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4 On Rejsekortet are even capable of running a small cryptographic cipher, plus implementing access conditions for separate portions of the on-board storage on the card. 1.2.2 The infrastructure of Rejsekortet Rejsekortet comprises of three basic entities, namely the cards, the terminals and the back-office. Cards are held by the commuters using the system, and terminals are installed on stations and in buses. Not much is known about communication with the back-office, but it is certain that the terminals synchronize at least their event log (storing special “Transaction IDs” specific to the cards) with a central database, either live or on a buffered basis. The buffered readers would be installed in buses, and only occasionally transmit their buffer with the back-office. One could imagine a solution where buses would synchronize at some traffic centre, such as the town hall square for the Copenhagen buses, in order to reduce costs. 1.2.2.1 Check-in and check-out When a user wants to travel somewhere with a Rejsekort, he/she will “check in” on the designated terminals at the station of origin. This will create a certain data element on the card describing the time and place of the check-in, and write that to the card. Any intermediate stops require another check-in, in order for the system to calculate the fare correctly—these check-ins will also be stored on the card. If the card is checked by a ticket conductor during the trip the scanner will parse this data structure and check for these “check-ins.” After the trip the user checks out at the terminals on the station. The terminal presents the fare and draws the money from the card. An important thing to note is that the card stores this information, so in order to restrict tampering it implements some systems preventing this abuse, see section 1.3. 1.2.2.2 The different kinds of cards There are three different types of Rejsekort, each aimed at different kinds of users. This gives the system an advantage over the conventional punching card system currently in use in Denmark (“klippekort”), because it is possible to
1.2 Technology and card layout 5 make very precise profiles of each card’s usage patterns, etc. The three different types are: • Personalized: These cards are personal, and the name and photo of the owner is printed on the card. This will likely be the standard card that commuting Danes will use. • Pseudo-anonymous, also known as “Rejsekortet Flex:” This card is flexible in the sense that it can be used by anyone, not just the owner. This would for example be used in companies that pay for the employees’ occasional travel, or parents who own a card that their children use. • Anonymous: This card is likely targeted for tourists and other travellers. It is completely anonymous and can be used by whoever possesses it. This card is currently not marketed on the website for Rejsekortet, which only reinforces the thesis of it being for tourists. Never the less, it can be assumed that these cards are possible to get hold of once the system is deployed nationwide. Source: [8]. There are different grades of discounts available in the system. To encourage people to use the personal version of the card, the highest level of discount attainable is only available in the fully personalized version. Flex users get “zero to medium” discount, and the same goes for anonymous users, [8]. 1.2.2.3 Terminals This thesis deals with three different types of terminals used in the Rejsekort system. These are: • Check-in terminals are used on stations when a user wants to commence a travel. • Top-up terminals are used for loading money from a credit card to a Rejsekort. These are also situated on stations, and do not require the user to hold the card in front of a reader. Instead the user is supposed to put the card into a slot. • Conductor terminals are used by conductors on buses or trains to check if the users have checked-in.
Page 1 and 2: Cryptanalysis of Rejsekortet Jens C
Page 3: 3 Abstract. This bachelor thesis an
Page 7: Resumé Denne bachelorafhandling er
Page 10 and 11: vi Glossary Rejsekort(et) Danish fo
Page 12 and 13: viii
Page 14 and 15: x CONTENTS 4.3 Other improvements .
Page 16 and 17: 2 On Rejsekortet Disclaimer: This r
Page 20 and 21: 6 On Rejsekortet 1.2.3 Mifare Mifar
Page 22 and 23: 8 On Rejsekortet 1. Reader sends a
Page 24 and 25: 10 On Rejsekortet Time of transacti
Page 26 and 27: 12 On Rejsekortet Figure 1.3: The C
Page 28 and 29: 14 On Rejsekortet 1.3.2.1 CBC-MAC C
Page 30 and 31: 16 On Rejsekortet
Page 32 and 33: 18 Security analysis and threat mod
Page 38 and 39: 24 Attacks on Rejsekortet 3.1 Rollb
Page 40 and 41: 26 Attacks on Rejsekortet 3.2 Attac
Page 42 and 43: 28 Attacks on Rejsekortet and cumbe
Page 44 and 45: 30 Attacks on Rejsekortet hash valu
Page 46 and 47: 32 Attacks on Rejsekortet 3.2.4 Int
Page 48 and 49: 34 Attacks on Rejsekortet 3.2.5 App
Page 50 and 51: 36 Attacks on Rejsekortet 3.2.6.2 T
Page 52 and 53: 38 Attacks on Rejsekortet Language
Page 54 and 55: 40 Attacks on Rejsekortet It is not
Page 56 and 57: 42 Attacks on Rejsekortet specifica
Page 58 and 59: 44 Attacks on Rejsekortet might pro
Page 60 and 61: 46 Attacks on Rejsekortet that the
Page 62 and 63: 48 Attacks on Rejsekortet
Page 64 and 65: 50 Improvements 4.1.1 New MAC algor
Page 66 and 67: 52 Improvements functions tend to b
Page 68 and 69:
54 Improvements
Page 70 and 71:
56 Conclusion of the pre-computatio
Page 72 and 73:
58 Related research Sector 04 - UNK
Page 74 and 75:
60 Mail correspondence enquire abou
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62 Mail correspondence * Kodningspr
Page 78 and 79:
64 Mail correspondence Som ingeniø
Page 80:
66 BIBLIOGRAPHY [9] Philippe Oechsl
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