A Blockchain-Based Decentralized Public Key Infrastructure Using the Web of Trust

Modern Internet TCP uses Secure Sockets Layers (SSL)/Transport Layer Security (TLS) for secure communication, which relies on Public Key Infrastructure (PKIs) to authenticate public keys. Conventional PKI is done by Certification Authorities (CAs), issuing and storing Digital Certificates, which are public keys of users with the users identity. This leads to centralization of authority with the CAs and the storage of CAs being vulnerable and imposes a security concern. There have been instances in the past where CAs have issued rogue certificates or the CAs have been hacked to issue malicious certificates. Motivated from these facts, in this paper, we propose a method (named as Trustful), which aims to build a decentralized PKI using blockchain. Blockchains provide immutable storage in a decentralized manner and allows us to write smart contracts. Ethereum blockchain can be used to build a web of trust model where users can publish attributes, validate attributes about other users by signing them and creating a trust store of users that they trust. Trustful works on the Web-of-Trust (WoT) model and allows for any entity on the network to verify attributes about any other entity through a trusted network. This provides an alternative to the conventional CA-based identity verification model. The proposed model has been implemented and tested for efficacy and known major security attacks.

The traditional public key infrastructure (PKI) issues certificates by trusted certification authority (CA). But due to the centralized structure of CA, it brings some problems, such as single-point failure, certificate opacity and so on. Another decentralized system web of trust (WOT) has a high access threshold. In addition, WOT cannot ensure the authenticity of users’ authentication because of lack of incentive, and it cannot authenticate the specific user identity. In this paper, we propose a new distributed identification system based on blockchain, called VAPKI. This system is implemented through smart contracts on Ethereum, which is transparent and immutable. Meanwhile, it can authenticate the fine-grained attributes of user identity and strengthen the authenticity of user identity through transparent authentication. In addition, VAPKI can identify the malicious user through the regular validation tasks (RVTs). In addition, it realizes the credit and deposit mechanism, ensuring users to be honest and trustworthy. This mechanism can also force users to authenticate strictly and punish malicious users found in RVTs.

The current Internet web trust system is based on the traditional PKI system, to achieve the purpose of secure communication through the trusted third party. However, with the increase of network nodes, various problems appear in the centralization system of public key infrastructure (PKI). In recent years, in addition to cryptographic problems, attacks against PKI have focused on the single point of failure of certificate authority (CA). Although there are many reasons for a single point of failure, the purpose of the attack is to invalidate the CA. Thus a distributed authentication system is explored to provide a feasible solution to develop distributed PKI with the rise of the blockchain. Due to the automation and economic penalties of smart contracts, a PKI system is proposed based on smart contracts. The certificate chain was constructed in the blockchain, and a mechanism was adopted for auditing access to CA nodes in the blockchain. Experimental results show that security requirements of CA are met in this system.

The “web of trust” is one approach to the problem of trusted exchange of public keys in a public key security system. In a web of trust, individuals accept the bulk of the responsibility for identifying and authenticating each other and subsequently swapping their keys. This trust model is supported by some commercial products and some industry standards. The main alternative is the Public Key Infrastructure (PKI) where key holders are identified and authenticated by third‐party Certification Authorities (CAs). Rather than personally swapping keys, participants in a PKI obtain one another’s public keys from one or more CAs in the form of digital certificates. These two trust models have, for some time, been vying for selection internationally in both policy and commercial forums. In Australia, the debate has been spurred on by recent deliberations over the possible form of a national peak authentication body, and by spirited discussion of the privacy impacts of a national hierarchy. There appears to be a view emerging that a web of trust might be easier to constitute than a hierarchy and that it may be inherently less intrusive. On closer inspection, however, these promises prove to be unfounded. This paper discusses certain limitations of any web of trust model, with particular reference to scalability, uniform standards of identification, auditability, and the protection of personal identification data.

Public key distribution and device authentication remain the main security challenges in many systems and applications. Existing solutions are based on Public Key Infrastructures (PKI) backed by Certificate Authorities (CA) to validate the authenticity of the devices. However, distributing and provisioning certificates for each client showed to be impractical especially for Internet of Things (IoT) devices. In this paper we propose a distributed PKI (Public Key Infrastructure) platform based on the Ethereum Blockchain. It contains a decentralized key-store that holds the public keys of all devices, and includes a generic protocol for PSK (Pre-Shared Keys) distribution. PSK keys can then be used by PSK-based security protocols (TLS-PSK, DTLS-PSK, SRTP…) for securing the communication channel between two devices. This platform includes a client-side module, a public key management module configured on the server, and a smart contract software deployed on the Ethereum Blockchain network. This generic platform can be used by many applications for client and server authentication, data integrity, and secure peer to peer communications. Moreover, this promising system may potentially eliminate the trust requirement imposed by the existing PKI/CAs infrastructure on clients.

SummaryIn classical public‐key infrastructure (PKI), the certificate authorities (CAs) are fully trusted, and the security of the PKI relies on the trustworthiness of the CAs. However, recent failures and compromises of CAs showed that if a CA is corrupted, fake certificates may be issued, and the security of clients will be at risk. As emerging solutions, blockchain‐ and log‐based PKI proposals potentially solved the shortcomings of the PKI, in particular, eliminating the weakest link security and providing a rapid remedy to CAs' problems. Nevertheless, log‐based PKIs are still exposed to split‐world attacks if the attacker is capable of presenting two distinct signed versions of the log to the targeted victim(s), while the blockchain‐based PKIs have scaling and high‐cost issues to be overcome. To address these problems, this paper presents a secure and accountable transport layer security (TLS) certificate management (SCM), which is a next‐generation PKI framework. It combines the two emerging architectures, introducing novel mechanisms, and makes CAs and log servers accountable to domain owners. In SCM, CA‐signed domain certificates are stored in log servers, while the management of CAs and log servers is handed over to a group of domain owners, which is conducted on the blockchain platform. Different from existing blockchain‐based PKI proposals, SCM decreases the storage cost of blockchain from several hundreds of GB to only hundreds of megabytes. Finally, we analyze the security and performance of SCM and compare SCM with previous blockchain‐ and log‐based PKI schemes.

Most currently deployed public key infrastructures (PKIs) are hierarchically oriented and rely on a centralized design. Hierarchical PKIs may be appropriate solutions for many usage-scenarios, but there exists the viable alternative of the 'Web of Trust'. In a web of trust, each user of the system can choose for himself whom he elects to trust, and whom not. After contrasting the properties of web-of-trust based PKIs to those of hierarchical PKIs, an introduction to webs of trust and to quantitative trust calculations is given. The paper concludes with the presentation of an efficient, sub-exponential algorithm that allows heuristic computations of trust paths in a web of trust.

The security of most Internet applications relies on underlying public key infrastructures (PKIs) and thus on an ecosystem of certification authorities (CAs). The pool of PKIs responsible for the issuance and the maintenance of SSL certificates, called the Web PKI, has grown extremely large and complex. Herein, each CA is a single point of failure, leading to an attack surface, the size of which is hardly assessable. This paper approaches the issue if and how the attack surface can be reduced in order to minimize the risk of relying on a malicious certificate. In particular, we consider the individualization of the set of trusted CAs. We present a tool called Rootopia, which allows to individually assess the respective part of the Web PKI relevant for a user. Our analysis of browser histories of 22 Internet users reveals, that the major part of the PKI is completely irrelevant to a single user. On a per user level, the attack surface can be reduced by more than 90%, which shows the potential of the individualization of the set of trusted CAs. Furthermore, all the relevant CAs reside within a small set of countries. Our findings confirm that we unnecessarily trust in a huge number of CAs, thus exposing ourselves to unnecessary risks. Subsequently, we present an overview on our approach to realize the possible security gains.

Nowadays, existing public key infrastructures (PKIs) certificate authentication suffers from many security failures. Trusted certificate authorities (CAs) can issue a valid certificate for any domain name. Although CA is supposed to be trusted by a client if the certificate issued to the client links to the chain of trust (e.g., root CA or subordinate CA). By compromising any of the latter (e.g., root CAs or subordinate CAs) an attacker can jeopardize the security of the entire system. Moreover, third-party CAs have to be trusted by domain owners. Currently, the trust is not balanced among the entities involved in the certificate authentication and issuance process (i.e., CAs and domain owners). To counter this problem approaches such as Domain authentication name entity (DANE) and Certificate Authority Authorization (CAA) offer additional securities for domain authentication. However, these approaches depend upon DNS/DNSSEC infrastructure which requires complex requirements for deployment as well as the adoption rate has been low. In this paper, we design, implement a robust and scalable domain authentication scheme based on blockchain technology with privacy-preserving features for low-constrained devices (e.g., mobile, browser, and IoT devices). The proposed system records a set of trusted CAs each associated with a specific domain in the blockchain. That is, each CA has to first verify if it is trusted to perform the actual issuance process. We compare our scheme with existing authentication methods and show that it requires less storage capacity and low bandwidth to authenticate certificates than other methods.

In the public key infrastructure, the certification authority is fully trusted, and the security of the public key infrastructure depends on the trust of the certification authority; however, recent attacks and corruption on the certification authority indicate that the certificate is forged when the certification authority fails . New solutions, blockchain-based public key infrastructure products and registry can repair vulnerabilities in public key infrastructure, especially weaker security systems. Proposals for infrastructure-based public key infrastructure. Public keys are still the target of global attacks. According to the registration of the target victim, it is signed as a temporary public key infrastructure based on the blockchain. High growth rates require permission to use the wallet. To solve this problem, this document introduces an integrated and responsible system for managing security certificates at the transport layer that represents the next generation of public key infrastructure.I merged two new architectures, introduced a new process, and created a registration and CA server. The domain owner has been notified. In supply chain management, the domain certificate signed by the CA is stored on the registration server, and the certificate server and the CA registration server are forwarded to the group that owns the domain. Compared with existing supply chain public key infrastructure products. The above-mentioned blockchain-based public key infrastructure scheme and registry are used for security and governance analysis.

Certificate Authority (CA) is a single point of failure in the design of Public Key Infrastructure (PKI). A single compromised CA breaks the entire infrastructure. The disclosed CA key can be used by adversaries to issue rogue certificates for any domains without the consent of the domain owners. These rogue certificates have been used in Man-in-the-Middle (MitM) attacks. Studies have been conducted to prevent and reduce the damages of breached CAs and rogue certificates in different ways. However, few have a mechanism to fully and efficiently verify whether a CA or a certificate can be trusted or not. There is a need to develop new methods to ensure certificates with a high level of trustworthy in order for the PKI to be more resistant to compromised CAs and rogue certificates.We propose an alternative approach to mitigate the issue of CA breaches by imposing multiple signatures on a server certificate. This is analogous with the redundancy approach that is commonly adopted in the practice of IT management. Since CAs are run and managed by independent organizations, the probability of breaking multiple CAs in a short period of time is reduced significantly. If S signatures are imposed on a certificate, the compromise of S-1 CAs will not break the PKI system. In this paper, we describe a framework of our approach and analyze its security. We also provide a brief overview of the most relevant counter measures against CA breaches and rogue certificates.

Blockchain technology is the cornerstone of digital trust and systems’ decentralization. The necessity of eliminating trust in computing systems has triggered researchers to investigate the applicability of Blockchain to decentralize the conventional security models. Specifically, researchers continuously aim at minimizing trust in the well-known Public Key Infrastructure (PKI) model which currently requires a trusted Certificate Authority (CA) to sign digital certificates. Recently, the Automated Certificate Management Environment (ACME) was standardized as a certificate issuance automation protocol. It minimizes the human interaction by enabling certificates to be automatically requested, verified, and installed on servers. ACME only solved the automation issue, but the trust concerns remain as a trusted CA is required. In this paper we propose decentralizing the ACME protocol by using the Blockchain technology to enhance the current trust issues of the existing PKI model and to eliminate the need for a trusted CA. The system was implemented and tested on Ethereum Blockchain, and the results showed that the system is feasible in terms of cost, speed, and applicability on a wide range of devices including Internet of Things (IoT) devices.

With the development of cloud services and the Internet of Things, the integration of heterogeneous systems is becoming increasingly complex. Identity management is important in the coordination of various systems, and public key infrastructure (PKI) is widely known as an identity management methods. In PKI, a certificate authority (CA) acts as a trust point to guarantee the identity of entities such as users, devices, and services. However, traditional CAs that delegate the operations to a specific organization are not always suitable for heterogeneous services, and a new methodology is required to enable multiple stakeholders to securely and cooperatively operate a CA. In this study, we introduce the concept of a consortium CA and propose a distributed public key certificate-issuing infrastructure that realizes a consortium CA. The proposed infrastructure enables multiple organizations to cooperatively operate a CA suitable for services involving multiple stakeholders. We identify four requirements for the cooperative operation of a consortium CA and design the proposed infrastructure with distributed ledger technology. Furthermore, we present the implementation of smart contracts with Hyperledger Fabric and prove that the proposed infrastructure satisfies the four requirements. Finally, we confirm that certificate issuance and verification are stable at approximately 4 and 3 ms, respectively.

ProofChain: An X.509-compatible blockchain-based PKI framework with decentralized trust

The public key infrastructure (PKI) provides security services for e-commerce, e-government and other cyber transactions. certification authority (CA), a critical component of PKI, acts as a trust third party (TTP) among these applications. A CA is usually controlled and operated by an authority in real world, which stores and publishes users' public key and other attributes. However, various types of attributes on certificates are always determined by several authorities instead of a single one. Based on the practical experiences, PKI must be built on real world trust relationships [1], but CAs, registration authorities (RAs) and other commodity PKI components cannotreflect these relationships among authorities well. Although some decentralized CA systems [2, 3] are designed and these CAs are operated by several administrators cooperatively, they focus on the security of CApsilas private key but not the trust relationships among administrators. To the best of our knowledge, no systematic work has been conducted to integrate several real world authorities into a CA, reflecting their trust relationships through system structure. We present a decentralized CA system, which is built and operated on real world trust relationships among several authorities, and issues standard X.509 certificates. Different authorities are responsible for different attributes on certificates, which make the certificates more trust and make the CA more similar to real world.