Privacy preserving health data processing

The combination of secure multi-party computations (SMC) algorithms, encryption, public key infrastructure (PKI), certificates, and a certificate authority (CA) is used to implement an infrastructure and a toolset for statistical analysis of electronic medical record (EMR) data. EMR data are typically located at different general practices and hospitals. These general practices and hospitals are considered nodes in a computing graph. The infrastructure and toolset has to take into consideration legal, security and privacy issues involved in statistical analysis of such data. The described approach tries to support a wide range of possible SMC algorithms and computing graphs.

The Web public-key infrastructure (PKI) provides a mechanism to identify websites to end users for the purposes of encrypted communication. The security of the Web PKI primarily relies on certification authorities (CAs), trusted parties whose misbehavior can enable man-in-the-middle (MITM) attacks: the impersonation of websites to users, followed by the theft or modification of sensitive information. While many methods of addressing CA misbehavior have been proposed, no solution has been both effective and practical: able to protect websites users against C misbehavior and to be easily deployed and used by all parties involved. Thus, despite more than two decades of research advances, the Web PKI remains largely vulnerable to misbehaving CAs.In this thesis, I argue that we can use minimal changes to existing technology to build deployable solutions thatreduce the rate of successful MITM attacks in the Web PKI. Specifically, I present three projects that exemplifyeffective and practical approaches to improving the Web PKI. In IKP, I use the Ethereum cryptocurrency and smartcontract platform to build an insurance-like mechanism that disincentivizes CA misbehavior. In CAPS, I use twoglobal monitoring and logging systems, CT and Censys, to build a system that strengthens the existing PKI againstmisbehaving CAs and enables the secure incremental deployment of new and improved PKIs for theWeb. In SAINT, I use the SCION future Internet architecture to propose a PKI that unifies public-key authentication for naming, routing, and end-entity public keys in a federated environment, and identify challenges and desired properties in such an environment. Through this work, I provide a first step towards making a more resilient Web PKI a reality.

In public-key encryption, the secrecy of the public key is not required, but the authenticity of the public key is necessary to guarantee its integrity and to avoid spoofing and playback attacks. A user’s public key can be authenticated (signed) by a certificate authority that verifies that a public key belongs to a specific user. In this chapter, digital certificates, which are used to validate public keys, and certificate authorities are discussed. When public-key is used, it is necessary to have a comprehensive system that provides public key encryption and digital signature services to ensure confidentiality, access control, data integrity, authentication, and non-repudiation. That system, public-key infrastructure or PKI, is also discussed in this chapter.

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.

Traditionally, a Certification Authority (CA) is required to sign, manage, verify and revoke public key certificates. Multiple CAs together form the CA-based Public Key Infrastructure (PKI). The use of a PKI forces one to place trust in the CAs, which have proven to be a single point-of-failure on multiple occasions. Blockchain has emerged as a transformational technology that replaces centralized trusted third parties with a decentralized, publicly verifiable, peer-to-peer data store which maintains data integrity among nodes through various consensus protocols. In this paper, we deploy three blockchain-based alternatives to the CA-based PKI for supporting IoT devices, based on Emercoin Name Value Service (NVS), smart contracts by Ethereum blockchain, and Ethereum Light Sync client. We compare these approaches with CA-based PKI and show that they are much more efficient in terms of computational and storage requirements in addition to providing a more robust and scalable PKI.

An important and common prerequisite of many asymmetric cryptography systems is the availability of a secure mechanism for exchanging or distributing public keys. In this paper we compare two adaptive trust-based distributed schemes to deliver public keys in a peer-to-peer network. In such a scenario, centralized solutions, for example based on a certification authority or a public key infrastructure, cannot be used. For this reason we considered a completely distributed approach creating a sort of context aware web-of-trust. This is achieved in two different trust-based manners: one considering a classic request-response scheme and another one that exploits a Distributed Hash Table (DHT). We compare performances of both solutions trying to find an optimum trade-off.

Recent research works examine the potential employment of public-key cryptography schemes in e-health environments. In such systems, where a Public Key Infrastructure (PKI) is established beforehand, Attribute Certificates (ACs) and public key enabled protocols like TLS, can provide the appropriate mechanisms to effectively support authentication, authorization and confidentiality services. In other words, mutual trust and secure communications between all the stakeholders, namely physicians, patients and e-health service providers, can be successfully established and maintained. Furthermore, as the recently introduced mobile devices with access to computer-based patient record systems are expanding, the need of physicians and nurses to interact increasingly with such systems arises. Considering public key infrastructure requirements for mobile online health networks, this paper discusses the potential use of Attribute Certificates (ACs) in an anticipated trust model. Typical trust interactions among doctors, patients and e-health providers are presented, indicating that resourceful security mechanisms and trust control can be obtained and implemented. The application of attribute certificates to support medical mobile service provision along with the utilization of the de-facto TLS protocol to offer competent confidentiality and authorization services is also presented and evaluated through experimentation, using both the 802.11 WLAN and General Packet Radio Service (GPRS) networks.

CA (Certificate Authority) acts as the trusted third party, which serves to issue digital certificates and validate them in PKI (Public Key Infrastructure). Hence it's significant to ensure the CA system's security. The ECC (Elliptic Curve Cryptography) has the advantages of shorter key and higher efficiency, comparing with other public key cryptographies such as RSA. The purpose of this work is to design and implement a CA based on ECC by using Java programming technique, which can sign X.509v3 digital certificate to client and then validate client certificate. In application, the key pair (including public key and private key) can be got from the PKCS#12 (Public Key Cryptography Standard), which is used in encryption, decryption and digital signature. The ECC-based CA is used in the system of DRM (Digital Rights Management) to contribute to confidentiality, authenticity, integrality and non-repudiation in communication.

Certificateless public key cryptography (CL-PKC) can solve the problems of certificate management in a public key infrastructure (PKI) and of key escrows in identity-based public key cryptography (ID-PKC). In CL-PKC, the key generation center (KGC) does not know the private keys of all users, and their public keys need not be certificated by certification authority (CA). At present, however, most certificateless encryption schemes are based on large integer factorization and discrete logarithms that are not secure in a quantum environment and the computation complexity is high. To solve these problems, we propose a new certificate-less encryption scheme based on lattices, more precisely, using the hardness of the learning with errors (LWE) problem. Compared with schemes based on large integer factorization and discrete logarithms, the most operations are matrixvector multiplication and inner products in our scheme, our approach has lower computation complexity. Our scheme can be proven to be indistinguishability chosen ciphertext attacks (IND-CPA) secure in the random oracle model.

Public Key Infrastructures (PKI) are important for the security of many networked systems. The current designs of PKIs often rely on a centralized key Certification Authority (CA) for the certification and distribution of keys. This centralized entity poses a performance and scalability bottleneck. In addition, it creates a serious security risk – if the CA is penetrated, the security of the entire system is irretrievably compromised. In this paper, we present an innovative method to generate globally unique keys in a completely distributed fashion. The ability to perform distributed key generation facilitates decentralized PKIs. We present security analysis of the method as well as a set of experimental performance results. Our method scales well, and is cryptographically strong.

We consider a problem which was stated in a request for comments made by NIST in the FIPS97 document. The question is the following: Can we have a digital signature public key infrastructure where the public (signature verification) keys cannot be abused for performing encryption? This may be applicable in the context of, say, exportable/escrow cryptography. The basic dilemma is that on the one hand, (1) to avoid framing by potentially misbehaving authorities we do not want them to ever learn the “signing keys” (e.g., Japan at some point declared a policy where signature keys may be required to be escrowed), and on the other hand (2) if we allow separate inaccessible public signature verification keys, these keys (based on trapdoor functions) can be used as “shadow public-keys,” and hence can be used to encrypt data in an unrecoverable manner. Any solution within the “trapdoor function” paradigm of Diffie and Hellman does not seem to lead to a solution which will simultaneously satisfy (1) and (2).The cryptographic community so far has paid very limited attention to the problem. In this work, we present the basic issues and suggest a possible methodology and the first scheme that may be used to solve much of the problem. Our solution takes the following steps: (1) it develops the notion of a nested trapdoor which our methodology is based on, (2) we implement this notion based on a novel composite “double-decker” exponentiation technique which embeds the RSA problem within it (the technique may be of independent interest), (3) we analyze carefully what can be and what cannot be achieved regarding the open problem by NIST (our analysis is balanced and points out possibilities as well as impossibilities), and (4) we give a secure signature scheme within a public key infrastructure, wherein the published public key can be used for signature verification only (if it is used for encryptions, then the authorities can decrypt the data). The security of our scheme is based on RSA. We then argue how the scheme’s key cannot be abused (statically) based on an additional assumption. We also show that further leakages and subliminal leakages when the scheme is in (dynamic) use are not added substantially beyond what is always possible by a simple adversary; we call this notion competitive leakage. We also demonstrate such simple leaking adversary.We hope that our initial work will stimulate further thoughts on the non-trivial issue of signature-only signatures.KeywordsSignature SchemeRandom OracleRandom Oracle ModelCovert ChannelDigital Signature SchemeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Non-PKI methods for public key distribution

Certificate Authorities (CAs) are important components for digital certificate issuances in Public Key Infrastructure(PKI). However, current CAs have some intrinsic weaknesses due to the CA-centric implementation. And when browser and operating system vendors contain a CA in the software, they place complete trust in the CA. In this paper, we utilize natural characteristics of tamper-proof and transparency of smart contracts in blockchain platforms to design an independent entity, named the CA proxy, to manage life cycle of digital certificates. This management will achieve the certificate transparency. We propose a new system architecture easy to integrate the CA proxy with current CAs through applying the blockchain oracle service. In this architecture, the CA proxy, CAs, and even professional identity verification parties can accomplish life cycle management of certificates, signature of certificates, identity verification for certificates correspondingly. The achievement of the certificate transparency through life cycle management of digital certificates in blockchain platforms, when compared with traditional CAs, solves traditional CAs' trust model weaknesses and improve the security.

The certificate authority (CA) is the central trust point in a public key infrastructure (PKI). Great care should be taken by users when they make a decision to trust a CA. Unfortunately, the average user will rely on the software to provide an appropriate security warning when something has gone wrong and therefore may not give much thought to the decision when performing such a security operation. The updating of a CA certificate is an issue that needs to be accomplished in a secure manner with little or no intervention by a user. Techniques are now in use that can allow for update of a CA's certificate. The Secure Electronic Transaction's (SET) root certificate update method is just one example, but in a specialized case. This paper discusses a practical solution that potentially any CA could use to provide a secure in-band update of a CA's X.509 v3 certificate into a user's personal security environment (PSE). A method is also discussed that Java programmers can use for update of self-signed X.509 v1 personal certificates in Java keystores as well.

Secure end-to-end information exchange is a constant challenge in electronic communications. Novel security architectures and approaches are proposed constantly, to be followed by announcements of sophisticated attack methods that compromise them, while people suspect others, even more sophisticated attack methods never see the daylight. In the present work we propose a novel method for secure end-to-end communication based on biometric evidence to ensure security and integrity of the information exchanged. The traditional approach for securing the communication between two peers is through the use of secret key encryption combined with a public key approach for exchanging the common secret key to be used by the end peers. The public key part of the communication is based on a trusted authority for providing the public keys, a service provided through a Public Key Infrastructure (PKI). Public key infrastructures are vulnerable to man in the middle attacks, among other approaches that compromise their integrity. There has been a lot of work for providing robust PKI infrastructures, the proposed solutions are fairly demanding on network resources, hence public key solutions are not the security approach of choice in several applications that require light weight solutions. Here we propose an approach for providing secure end-to-end communications in environments where it is possible to have biometric based authentication, exploiting the nature of the application; voice communication being the typical example that we use as our paradigm for describing the method. During the establishment of the communication session, the end-peers exchange a challenge/signature token, the integrity of which is confirmed vocally when the voice communication initiates. The security of the method relies on the inability to mechanically impersonate an individual both because of the biometric user specific attributes of the human voice and video as well as the user customized profile of the exchanged information. The method is appropriate for ensuring the security of an encrypted phone conversation, guaranteeing the integrity of the session key exchanged in the beginning of the conversation. It requires minimal resources from the user handsets and no additional support from the network, so it is inherently scalable and readily deployable as it only needs an appropriately enhanced secure handset. ©2006 IEEE.