information to agree to the same secret in symmetric cryptography. In contrast, pairs of keys are used in asymmetric key cryptography, where private keys are kept secret by owners and their corresponding public keys are disseminated publicly. Therefore, it becomes easier to share keys among users in asymmetric key cryptography than in symmetric key cryptography. Therefore, asymmetric key cryptography has been widely used for digital signature as well as encryption.
& Seong Oun Hwang [email protected] KyungHyun Han [email protected] 1
Department of Electronics and Computer Engineering, Graduate School of Hongik University, Sejong, Korea
2
Department of Software and Communications Engineering, Hongik University, Sejong, Korea
However, sharing the public keys in asymmetric cryptography still raises a problem. That is, it is difficult for the receiver of a public key to believe that the received key is the right public key of the sender, because it may be possible for a sender to send a public key with wrong identity or for someone else to modify the public key or the sender’s information in the middle. To use public key securely, public key infrastructure (PKI) is necessary. PKI provides a function that binds a public key with its owner. Most of the currently used public keys are shared under the control of the PKI. Certificate authority (CA) and web of trust (WoT) are popularly used methods for PKI in the real world. But all of these models have a problem in common with trust. For example, CA assumes a trusted th
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