SECURE ACCESS TO MEDICAL INFORMATION BY SMART CARDS
`
`R. BEUSCART (MD, PHD) (*), C. GRAVE (MD) (**), P. GEORGE(*)
`
`(*) RD2P (Recherche et Developpement Dossier Portable)
`Hopital CALMETTE - 59037 Lille Cooex
`
`**DIM - Rez-de-jardin - Hopital CALMETIE - Bd du Pr. LECLERCQ
`CHRU de Lille - 59037 Lille Cedex
`
`Summarv:
`
`The recent development of Medical Information
`Systems is due to the connection of medical data bases through
`networks.But this development emphasizes the problems of
`security and confidentiality of medical data
`This security requires the implementation of three
`complementary functions : identification-authentication,
`signature, encryption. The smart card is a possible tool for this
`security because of its micro-computer and RAM Memory. The
`most frequently used algorithm is TELEPASS. Recently,
`standard algorithms (RSA and DES) were implemented in
`enlarged memory cards. The Professional Access Card (CPS in
`France) and specific "Key Cards" are vectors for the
`generalization of security statements in the medical domain.
`
`Key words : Smart card , Security , Tele - Medicine ,
`Communication systems
`
`Introduction :
`
`The management of medical information is more and
`more realized through computer systems. Hospitals are
`dev~loping Hospital Infonnation Systems for the archieving of
`mechcal records and for the communication between medical
`units, labs, X-Ray departments, administrative boards. The
`development of telematics and public networks (LAN or WAN)
`makes possible the transmission of medical information and the
`synchronous as well as asynchronous exchanges between
`physicians.
`But these new technologies arise general problems
`concerning the confidentiality and the security of the transfer of
`medical data.
`
`I. LEGAL AND ETHICAL CONSTRAINTS.
`
`The rules concerning the security of the transmission
`of medical data between medical units and physicians are widely
`different from one country to another. In France, the
`Commission Nationale Infonnatique et Libertes (CNIL) pointed
`out at the following points :
`1) It is recommended to use and to send a record number and not
`the patient's name. If necessary identity items must be
`encrypted.
`
`2) For sensitive applications in the medical domain (Psychiatry,
`AIDS, Blood-diseases) it is recommended to use identifications
`and authentication by smart card (micro-processeur card).
`3) If the.results of blood analysis are send through the network ,
`automatic correction of errors must be possible.
`
`These recommendations are necessary both to protect
`~he medical information of the patient and to guarantee the
`mdepedance of the physician towards health care institutes and
`insurance companies.
`The electronic signature is also possible by means of
`smart card but legal constraints are limiting this use. In fact,
`only the manual signature is recognized as legally valid.
`In summary. there are 3 constraints for a wide use of
`telematic networks in the health care domain :
`- Identification, authentication,
`- Security of the transfer of data..
`- To avoid the fraudulent use of medical information ..
`
`II. PROFESSIONAL ACCESS CARD.
`
`II. I Micro-processor cards.
`
`A smart card (or micro-processor card) is made of:
`- A micro-processor;
`- Three memories.
`. RAM memory for temporary storages of information
`.
`durmg the calculations and the operations of the micro(cid:173)
`processor.
`. PROM memory for fixed programs written when the
`card is manufactured.
`. A programm~ble memory [EPROM or EEPROM].
`~mpty "":'hen the card 1s manufactured, containing the new
`mfonnauon necessary for the users of the card. The capacity of
`this memory is variable from 1024 bytes to 64 kbytes. This
`part of the memory is divided in a number of zones the access of
`which may be :
`- Free.
`- Confidential (they~ protected by a secret code),
`• Secret (only the micro-processor of the card can have
`access to this information).
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`The chip is fixed under a metallic patch and the link is
`effective by means of six contact points for asynchronous
`exchanges.
`
`11.3 The professsional Access Card.
`
`In the first experiences of Patient Data Cards in
`Europe, the access to sensitive infonnation was protected by the
`use of a "key" card, distributed to the professionals who would
`take the patient in charge : physician, nurse, chemist,
`physiotherapist. .. But the rights for reading/writing were
`different according to the profession of the owner. A physician
`could read and write all the areas of the patient data card whereas
`the nurse could only read emergency and historic infonnation.
`The French Ministry of Health has decided to generalize
`the use of the smart card as a professional access card for :
`- The identification and authentication of the owner,
`- Securtity of data,
`- Coherence of the cards systems.
`
`Ill. SECURITY FUNCTIONS
`
`The security functions are assured by the micro(cid:173)
`processor smart card using specific algorithm
`for
`indentifications of the owner but also to secure data transfers
`between medical units.
`
`III. I. The TELEPASS example.
`
`One of the most common algorithm is TELEP ASS
`which has the following fwictionalities :
`- The algorithm corresponds to a program or a function
`F, stored in the micro-processor with secrete data S written in
`the card and confidential data In wriuen by the responsible of the
`specific application. We can take 2 examples of the use of the
`"TELEPASS" smart card:
`
`1) Authentication
`If n persons are authorized to access to the application
`"X", each person has a card with :
`- Program F and a personal code
`- A secret number S
`- The identity In of the bearer.
`When the card is introduced in a reader, then the system
`reads the identity In of the bearer and sends to the card a random
`number R. Then the micro-processor of the card computes :
`
`The decryption function of C is :
`P= dK(C)
`So a smart card is, with a simple algorithm, a very
`secure method for identification, authentication, encryption or
`decryption of confidential data as medical information.
`
`III.2. RSA and DES.
`
`Recently, smart cards with higher RAM memory size,
`permitted the implementation of higher level algorithms.
`
`. The RSA (Rivest, Shamir, Adleman) algorithm uses
`the following function : When X wants to send the m message
`to the user A, them it computes : (mP mod n) and sends this
`result to A. Only the user A may rebuild m using the secret
`exposant s to calculate :
`m = ( mP modn)S mod n
`
`This RSA algorithm exists on specific smart card as
`MIMOSA (Gemplus)
`
`. The DES algorithm was obtained by arrangement of
`several encryption functions. DES is the "Data Encryption
`Standard" published as a Federal Information Processing
`Standard n°46 in 1977. In the DES algorithm, encryption and
`decryption use an algorithm on data blocks of 64 bits, under the
`control of a 56 bits key. A block is submitted to an initial
`permutation, then to a complex calculation (depending on the
`key) an then to an inverse permutation.
`
`IV. CONCLUSION
`
`Smart cards, because they are equiped with three types
`of memory and a true micro-computer, are effective and secure
`ways to ensure the confidentiality of medical data. The principal
`possible functions are :
`- Identification
`- Authentication of the bearer by means of a secret code
`- Electronic signature
`- Encryption and decryption of electronic mails.
`
`The recent availability of classical algorithms as DES
`or RSA on the smart card reinforces the potential of smart cards
`as a key acces to medical information.
`
`A= F (S, In, R)
`
`REFERENCES :
`
`and sends this result to the system which has the list of
`the n authorized clients. Then the system computes
`A'=F(S, In, R) and verifies the equality : A=A'. The key 'R' is
`secure as the random number R is generated every time ; if K
`and R are 64 bits long, then the risk of rutilizing the same key
`is 10-9.
`
`2) Encryption.
`The system sends C and the random number R. At
`reception, the calculation is the following one :
`K = F(S, In, R).
`
`R. BEUSCART and P.C. PARADINAS
`Smart cards for Health Care
`In "Telematics in Medicine" J. Duisterhout ed.
`p. 357-367. - North-Holland, 1991.
`
`J.M. LAMERE, Y. LEROUX, J. TOURLY
`La securite des reseaux - p. 294-300
`Dunod ed. Paris (1987)
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