Page 79 - 2023-Vol19-Issue2

75 |
• Step4. Upon receiving the information in Step 3, CHSk
computes CHU' i = H(CertUi ? VCUi ) and compare be-
tween CHUi =? CHU' i . If so, CHSk accepts the user’s
login request and allows him to use the resources and
services of system based on his privileges. Then, CHSk
computes SKUi = SKUi ? VCUi and decrypts CertU' i =
DecSKU''i (ECertUi ) . Otherwise, he rejects the current
phase.
Note: Now the user can work according to the his privi-
leges granted to him from administor (doctor, administrator).
C. EHR Migration Phase
In this phase, the patient wishes to receive medical treatment
in a certain institution CHSK' , which does not necessarily be
the same institution that registered her/him previously.
• Step1. Wi computes a random value rWi with a random
number ri ? Zn*, where rWi = ri ? HWi . After correctly
calculating the foregoing, he sends his request to the
CHSk in an anomaly and freshness message style. The
ims ecsosmagpeutreedqfureosmt i(nIcDlu'AWdei s=(CIDerAWtWii?, IrDW'AWi)i
, EAWi ), which
and encrypted
main parameter via his shared key EAWi = EncSKWi (rWi).
Wi CertWi-,D?A' Wi ,EAWi CHSk
• Step2. Following the receipt of this message by CHSk,
it can check the CertWi with his index file; if it is found
then go to step 3. Otherwise, go to the Step4.
• Step3. Wi performs the main medical treatment in his
institution, the results report (RRWi ) should be added
to the EHRWi by EHRUj directly and apply the same
functions in the upgrading phase.
• Step4. This case means that the patient wishes to do
some medical treatments outside of his healthcare cen-
ter. The new institution CHSK' is used public key of
HCA to encrypt AEpk1 = AEncPUHCA ((CertWi , ID'AWi ,
EAWi )), and sends (IDCHSK' , AEpk1) to HCA for ensur-
ing from the validity of the patient and his institution.
• Step5. This message tuple IDCHSK' , AEpk1 is delivered
to HCA. When HCA has received this message with
IDCHSK' , it can decrypt AEpk1 based on PrHCA in or-
der to restore all parameters using ADecPrHCA(AEpk1).
First, it can fetch the random value rWi' = DecSKWi (EAWi ),
we notice this step also verifies certificate of Wi relied
on his shared key SKWi and CertWi . Second, it compares
between ID'AWi and IDAWi ? rWi', if they are matched,
it ensures from the authority of Wi and saves current
parameters for usage in the next steps. Finally, HCA
Hamed & Yassin
returns the result R to the server CHSK' using the fol-
lowing function.
R= (H (rWi' CertWi )) if Wi is registered
(H (rWi' 0)) if Wi isnot registered
As a result, HCA detects Wi’s institution CHSk based
on his certificate CertWi . It sends (R, IDCHSk ) to CHSK' .
• Step6. CHSK' receives this message challenge, it can
verify the patient by comparing HrWi ?CertWi with R.
When the above parameters are not valid, CHSK' notifies
the patient to register at a public healthcare center or
checks his authority with his medical institution CHSk
(see Fig. 4).
D. Treatment and Exchanging Phase
In this phase, Wi can do many medical treatments such as
tests of blood diseases, blood pressure, diabetes, Covid-19
infection, CT-Scan, MRI in the CHSK' .
(a) The results report (RRWi ) should be added to the EHRWi
existing in the original patient’s institution CHSk where
he belongs in the registration phase. Therefore, CHSK'
computes AEpk2 = AEncPUCHSk (CertWi , RRWi ) based on
the identification of patient’s institution detected previ-
ously in Step3.2. Finally, CHSK' sends message tuple
(IDCHSK' , IDCHSk , AEpk2) to HCA.
(b) The server HCA will behave according to the delegated
message tuple (IDCHSK' , IDCHSk , AEpk2) , and will ex-
change secure data of medical institutions (CHSk,CHSK' )
by forwarding patient’s data (IDHCA, AEpk2) to CHSk.
E. Upgrading Phase
When CHSk receives (IDHCA, AEpk2), it decrypts AEpk2
with PrCHSk . If it is valid, it can obtain RRWi , CertWi and
upgrade the information of EHRWi by adding the new status
of the patient Wi relied on RRWi . The upgrade process will be
performed by EHR user (EHRUj ) working as an employee
who has privileges that allow him to upgrade to the EHRWi .
Additionally, these privileges gained by the Administrator
(ADM), represent the role of Uj. Now, the EHRWi contains
the last update of the patient’s case. In an emergency patient’s
case, EHRUj can tell the family member about the patient’s
case by sending SMS-Emergency to the patient’s family mem-
ber (see Fig. 5).
IV. SECURITY ANALYSIS
This section evaluates security analysis of the proposed scheme
in terms of formal and informal security analysis as the fol-
lows: