Electronic Health Records (EHR)

An Electronic Medical Record (EMR) is an electronic record of a patient’s medical care and is a digital version of paper documents and records in doctors and clinics. EMRs store data locally at the healthcare facility, whereas EHR aim to share health information among healthcare providers [17]. EHRs are more advanced regarding data sharing among healthcare providers, whereas EMRs include a partial patient history.

Note that, in this paper, the family doctor shares the patient’s medical data with the emergency doctor using blockchain. As it involves information sharing among medical institutions, the patient’s medical information is described using EHR notation.

Blockchain

Blockchains are categorized as Public (Permissionless) or Permissioned based on transaction transparency and administrator presence.

Bitcoin [22] epitomizes public blockchains, allowing participation without permission and lacking an administrator. On the other hand, permissioned blockchains, come in two forms: private and consortium. Private blockchains have single administrators and limited user access, while consortium blockchains involve multiple administrators.

Garay  et al. [16] analyzed the backbone protocol of the Proof of Work-type blockchain. In [16], the analysis was based on the honest majority assumption that most users are honest. They defined typical execution where the results of honest and malicious miners do not deviate significantly from the central expectation. With sufficiently long runs, the probability of non-typical execution occurring can be considered negligibly small. Under the honest majority assumption and from typical execution, k can be regarded as a security parameter, and the larger k is taken, the more we can assume that the honest miners are in agreement on the same chain. In this paper, we adopt the honest majority assumption in the blockchain network and assume that the protocol is executed on a single chain where the consensus is ensured among the honest majority.

Smart Contract

Smart contracts are a feature implemented in Ethereum, which has the next highest market value after Bitcoin and are automated programs that utilize blockchain technology to execute when conditions are met automatically. Stored on a reliable and tamper-proof blockchain, it increases the transparency of transactions and agreements and enhances trust without needing an intermediary.

Smart contracts are also part of decentralized applications and have a wide range of applications, including cryptographic assets, real estate transactions, and supply chain management. Smart contracts are typically used to automate contract execution so that all participants can see the results instantly without the involvement of intermediaries or loss of time.

Gas price refers to the cost of computational resources required to execute transactions and smart contracts on the Ethereum network. These costs are paid in the form of gas fees, which are determined by the amount of gas used to execute a specific process multiplied by the cost per unit of gas. Irrespective of the success or failure of the transaction, the gas fee must be paid in ETH, the native currency of Ethereum. The gas price is generally quoted in gwei, which is one of the units of ETH. One gwei is equivalent to one billionth of an ETH. For instance, a gas bill of 0.00000001 ETH can be represented as 10.0 gwei.

Testnet

Testnet is a blockchain environment that is not intended for production purposes. It is used to identify and fix bugs, code vulnerabilities, and other network issues that may impact the functionality of a blockchain project. To test smart contract functionality before deploying it on the production environment Mainnet, developers use testnets such as Rinkeby, Goerli, Sapolia, Polyscan, and Kiln. It is important to note that cryptocurrency on Mainnet has real value on the blockchain network and can be used to pay for transactions, but coins on testnet cannot be used on Mainnet. Transactions on Mainnet require real cryptocurrency, while transactions on testnet are free.

InterPlanetary File System (IPFS)

The InterPlanetary File System (IPFS) [5] is a hypermedia protocol created by Juan Benet in 2015. It uses P2P networks developed by Protocol Labs. Unlike HTTP, the primary protocol used on the Internet, which is “location-oriented,” IPFS allows users to access content using a content ID (CID), which is the hash value of the content. This means that instead of specifying a URL of the web server providing the content, users can view the desired content by using its unique content ID.

Tamper-Proof Hardware with Biometric Authentication Capabilities

Tamper-proof hardware refers to hardware devices and components that are highly resistant to external attack and physical manipulation, and are used to protect sensitive information and security-related tasks. Examples of tamper-proof hardware include Intel’s Software Guard Extensions (SGX) [4], as well as SIM cards and IC cards such as credit cards, which are widely used in the real world. Tamper-proof technology is also widely used in smartphones. It is implemented in the iPhone as “Secure Enclave [8]” and in Android devices as “Trusty TEE [10]”.

In general, tamper-proof hardware has the de facto standard “attested execution” functionality [24]. Algorithm 1 illustrates the “attested execution” function, where a digital signature key pair is used to ensure the integrity of executed programs within the hardware.

Algorithm 1

AESP’s brief algorithm.

First, the hardware manufacturer generates a digital signature key pair \((pk_D,sk_D)\). The output of any program executed in the hardware is signed with \(sk_D\). Next, the manufacturer installs an arbitrary program \(\textsf\) to run in the hardware. Finally, the program is executed. The program receives \(\texttt\) and outputs \(\texttt\). The \(\texttt\) is signed with the digital signature key \(sk_D\), and the signature \(\sigma _\texttt\) is generated. The signature \(\sigma _\textsf\) allows us to verify that the output \(\texttt\) was successfully computed and generated from the tamper-proof device and \(\texttt\) has not been tampered with.

We assume that our design of the pendant includes a SIM card, which is a portable hardware component, and that it communicates with the emergency doctor using Bluetooth, a short-range wireless communication standard for digital devices. For biometric authentication, we assume the use of methods such as fingerprint recognition, which is already widely used in smartphones and other devices. This method can be implemented on lightweight hardware with limited computing power [28] and can be used even if the patient is unconscious.

Diffie-Hellman (DH) Key Exchange protocol

DH public-key cryptography is a cryptographic protocol in which two parties each output a public key, from which a shared secret key is created only between them. Consider the case where Alice and Bob output their public keys to each other to create the shared secret key.

1.

Alice input \(1^\lambda \) to a probabilistic polynomial time algorithm \(\mathcal \) and then obtains a cyclic group \(\mathbb \) of order q.

$$\begin (\mathbb , g, q) \leftarrow \mathcal (1^\lambda ) \end$$

(1)

where \(\lambda \) is a security parameter.

2.

Alice chooses \(x \in \mathbb _q\) uniformly random and computes her public key as follows:

$$\begin pk_A = g^. \end$$

(2)

Then, Alice sends \(\left( (\mathbb , g, q), pk_A \right) \) to Bob.

3.

Bob chooses \(y \in \mathbb _q\) uniformly random and computes his public key as follows:

$$\begin pk_B = g^. \end$$

(3)

4.

Alice and Bob calculate the shared secret key, respectively.

$$\begin sk_ = (g^x)^y = (g^y)^x = g^. \end} \end$$

(4)