###### Abstract  
(1) Background: Third-generation sequencing (TGS) technique directly sequences single deoxyribonucleic acid (DNA) molecules, enabling real-time sequencing and reducing sequencing time from a few days to a few hours. Sequencing devices can be miniaturized and DNA-reading sensors placed on the body to monitor human health and vital signs, building an \"internet of living things\" (IoLT) facilitating ubiquitous healthcare services. In many cases, patients may wish to directly connect to each other for purposes of sharing real-time sequencing data, medical status or trading genomic data, etc. (2) Problems: User registration for a specific service may be limited due to some reason. Registering for multiple redundant services would also result in wasted money and possible wasteful communication overhead. In addition, since medical data and health information are very sensitive, security and privacy issues in the network are of paramount importance. (3) Methods: In this article, I propose a cross-server end-to-end (CS-E2E) patient authenticated key agreement protocol for DNA-based healthcare services in IoLT networks. My work allows two patients to mutually authenticate each other through assistance of respective servers, so that they can establish a reliable shared session key for securing E2E communications. The design employs multiple cost-saving solutions and robust cryptographic primitives, including smart-card-based single sign-on, elliptic curve cryptography, biohash function, etc. (4) Results: My proposed protocol is proven to be secure against various attacks and to incur reasonable communication cost compared to its predecessor works. The protocol also provides the support for more security properties and better functionalities. (5) Conclusions: The E2E communications between the patients are properly protected using the proposed approach. This assures a secure and efficient cross-server patient conversation for multiple purposes of healthcare communication.  
third-generation sequencing (TGS); DNA-reading sensor; onsite DNA sequencing; ubiquitous healthcare (U-healthcare); internet of living things (IoLT); smart-card-based single sign-on (SC-SSO); end-to-end (E2E) communication; key agreement; three-factor authentication  
T.-V.-C.-S.-.  
vital signs, building an \"internet of living things\" (IoLT) [3; 4]. Taking nanopore sequencing technologies as an example, SmidgION is a very small nanopore sequencer designed to be run on smartphones or mobile devices using their batteries and dedicated apps [3]. The DNA samples are loaded into the tiny sequencer from the sensors. The data produced include FAST5 (HDF5) files and/or FASTQ files [5]; they are either stored on the phone's memory or uploaded to the cloud. In this way, medical clinics can screen for new viruses in seconds, and researchers can obtain DNA sequences in real time for specific analysis. Ubiquitous healthcare (U-healthcare), which is a combination of electronic and mobile healthcare, is more concerned with person-centric therapy rather than traditional hospital healthcare [3]. To this end, DNA-based sequenced data are completely useful for U-healthcare, since it facilitates patient-centric service and personalized treatment process, for instance, real-time monitoring of body fluids [3].