=Paper=
{{Paper
|id=Vol-2353/paper44
|storemode=property
|title=Collective Digital Signature Protocol on the Basis of EC-GDSA to Protect of the Doctors Concilium Medical Conclusion
|pdfUrl=https://ceur-ws.org/Vol-2353/paper43.pdf
|volume=Vol-2353
|authors=Hanna Nelasa
|dblpUrl=https://dblp.org/rec/conf/cmis/Nelasa19
}}
==Collective Digital Signature Protocol on the Basis of EC-GDSA to Protect of the Doctors Concilium Medical Conclusion==
https://ceur-ws.org/Vol-2353/paper43.pdf
Collective Based on EC-GDSA Digital Signature Protocol
to Protect the Doctors’ Medical Conclusion
of the Consilium
Hanna Nelasa1[0000-0002-3708-0089]
1
Zaporizhzhia National Technical University, Zhukovsky str., 64,Zaporizhzhia, 69063, Ukraine
nelasa@zntu.edu.ua
Abstract. Modification digital signature protocol EC-GDSA on elliptic curves
to collective form for telemedicine is proposed. This form may be used for se-
curity authentication of general conclusion of the doctors’ concilium. Computa-
tional algorithm is given.
Keywords: telemedicine, cryptography, collective digital signature protocol,
elliptic curve, EC-GDSA
1 Introduction
The fundamental task of each state is to ensure the right of its citizen to health and
safety. There is a high concentration of technical and human resources in large cities
and metropolitan areas in Ukraine. In such a situation, qualitative, timely and quali-
fied medical care is not available to the majority of the population living in rural ar-
eas, what leads to a deterioration of the health of the population and average life ex-
pectancy decrease. The main task of modern medicine is to raise the quality of life of
the population, increase the level of availability of medical services at the expense of
the latest medical technologies. Increasing demands of Ukrainian people regarding the
quality of medical goods and services compel the society look for new ways and
forms for its satisfaction, or at least to improve existing ones. One such way is tele-
medicine.
Telemedicine is a complex of actions, technologies and measures used during the
medical care using the means of remote communication for the exchange of informa-
tion in electronic form. Medical assistance with application of telemedicine involves
the opportunity of providing the patient with medical services for counseling, diagno-
sis, treatment using means of remote communication in the form of information ex-
change in electronic form, including by sending electronic messages, holding video-
conferences [1]. Telemedicine services have already been developed and popularized
abroad.
Telemedicine services are very comfortable and the most effective in remote areas.
On-line consultation with physicians is much cheaper than a trip to a doctor and al-
lows one to get a consulate faster. Implementation of telemedicine technologies will
also reduce the number of physical visits to the medical institution by patients, as well
as early discharge from the hospital and further undergo certain procedures and moni-
toring of a health status at home.
Conditionally, telemedicine can be divided into three general directions related to
medical education, the interaction “doctor-to-doctor” and the interaction “doctor-to-
patient”. An important aspect here is the issue of transmission, processing, analysis,
storage, protection of medical information and safe identification of the users of tele-
medicine services. So, telemedicine is a direction of medicine simultaneously com-
bines telecommunications, information technologies and medical education.
In order to provide telemedicine services, it is necessary to comply with the re-
quirements of the Law of Ukraine [2], the Order of the Ministry of Health of Ukraine
[3] and the requirements of the current legislation on information security.
Confidential medical information is transmitted through computers and open net-
works, and requires the protection and authentication.
The urgency of the issues of protection of telemedicine information and ensuring
the proper level of cryptographic security is undoubted. This is due to the fact that the
latest medical technologies and measures, including telemedicine counseling, are
being implemented and used in the practice of healthcare institutions. The provision
of telemedicine services should ensure the preservation of personal, medical and other
secrets provided by the legislation of Ukraine, as well as the confidentiality of per-
sonal data. Particularly, software used for telemedicine counseling should provide the
appropriate level of protection of information and its authenticity by using an elec-
tronic digital signature.
Mandatory services to be provided to clients and owners are services such as integ-
rity, integrity, authenticity, availability, confidentiality and reliability. The quality of
providing the specified services and the level of guarantees to a large extent is deter-
mined by the methods, mechanisms and protocols of cryptographic protection of in-
formation. In order to provide the specified services with the necessary level of guar-
antees, it is necessary to use asymmetric and symmetric cryptographic transforma-
tions as well as cryptographic authentication protocols and the establishment of keys
based on them.
Immediate implementation of medical information systems (telemedicine, elec-
tronic medical cards, "mobile medicine", cloud technologies, etc.) to the practice of
the physicians will lead to increase in the competitiveness of domestic health facilities
and their financial and economic security.
Directions of activity of large medical clinics and centers of private and state own-
ership concerning telemedicine are connected with “virtual clinics”, telemedicine
consultations, “another thought” service and a consultation of the physicians.
2 Formal problem statement
The following main types of telecommunications are used for the transmission of
medical data: stationary and mobile telephony; Internet (IP - protocol); GSM and
CDMA networks (SMS). Individual telemedicine is often used for mobile communi-
cation and wireless Internet (GPRS, CDMA, 3G, 4G). The protection of transmitted
medical information in home telemedicine systems is carried out with the help of
various software and hardware, primarily cryptographic, by encryption.
The development and convenient implementation of digital signature cryptographic
protocols based on elliptic curves can be a tool allows medical personnel transmit and
receive relevant messages and medical information with adequate cryptographic sta-
bility and the required speed when telemedicine tools are used.
Conсilium is a meeting of several doctors of one or different specialties. Conсilium
may be necessary to establish the state of health of the examinee, diagnosis, determi-
nation of medical forecast, tactics of further examination and treatment, expediency
referral to a specialized department or other, profile, medical institution.
The key difference between the doctors' congress is the collective responsibility for
the content of the medical conclusion. To ensure the authenticity of such a document
in the telemedicine system, authors are encouraged to use the collective digital signa-
ture protocols. In contrast to multiple signatures [4], where signing and checking of an
electronic document is important for the sequence of signatures / signatures of each
participant and, in addition, the size of the signature increases proportionally to the
number of participants.
For the time being in Ukraine, with the aim to ensure the functioning of telemedi-
cine networks, it is planned to use the specialized software, which corresponds to: the
DICOM standard. One of the advantages of the DICOM standard is the integration of
visual data with medical data in a single file, which is why the formation of a DICOM
file/package is crucial. A separate DICOM file includes, in addition to the title and
image (which may contain three-dimensional information) a set of graphic and text
data (relative to a patient).
The high speed of IT development forces government authorities to learn how to
use them to improve the efficiency of work and be prepared for rapid change. Ger-
many is one of the leading countries in the field of Internet development in applying
cryptographic primitives and protocols and is guided by the US and EU standardiza-
tion system. In this regard, it is important for Ukraine to study the German experience
and determine the possibilities for its application in terms of cryptographic protection
of information in general and in particular in the medical sphere.
The goal of the work is modifying the EC-GDSA electronic digital signature pro-
tocol into a collective form for the purpose of cooperation with clinics in Germany
and other countries to create telemedicine services for the physician consultation and
"second opinion" services, as well as its software implementation in the form of cli-
ent-server application.
3 Literature review
Theoretical and theoretical foundations concerning the functioning of telemedicine
systems, as well as information security in computer networks and systems, are con-
sidered in the works of domestic scientists, Godlevsky L.S. [5], Kovalenko O.S.[6],
Lyakh Yu.E. [7], Martsenyuk V.P. [8, 9], Mayorov O.Yu. [10], Minzer O.P. [11],
Khimzon I.I. [12]. Questions about the approaches to protecting data protection in
medical systems using cryptosystems, and increasing the reliability of cryptographic
keys are also considered by such foreign experts asYudin O.K. [13], Venkatasubra-
manian K.K.[14], Cherukuri S. [15] and many others.
There is a problem of collective responsibility for the contents of a document (in
this context, a medical conclusion) in telemedicine systems. From an IT point of
view, it can be solved with a multiple signature[4]. But in this case the order of sign-
ers and verificators is important. And the size of the signature increases proportionally
to the number of signers.
To eliminate these shortcomings, a new approach to the formation of a collective
public key based on users' public keys was proposed [16]. Based on this approach,
collective digital signature protocols are developed, including those based on modern
electronic digital signature standards in different countries [17-21]. These protocols
use a common (collective) public key, which is formed on the basis of the individual
public keys of the group of users. The practice of electronic digital signature systems
enables the use of standard open source directories and / or standard public key cer-
tificates (Internet accessibility), which facilitates the practical application of a new
approach to generating a collective electronic digital signature.
At this time, cryptography on elliptical curves[22-24], the principles of which were
independently proposed by N. Koblicz and V. Miller, have been widely used to offer
open-source cryptographic protection systems. In Ukraine, the research of electronic
digital signature on elliptical curves is also engaged in a large number of specialists,
including I.D. Gorbenko, M.M.Savchuk, G.Z. Khalimov V.I. Dolgov, V.K. Zadiraka,
O.O. Kuznetsov, A.V. Bessalov and others.
4 Threat analysis
Telemedicine systems, as well as other information and telecommunication systems
have problems with the security of information. This is tied to the fact that telemedi-
cine and telecommunication services are perceived separately from information secu-
rity services, but should be considered complexly.
To a greater extent teleconsultation is carried out between doctors, and much more
rare between a doctor and a patient. In the first case of telemedicine consultation, the
opportunity of mutual exchange of electronic messages with files of various formats
is very important (results of diagnostic examination, results of analyzes conducted,
etc.). In this case, the most practical in terms of efficiency and economic feasibility is
the sharing of files that are confidential, so the necessary protection measures should
be applied to this information. In telemedicine systems, which include local networks
(central subsystem with workstations, servers and data warehouses), to remotely in-
teract with its users, remote connections of the global network are used.
Separate clinical and informational security when providing telemedicine services.
Clinical security in telemedicine is related to telemedicine systems, to what extent
they affect and to the extent that they are safe for the life and health of people in-
volved in the provision of telemedicine services (patient, doctor, engineer, etc.). In-
formation security is about medical and personal secrets, it is the security of network
infrastructure, as well as information and telemedicine systems from interference
(intentional or accidental, internal or external), theft of medical or personal informa-
tion, blocking processes that impede the work of users.
Loss and falsification of medical data may occur as a result of the negative impact
of software, computer viruses, improper performance and equipment failure, negli-
gent or intentional user actions. The threat and disadvantage of access to telemedicine
systems are DoS attacks directed at intermediate and end nodes, as well as failures in
equipment, damage to communication channels, substitution of an authorized object,
listening of communication channels; loss of data (in full or in part), systematic falsi-
fication that is typical of most remote access systems.
Information security is provided through the use of the following telecommunica-
tion and hardware-software solutions: corporate medical networks, closed channels
(Virtual Private Network); cryptographic protection and electronic digital signature;
spam and antivirus protection; application of authorized access to servers, separate
databases, workstations, etc .; transmission of information in anonymous form; the
use of international standards (DICOM, SCP-ECG, etc.) in the transmission of infor-
mation.
Security policy should be formed depending on the particular situation and tasks,
in order to protect the personal data of a patient, it is proposed to use a variety of
cryptographic algorithms, to use electronic digital signature for the transmission of
medical information.
Regarding the ways of organizing telemedicine services within the hospital itself, it
is possible to carry out diagnostic manipulations (e.g., ECG) by middle medical per-
sonnel, and the reading of the diagrams and the diagnosis are performed by qualified
doctors in the functional diagnostic department. In case of the need for telemedicine
counseling involving simultaneously two or more doctors-consultants, a telemedicine
consultation (concilium) is carried out.
5 The modified method of digital signature based on EC-GDSA
In the event that a doctor encounters a complicated case in the process of treating
patients in his medical practice, he usually needs additional advice (advice) from an-
other specialist (the " another opinion" service) or several colleagues (a physician's
consultation) at his or her medical institution, or else, within the city, country or
abroad. In those cases where distance is a critical factor, remote counseling is pro-
vided through telemedicine.
Germany is one of the most developed states of the European Union with a high
level of development of the market of telemedicine services, which is potentially the
most ready to introduce new technologies.
Let's consider the national standard of electronic digital signature of Germany EC-
GDSA [table 1], and we modify it to a collective form for the purpose of organizing
the interaction of several doctors in consulting patients.
Let's illustrate the diagram of the deployment of the software complex
(Figure 1), which ensures the authenticity, confidentiality and integrity of the medical
conclusion when carrying out the consultation of physicians.
Table 1. - The EC-GDSA Digital Signature Standard
Formation of a digital signature Verification of digital signature
Input: secret key d , public key Input: public key Q , general system
Q d 1 P , general system parameters, digital signature r ', s ' for
parameters.
message M ' .
Output: digital signature r , s for Output: The signature is valid or not.
message M .
1. h H ( M ) mod n ; 1. h H (M ) mod n ;
2. Choose random k 1,..., n 1 ; 2. w (r ) 1 mod n ;
3. k P ( x, y ) ; 3. u1 h w mod n ;
4. r ( x, y) mod n ; 4. u 2 s w mod n ;
5. s ( kr h) d mod n . 5. ( x , y ) u1 P u 2 Q ;
6. v ( x, y ) ;
?
7. r' v
The system consists of:
- Server - leading doctor;
- Client - doctors - consultant from 1 to l .
Diagnostic equipment is directly connected to the host's doctor's server.
Consider the modification of the current EC-GDSA Digital Signature Standard for
the implementation of a collective signature, which may be useful for ensuring the
safe authentication of a general medical conclusion when the consultation is carrying
out.
The protocol consists of three parts: the generation of a public key, the formation
of a collective signature, the verification of the collective signature.
The designation:
P - the base point of the elliptic curve (the general parameter of the cryptosystem);
l - number of signatories (consultants);
n - the order of the cyclic subgroup of the elliptic curve points;
d i - the secret key of the i-th signer (doctor-consultant);
h – the hash of the document (medical conclusion);
Q - general public key (point of the elliptic curve);
Qi – share of the public key of the i-th doctor-consultant (EC point).
Doctor -
consultant (Client)
Leading doctor
(Server) Doctor - consultant
(Client)
Diagnostic
equipment Doctor -
consultant (Client)
Fig. 1. - Diagram of the deployment of a software for concilium
Part 1. Generation of a public open collective key.
1. The leading doctor (Server) initiates the calculation of the general public key
(point Q). After that, each doctor-consultant (Client) calculates the share of the public
key, which is then transferred to the leading doctor.
Qi d i1 P .
2. The leading doctor (Server) calculates the total secret key Q, as the sum of the
shares of the public keys of the group of l signers (consultants of the concilium).
l l
Q Qi d i1 P .
i 1 i 1
Part 2. Formation of a collective signature.
1. A leading physician (Server) calculates a hash of a document (medical conclu-
sion) and transmits it to all doctors-consultants (Client).
2. Each i-th subscriber (doctor - consultant, Client) calculates a point as follows:
a) selects a random parameter (random variable) k i , 1 k i n ;
b) calculates the point Ri k i P
c) sends it to the Server.
3. The leading doctor (Server) calculates the total point R as the sum of Ri :
l
R Ri ( X R , YR )
i 1
4. The leading doctor (Server) calculates the first part of the collective signature
r ( R ) X R mod n
and sends it to all signers.
5. Each subscriber (doctor-consultant, Client) calculates its part si :
si (k i r h)d i mod n
using its private key d i , and sends it to Server
6. The leading doctor (Server) calculates the second part of the collective signature
l
s si .
i 1
7. Collective signature is a pair of numbers – (r,s).
Part 3. Checking the collective signature.
1. The verifier calculates the hash of the document (medical conclusion).
2. The verifier calculates the values:
w (r ) 1 mod n ,
u1 h w mod n ,
u2 sw mod n .
3. and, using an open collective key Q , forms a point
( x , y ) u1 P u 2 Q
and calculates the value
v ( x, y) x mod n .
5. If r v , then the signature is authentic, in the other part it is
forgery.
Justification of the correctness of the submitted protocol.
l
Since the value of r is determined by the formula r ( R) (
k P) when form-
i 1
i
ing a signature, and when checking the signature verifier u1 P u 2 Q is the point R ,
then
l l
u1 P u2Q hwP swQ hwP sw d i1 P w(h s di1 ) P
i 1 i 1
l l l l
r (h [(ki r h)di ] d ) P r (h ki r h) P ki P R
1
i
1 1
i 1 i 1 i 1 i 1
as a result we have:
v (u1 P u 2 Q ) = (R ) ,
which corresponds to the value r when the signature is formed.
Note that the Server function can act as a separate individual of the protocol, and
one of the consultants. In this case, it combines Server and Client functions, which
does not interfere with the correct operation of the protocol. If the number of partici-
pants equals two, we have the implementation of the "another opinion" service, which
from the point of view of technical implementation is a special case of a concilium.
6 Conclusion
Thus, modern economic, scientific and social changes, rapid development and intro-
duction of innovative technologies, and a significant increase in data exchange infor-
mation processes require timely response to changes in the medical sphere, and oblige
comprehensive protection and confidentiality of medical data in modern telemedicine
systems.
The authors carried out an analysis of threats and modern methods of protecting
confidential medical information. The analysis of possible variants of confidentiality
and identification of the authorship of electronic communications for the provision of
telemedicine services, as well as analysis of critical, in terms of information security,
elements and communication channels infrastructure of telemedicine systems.
It is established that in the context of the reform of the health care of Ukraine, a
significant reduction of the bed fund, important issues are the improvement of medi-
cal diagnostic processes, the implementation of information and telecommunication
technologies, the organization of interaction between medical, preventive and special-
ized health care institutions through telemedicine , remote provision of qualified
medical services, maximum utilization of the intellectual potential of the best clinics.
In the case of the need for telemedicine counseling with the participation of several
consultants, a telemedicine consultation is conducted. It has been established that
some issues, including those concerning the practice of the use of a collective digital
signature in domestic health care institutions, for example, for the consultation of
physicians, remain unresolved. Germany is one of the most developed states of the
European Union with a high level of telemedicine market development, potentially
the most ready to introduce new technologies. Therefore, the possibility of modifying
the current EC-GDSA electronic digital signature standard for Germany for the im-
plementation of a collective signature is considered, which may be useful for ensuring
the safe authentication of a general medical conclusion when physician consultation is
carrying out.
The development of software for the proper level of cryptographic protection of in-
formation in telemedicine, the implementation of the EC-GDSA collective digital
signature protocol, including to solve the problem of conducting a consultation of
doctors, can also be used for cooperation with medical institutions in Germany and
other European countries and the world to create a telemedicine service "second
thought". For this purpose, the analysis and research of modern digital signature stan-
dards based on cryptographic transformations in the groups of points of elliptic curves
has been carried. The proposed collective digital signature protocol is based on the
EC-GDSA standard using a method similar to another one used in the collective sign-
ing protocol DSTU4145.
A software package with a client-server architecture is developed. It allows to en-
sure the preservation of the authenticity, integrity of the non-contradiction of elec-
tronic medical documents by protecting them with collective digital signature meth-
ods, based on the standards DSTU4145, EC-GDSA. To develop the project, the C ++
programming language and the Miracle cryptographic library were selected, which
includes the functions of long arithmetic and the implementation of the arithmetic of
elliptic curves defined over the simple and extended finite fields of Galois.
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