Journal of Internet Banking and Commerce ISSN: 1204-5357
ISSN: 1204-5357
+44-175-271-2024SATTAR J ABOUD
Department of Computer Science and Technology, Bedfordshire University, UK
MOUSTAFA AL-FAYOUMI
Department of Computer Science, Princess Summaya University for Technology, Jordan
MOHAMMAD AL-FAYOUMI
Department of Computer Science, Al-Isra University, Amman, Jordan
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In this scheme, we compute the fare that the passengers should pay based on the time of service for entry and exit of the scheme. The information and communication technologies let the use of e-tickets, which assists to decrease charges and enhance the control of the communications. But, these schemes should be secure anti-fraud and they should also protect passengers’ privacy. Thus, we have considered the security specifications for the time-typed schemes and we have introduced the scheme for every of the e-tickets fare schemes. The schemes propose robust privacy for good passengers. It means that, the service issuer does not capable to reveal the information of its passenger and, also dissimilar trips of the same passenger are not linkable. Also, anonymity for passenger can be revoked when they behave badly. The scheme has been applied and its result has been gauged. The outcome observes that scheme is appropriate to be employed in e-tickets fare scheme while they provide the better result with the high-quality mobile phone.
Privacy; Mobile Applications; E-Commerce; Applied Cryptography
The integration of information and communication technologies in e-ticket fare schemes lets to decrease costs and enhances the control of the communications; some cases can be the real-time traffic density monitoring and the administration strategy of communications based on the passenger flows. E-ticket fare schemes are designed for huge-density public transport rather than setting the passenger destination, the charge can be considered in time-typed scheme. The advantages of using this scheme involve the removal of selling and cash machinery, passenger ease, quicker travel and decreased the office expense. But, to accomplish this, an efficient e-ticket fare scheme becomes an essential. Therefore, the secure administration of passenger check-in and check-out of a scheme is required, as they pay consistent with this use. When the scheme identifies the passenger, recognizing their entry and exit points. It means that where they travel and if a scheme can trace their travels. Using such movements it can generate passenger profiles. This is the considerable confidentiality threat. It means that, it breaches the passenger privacy. Therefore, such e-ticket fare scheme has to protect the passenger confidentiality to stop profiling and tracking. However, if the scheme provides non-revocable confidentiality, some illegal, for example terrorists can provide the transport scheme to flee from the security services. Therefore, we have two different characteristics. To satisfy both characteristics, the scheme can revoke anonymity of the fixed passenger by means of the court order. The additional concern is the high number of passenger in the e-ticket fare scheme, needing then the scheme to be very quick in both entry and exit operations. The work provides the secure administration for e-ticket fare scheme, with robust confidentiality for sincere passenger. But, when the passenger acts corruptly, the identity can be revealed to pick authorized events, as the scheme provides revocable anonymity. Also, passenger does not require getting the new credential each time that they join the e-ticket fare scheme. This characteristic enhanced the scheme usability, since in the preceding e-ticket fare scheme new credential detail is required for each new trip.
In this paper, we consider the e-ticket fare scheme regarding the revocable anonymity of passenger. In such scheme, the issuer can connect dissimilar trips from the same passenger. In the linkable scheme, the revelation of an identity of the passenger in the trip produces the revelation of all the trips of the same passenger, vulnerable anonymity. Thus, the issuer knows where they travel, what time of the trips. The facts of passenger actions let the construction of passenger profiles. Such profiles are practical for the issuer since they are used generally to enhance the transport scheme or more solid to describe the business creation especially for one report. However, the construction of passenger profiles is the crucial breach of the confidentiality, and the e-ticket fare scheme should prevent the tracking of the passenger. In 2006, Heydt-Benjamin et al. [1] introduced a scheme of privacy for public transportation. But in their scheme the issuer cannot trace the trips, thus the new credential is required for each trip, this means that there is the important additional charge in such transport scheme, where the entries and exits of the scheme have to be as rapid as possible. The credential renewal needs more issuer construction that is costly, since it should manage the high number of credentials. However, the first scheme using the latest trends in the direction to utilize mobile phones is proposed in 2008 by Madlmayr et al. [2]. Therefore, we can state that the mobile phone is the passenger requirement in the e-ticket fare scheme. In this paper, we proposed scheme which gives revocable anonymity and intractability. Also, this scheme has been designed to employ the personal mobile phone of the passenger and the passenger do not want to get the new credential each time if he wants to make the trip, since the credential renewal means the additional cost.
In 2010, Vives-Guasch et al. [3] introduced a fare collection scheme, in their scheme the passenger cannot able to alter the direction of the transfer without exiting the service. Also, in 2012, Andreu Pere Isern-Deya et al. [4] presented a Fare collection system for revocable anonymity for users which is not involving the requirements for the extensions. It means that, they should check out along with their direction. In 2014, Ghada Arfaoui et al. [5] introduced another scheme related to privacy-preserving of mobile for transport systems. Their scheme needed to put scheme exits separated by direction. Also, in 2016 Magdalena Payeras et al. [6] designed two schemes to get anonymity in transferable e-ticket. Their schemes also cannot modify the direction. In the proposed scheme, we extend the work to let time-typed scheme solve such problems.
The scheme applies the group signature system to check if the passenger is the proper member of the selected group of passenger. The group signature system used is illustrated in Section 4. Then, we consider the time-typed scheme in Section 5. Section 6 considers the security discussion of the scheme. Lastly, the conclusion is illustrated in Section 7.
The notations used are as follows:
p, q: prime numbers
pk: group public key
sk: group secret key
rt: group of revocations
P: passenger
eP: passenger pseudonym for payment
dP: inverse key of eP private
b: key base
ri: ith arbitrary number
si: key of ri
ci: ith challenge for P to prove authorship of eP
wi: challenge ci reply by P
sP: probabilistic encryption of eP
Ti: ith timestamp
v: verification key
hv: hash image of key v
SE (c): digital signature of c generated by the entity E
ss: source service issuer identifier
t'in: entry ticket, signed by ss
sb: serial number generated by ss for tin
as: arrival station
t'in : exit ticket, signed by as
cf: challenge and fare, signed by as for P
fc: fare computation function
fp: fare to be paid
ds: destination service issuer identifier
pe: probabilistic encryption of P
pn: probabilistic encryption of as
eg: entity generates passenger
pa: payment acceptance signed by eg
pr: payment rejection signed by eg
es: entry station ss identifier
τ1: entry timestamp, time entry system
cs: commitment signed by P
Ds (tin): digital signature content signed by es
tin.sb: serial number sent by P
ts: target station
τ 2: payment timestamp, it means time exit ticket
Ds(tout): digital signature content signed by as
We utilize the short group signature [7] system to check that the passenger is the right member of the selected group of passenger. Observe that the notations in this part are explicit for the clarification of the used definitions.
The proposed scheme uses bilinear groups G1 and G2 with relevant generators a1 and a2. Assume that (G1, G2) are the Linear assumption. The scheme utilizes the bilinear map e: G1 × G2=GT and the secure hash function H: {0,1}=Zp. The public keys are a1, z1, z1, b ∈ G, and a2, d ∈ G. Hence, d=au2 for private u ∈ Z. In the proposed scheme we use the following algorithms.
• KeyGenG (n). This algorithm has one input n. The steps of the algorithm are as follows:
1. Choose an integer b ∈ G1 ;
2. Select two integers 
3. Choose two integers z1, z2 ∈ G1 where 
;
4. Choose an integer 
;
5. Compute the integer 
;
6. Generate for every passenger Pi where 1≤i ≤n a key (wi, yi) as follows:
1. Choose 
;
2. Compute 
;
7. The key u is then a secret master key of a group key.
• 
. This algorithm takes the parameters, a group public key 
, the secret passenger key sk[i]=(wi, yi) and the message m ∈{0,1}*.
Find the signature of information σ=(A1, A2, A3, c, sv1, sv2, sx, sδ1, sδ2). The steps of the algorithm are as follows:
Step 1
The descriptions of this step are as follows:
1. choose two integers 
2. find an encryption of 
3. compute the number 
4. compute the value 
Step 2
The descriptions of this step are as follows:
1. Choose the integers 
2. Find the numbers:
Step 3
The descriptions of this step are as follows:
1. find 
Step 4
The descriptions of this step are as follows:
1. Find the numbers:
Step 5
The descriptions of this step are as follows:
1. The result is 
• 
This algorithm provides a group public key 
the message m and the group signature 
check that σ is the valid signature of information.
1. Re-get 
2. verifies that: 
• Open 
. This algorithm is employed to trace the signature inside
the group. It is just on hand for the group director, as he is the owner of the msk
master key, and gets all the pairs 
. Suppose a group public key pk=(a1, a2, b, z1, z2, d) a group master secret key msk=(f1,f2) both with m and a signature 
. Then, retrieve a passenger A by 
. If the group director is known the components wi of the passenger secret keys, he can search for the passenger index similar to an
identity A retrieved from the signature.
• SignLinkable 
. This is the linkable signing algorithm to be applied
in the scheme. Assume that the group public key pk, the secret customer key
sk[i] and the message m. Find the signature of information. To use such
algorithm properly, do the following:
First: Employ standard Sign 
Create the linear encryption of 
for 
; assume
the message m, sign it and result the signature 
where
Second: Use SignLinkable 
Employ the same pair (v1, v2) creating the same linear encryption of A than in the first time: 
Determine the message m′ , sign it and yield the signature
Observe that it can provable some signatures that are created by the same passenger,
as the knowledge (A1,A2,A3) is public within the same signature. Also, the arbitrary
values 
should be dissimilar to preceding instances, namely 
to not disclose knowledge.
• VerifyLinkable 
. The algorithm requires two signatures as input 
and 
and result true or false based on the signatures have created by a same signer false name 
First, we start to describe the requirements of the e-ticket fare scheme
The subsequent security requirements have to be certain in any proposed scheme:
1. Authenticity: each ticket should be produced by its authorized provider.
2. Non-repudiation: a passenger cannot repudiate the issue of one of its tickets.
3. Integrity: after the ticket is produced, cannot be adjusted.
4. Validity period: each ticket has a validity period item to verify if it is in use or not. Every used ticket will saved in the file until its validity period is expired.
5. Non-double-spending: The validity time of each ticket is verified. If the verification is true, the scheme says that a ticket is not in the file of used tickets based on its serial number. Such verification guarantees that the ticket does not employs more than one time.
6. Revocable anonymity: the scheme should promise the customer anonymity to receive approval of the passenger community, but the scheme and the public authorities favor non-anonymity because of control and security reasons. So, the midway solution is revocable anonymity for passenger. If the passenger behaves badly, his anonymity is called.
7. Non-traceability: the supplier can only trace the entry of the passenger with its related exit, but in no way can trace diverse trips of the same passenger.
The common time-typed fare is the daily, weekly or monthly employed by passengers to use the public transport, generating the single ticket which lets the passenger to use it. However, we will denote to the time-typed fare scheme if the money to be paid by the passenger based on the time period does employ. Therefore, in this case, the suitable timestamp should be created if the passenger becomes inward and outward movement of the scheme. The dissimilarity between the current time and an initial timestamp will determine a fare which should be paid to the service issuer.
Time-typed fares are most suitable in locations where the most related parameter of the service provided the time. For instance, bus services, taxi services, tube services and parking places services. Therefore, time-typed costing methods will need time accounts instead of pay per boarding trip. Thus, in this example the scheme has to:
1. Generate the appropriate timestamp if the new ticket is released.
2. The timestamp generates the time-window if a customer has the right to employ the service fare.
3. The time-window has the start-date and the expiry-date that writes the ceiling-time of the service fare.
4. The price to be paid is relative to the time-period that a customer has employed the fare-service. The longer is the time the costly is a ticket.
5. The timestamp should be verified the scheme exit to calculate the service cost.
Now, we explain the proposed time-typed e-ticket fare scheme that gives anonymity to the passenger by the application of group signatures [8] for group-transport services. We explain the participants included in the scheme, the security requirements to be certain, the details which is involved into the entry and exit tickets, and finally the phases by which the scheme contains.
The subsequent players are included in the proposed scheme:
1. Passenger P. Entrances to a transport system then pay for a service at an exit. Passenger P does these services by means of his mobile phone.
2. Issuers (ss departure station, as arrival station): checkpoint that runs the tickets used by passenger P. The price to be paid by P is calculated by as in proportion to parameters determined, time-typed fares.
3. Payment TA eg: runs passenger payments if they exit from a scheme.
4. Group TA ed: runs a revocation list and group keys. It can call passenger anonymity in case of badly behaved.
In the scheme, there are four protocols which are as follows:
1. Initialization Protocol
The ed creates the group keys and revocation list. This setup is performed once
at first. ed runs KeyGenG(n) that generates the group of fixed length n, yields 
, such that pk is a group public key, sk[i] is a secret key for
every passenger Pi, rt[i] is a revocation list, (a, p, q) are public keys, with a is a
public key, and (p,q) prime numbers such that p=2q+1, where 
respectively. Also, every service issuer creates its key pair and illustrates its
public key. The secret group key sk[i] is released if passenger are listed in the
group.
2. Passenger Registration Protocol
The passenger P also registers at eg by the pseudonym that is used just for payments, he receives the group key pair. In the proposed scheme, eg is the entity that generates passenger and service issuer accounts. Such entity deals with the payment related messages and promises the payment for official transactions consistent with the scheme requirements.
The passenger P registers in the group TA ed and gets the group key pair (pk,
sk[i]). Now, the passenger consent that their identity are revealed when they are
not truthful, or when the judge needs to cancel their anonymity. Then, P also
registers anonymously to the payment TA eg by an authorization of ed; a
passenger owns the pseudonym eP that is the exponentiation of the arbitrary
integer dP∈Zq, with 
mod p; the eP is proved to eg and authenticated by
Schnorr zero-knowledge proof [8] proving of d P without revealing that private.
Therefore, confidentiality is sealed for passenger, but this anonymity can be
called by ed when needed. The passenger registration protocol is described as
follows:
Generate pseudonym: The passenger P should do the following:
1. select the pseudonym as the random integer dP ∈ Zq ;
2. find the value mod p;
3. pass the identity Pi to the group TA ed;
4. pass the certificate CertPi to the group TA ed;
5. pass the signed message SignP(eP) to the group TA ed;
Key issue: ed should do the following
1. pass the group key pair (pk, sk[i]) to a passenger P;
2. pass the public parameters (a, p, q) to a passenger P;
3. pass the signature Signed (eP) to the passenger P;
Starting ZKP: P should do the following
1. Select an arbitrary integer 
2. Find 
mod p;
3. Pass 
to the payment TA ed;
Challenge generation: eg should do the following
1. Select the integer 
;
2. Pass g2 to P ;
Proof generation: P should do the following
1. Find the Schnorr ZKP;
2. Compute 
3. Pass g3 to eg;
Check pseudonym: eg should do the following
1. Check that 
;
Scheme entry: the passenger joins in the departure station and creates the group signature that confirms he is the valid scheme group member, while his identity is not revealed. If such signature is passed to the service issuer ss, he receives the entry ticket from ss that will be illustrated in the departure station.
If P has properly keyed the scheme, the entry ticket tin is then received. The tin will be later employed to authorize a passenger to pay the considered fee. The scheme entry is described as follows:
Obtain service: The passenger P should do the following
1. select a random integer 
2. find 
3. find 
;
4. select a random integer 
;
5. find a hash function of: 
;
6. determine 
and signs it with sk[i];
7. passenger secret group key is 
;
8. pass 
to ss;
Generate ticket: The source service issuer ss should do the following
Check entry: passenger P should do the following
1. Checks a signature of 
;
Scheme Exit
The passenger does the weak authentication to an arrival checkpoint as and proves an entry ticket. as then computes the charge to be paid. The passenger has to accept the price and passes this knowledge safely to eg within his payment pseudonym authentication, just eg has information of such pseudonym, as can not reveal that knowledge. Then, eg costs to P account. When the entire process is right, the passenger receives the exit ticket, which is the evidence shows that the passenger has followed the scheme properly. If the passenger exits the scheme, then passes the ticket entry tin to the arrival service supplier as, and the charge to be paid is computed. If P acts properly, the exit ticket tout is received, and can be later presented as the proof of payment, involving that the scheme had been followed properly. The scheme exits and describe as follows:
Prove ticket: passenger P should do the following
1. encrypt L3
2. pass 
to as;
Check ticket: The service issuer as should do the following:
1. Check a signature of t*in which is calculated by ss;
2. Check that 
, shows that P is a correct owner of the ticket tin;
3. Check that 
had not been used before;
4. Select the timestamp τ2 where τ2 ≤ τ2 ;
5. Compute the charge to be paid based on the elapsed time between related time stamps 
thus, in this example, 
is the function
designed to compute the charge between two stations on the time-typed fare
scheme.
6. Select the challenge 
;
7. Compute 
;
8. Sign it 
9. Pass λ* to P, in case of challenge λ is employed by P as the evidence to show that he has exit at τ2;
10. Compute 
Set payment: passenger P should do the following:
1. Check a signature of λ
* which is calculated by as;
Passing payment information: The service supplier as should do the following:
1. Repost eP and yas to the payment TA eg;
Check payment: eg should do the following:
Set exit: The service issuer as should do the following:
Verify ticket: passenger P should do the following:
1. Check a signature of 
Through the scheme exit protocol, as cannot follow the protocol because of various causes. For example as may fail, produce errors, or entrust corrupt activities. Due to that, the sincere passenger will receive the illegal service. To solve such problem, the protocol could face two passenger assumptions.
1. Assumption 1: Wrong λ* is received
Through the scheme exit protocol, customer P can pass the validation data (tin,k), but as could behave badly and passes the incorrect λ. For example, the message has the inexact τ2 to P or, as is not passed it. Then, such passenger can claim to receive the valid λ* to payment AT eg by the subsequent steps:
Step 1 request: The passenger P should do the following:
Step 2 reply: The payment TA eg should do the following:
Step 3 resume: The scheme does the following:
1. The scheme exit, protocol keeps on as normal.
1. Assumption 2: Wrong t*out is received
Through the scheme exit protocol, P can pass the validation knowledge 
, but as
can behave badly and passes the wrong t*out to P or just denies to pass it. Then, the
passenger can communicate with a payment TA eg and he can claim to receive the valid t*out by the subsequent steps:
Step 1 request: The passenger P should do the following:
Step 2 reply: The payment TA eg should do the following:
Step 3 resume: The scheme does the following:
1. The scheme exit, protocol keeps on as normal.
Remarks
In both assumptions, the payment TA eg has to:
1. Inform as of its bad behavior or message problems with passenger.
2. Notify as of possible more actions if such problem continues.
Through the scheme exit protocol, P cannot follow the protocol because of various causes. For example, P may be unsuccessful, make errors, entrust corrupt actives. Due to that, the supplier will receive the illegal service. To solve such problem, the proposed protocol can face two supplier assumptions.
1. Assumption 1: Wrong 
is received
Through the scheme exit protocol, as receives the first step of a checking message , but this message cannot be true. Then, the service supplier can claim to reveal
customer identity by the subsequent steps:
Step 1 request: The destination service issuer as should do the following:
1. Pass to ed;
Step 2 request passenger: The passenger P should do the following:
1. Pass also to ed, to evade false complaints;
Step 3 reply: The group TA ed should do the following when P is not passed the needed items:
1. Assumption 1: Wrong eP is received
Through the scheme exit protocol, as and eg gets the last step of the checking message eP, but this message cannot be true. Thus, the service issuer can claim to reveal passenger identity by the subsequent steps:
Step 1 request: The payment TA eg should do the following:
Step 2 Issuer information: The destination service issuer as should do the following:
1. Pass 
Step 3 request passenger: passenger P should do the following:
Step 4 reply: The group TA ed should do the following:
The proposed scheme achieves the security requirements described in section 4. The achievements are as follows:
The Authenticity
The formation of fake ticket is totally not practical these days. Since, the tickets are
signed 
, also the posted information previous
to a payment 
. When the illegal passenger can generate the valid ticket
(entry or exit) without information of the secret keys neither of ss nor as, it can create
digital signature while pretend to be such issuers. Assume that we use the digital
signature scheme, this process is not practical. Conversely, the passenger passes the
verification message signed with his group secret key 
. Such signature
ensures that a message is real and is issued by the valid passenger.
Non-repudiation
The issuer of the ticket cannot repudiate the release of such ticket. The ticket is signed by its official provider and, by allowing for that the applied signature scheme is safe, such operation can be only done by these issuers. Therefore, the issuer identity is connected to the ticket and, for the characteristics of the e-signature scheme, that issuer cannot repudiate its compilation. The same happens with a group signature scheme, when an identity is revealed, a message compilation can be checked.
Integrity
Once the ticket is generated cannot be changed. Assume that a hash function is secure and its inverse function is totally impossible these days. If ticket content is changed, the checking of the signature will be wrong. To exceed the checking, the signature will be required to be recreated from the new ticket content. Such operation is totally impossible these days in the most present machines.
Validity Period
The ticket is not more valid when its validity time Tv is expired. The target station as
extradites a ticket from the passenger to be checked. In this verification, the present
time is compared with a validity time Tv of an entry ticket 
which is signed by ss. The
information regarding a passenger identity is encrypted by a payment TA public key.
The authorized issuers (ss and as) cannot get access to such information since they
require the secret key of the TA. In the proposed scheme, passengers calculate the
group signature 
which verify a signer is the valid group member.
When we consider the characteristics of a group signature scheme, an issuer cannot
reveal an identity of a signature generator. In case of debatable circumstances, an
identity of a passenger which signed the content might be revealed during the
verification of both payment TA eg and the group TA ed.
The ticket is anonymous. The passenger is anonymous by an authorized issuer through
a payment protocol. The content regarding a payment is encrypted and just a payment
TA can get access to it. The authorized issuer is outside to the payment, and just
receives the payment verification from the payment TA eg. So, eg has information
concerning eP from the pair (dP, eP) such that 
mod p, which identifies him as the
valid passenger. Then, the passenger authenticates by showing information of dp by
Schnorr ZKP.
Non-traceability
The group signatures done by the same passenger should be untraceable by the authorized issuers or other bodies outside to the scheme. The group signature in ref. [7] by Boneh, et al. [8] applies the probabilistic signature scheme. It is not likely to guess the encrypted message given the certain message. This lets difficultly between various group signatures done by the same passenger.
Non-double-spending
The scheme prevents ticket double-spending. When the passenger attempts to doublespend an entry ticket, the serial number is signed as already used. When such passenger bad behavior is showed, the group TA ed can add in such passenger to a revocation list.
Conspiring Attack
The time-typed fare collection scheme illustrated in section 5 cannot be attacked by conspired passengers. The conspiring attack illustrated in 6.2 using the swap of entry tickets is not applicable to time-typed because the passengers do not get any gain of the exchange. The fare is computed using the entry timestamp thus when the passengers swap their tickets the charges are the same and one of the passengers will pay more than her actual ticket. Therefore passengers are discouraged to swap tickets.
We have introduced a secure e-ticket fare scheme which is tailored for huge passengers transport. We have accomplished the scheme that can be tailored to time-typed or distance-typed charge with somewhat modifications. The utilize of group signatures schemes lets the passenger authentication whereas it is preserved his privacy. But, the identity of passengers can be reveal in case of the passenger bad behavior. The proposed scheme does not need to get the new credential each time the passenger links in the scheme to get intractability and to avoid tracking and profiling. Thus, the proposed scheme resistant from attacks of conspired passenger.
The future work leaves to the direction and extend the new communication tools more appropriate for e-commerce systems such area of communication, which is planned mainly for use in mobile phones.
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