EP1035517B1 - Method for the protection of a security module and arrangement for implementing said method - Google Patents

Description

The invention relates to a method for protecting a security module, according to the type specified in the preamble of claim 1, and an arrangement for carrying out the method, according to the type specified in the preamble of claim 3. Such a postal security module is in particular for use in a franking machine Mailing machine or computer with mail processing function suitable.

Modern franking machines, like those from the US 4,746,234 known thermal transfer postage meter, employ a fully electronic digital printing device. Thus, it is possible in principle to print any text and special characters in the franking stamp printing area and any or a cost center associated advertising clause. For example, Applicants' T1000 meter has a microprocessor surrounded by a secure housing having an opening for delivering a letter. For a letter feeder, a mechanical letter sensor (microswitch) transmits Pressure request signal to the microprocessor. The franking imprint includes previously entered and stored postal information for conveying the letter. The control unit of the franking machine carries out a software billing, exercises a monitoring function, possibly with regard to the conditions for a data update, and controls the reloading of a port value credit.

For the abovementioned thermal transfer franking machine has already been in US 5,606,508 ( DE 42 13 278 B1 ) and in US 5,490,077 proposed a data entry option using smart cards. One of the smart cards loads new data into the postage meter machine and a set of further smart cards allows a setting to be made according to stored data by inserting a chip card. The data loading and the setting of the franking machine can thus be more convenient and faster than by keyboard input. A franking machine for franking mail is provided with a printer for printing the postage stamp on the mail, a controller for controlling the printing and peripheral components of the postage meter, a bill unit for settling postage, at least one nonvolatile memory for storing postage data , equipped with at least one non-volatile memory for storing safety-relevant data and with a calendar / clock. The non-volatile memory of the safety-related data and / or the calender / clock is usually powered by a battery. In known franking machines, security-relevant data (cryptographic keys and the like) are saved in nonvolatile memories. These memories are EEPROM, FRAM or battery backed SRAM. Known franking machines often also have an internal real time clock (RTC), which is powered by a battery. For example, are known encapsulated modules containing integrated circuits and a lithium battery. These modules must be replaced and disposed of at the end of the life of the battery as a whole. From an economic and ecological point of view, it is better if only the battery needs to be replaced. For this purpose, however, the security case must be opened and then closed again and sealed, because the security against fraud is essentially based on the secure housing, which encloses the entire machine. The applicant was in EP 660 269 A2 ( US 5,671,146 ) be ready proposed a suitable method for improving the safety of franking machines, in which a distinction is made between an authorized and unauthorized opening of the security housing.

Any required repair of a franking machine is then difficult on site, if the access to the components is difficult or limited. In the case of larger mail processing machines or so-called PC frankers, the secured housing will in future be reduced to the so-called postal security module, which can improve the accessibility to the other components. To economically exchange the battery of the security module, it would also be desirable that these be relatively simple can be replaced. For this purpose, the battery must be outside the security range of the franking machine. However, when the battery terminals are accessed from the outside, a potential attacker is able to manipulate the battery voltage. Known battery-powered SRAM and RTC have different requirements with regard to their required operating voltage. The voltage required to hold data from SRAM is below the required voltage for operating RTC. This means that decreasing the voltage below a certain threshold will result in undesired behavior of the components: the RTC will stop, the time stored in SRAM cells, and the memory contents of the SRAM will be preserved. At least one of the security measures, for example long-time watchdogs, would then be ineffective on the franking machine side. The term "long-time watchdogs" is understood to mean the following: The remote data center specifies a time credit or a period of time, in particular a number of days, or a specific day up to which the franking device can report by means of a communication connection. After unsuccessful expiration of the time credit or the deadline, franking is prevented. Under the title: Procedure and Arrangement for the Generation and Verification of a Security Imprint has already been published in the EP 660 270 A2 ( US 5,680,463 ) a method is proposed to determine the probable period until the next credit recharge, which is considered by a data center that postage meter as suspect, which does not report in due time. Suspended franking machines are communicated to the postal authority, which monitors the mail flow for letters franked by suspect franking machines. A lapse of the time credit or the deadline is already determined by the franking device and the user is prompted to perform the overdue communication.

Security modules are already known from electronic data processing systems ago. To protect against burglary in an electronic system is in EP 417 447 B1 already proposed a lock, which includes power supply and signal detection means and shielding in the housing. The shielding means is made of encapsulating material and conductive means to which the power supply and signal detection means are connected. The latter responds to a change in the line resistance of the line means. In addition, the security module contains an internal battery, a voltage switch from system voltage to battery voltage, a power gate and a short-circuit transistor as well as other sensors. When the voltage falls below a certain limit, the Power Gate responds. If the line resistance, temperature or radiation is changed, the logic will react. By means of the power gate or by means of the logic, the output of the short-circuit transistor is switched to L level, whereby a memory stored in the cryptographic key is deleted. However, the life of the non-replaceable battery and thus of the security module for use in franking devices or mail processing machines is too small.

A larger mail processing machine is, for example, the JetMail®. A franking print is here produced by means of a stationary ink jet printhead in a non-horizontal approximately vertical letter transport. A suitable design for a printing device was already in the DE 196 05 015 C1 proposed. The mailing machine has a meter and a base. If the meter is to be equipped with a housing so that components are more easily accessible, then it must be protected by a postal security module fraud attempts, which at least performs the settlement of postal fees. To exclude influences on the program, has already been in the EP 789 333 A2 under the title: Postage meter proposed to equip a security module with an Application Specific Integrated Circuit ASIC, which has a hardware Abrecheneinheit. The user circuit also controls the print data transfer to the print head.

The latter would only be required if unique impressions were created for every mail item. A suitable method and arrangement for generating and checking a security impression is, for example, in US 5,680,463 . US 5,71 2,916 and US 5,734,723 been proposed. A special security marking is generated electronically and embedded in the printed image.

Further measures to protect a security module against an attack on the data stored in it were also in the not pre-published German applications 198 16 572.2 and 198 16 571.4 proposed. With a large number of sensors, the power consumption increases and a safety module, which is not always supplied by a system voltage, then draws the current required for the sensors from its internal battery, which also depletes the latter at an early stage. The capacity of the battery and the power consumption thus limit the life of a security module.

Like many other products, franking machines are also modular. This modularity allows the exchange of modules and components for various reasons. Thus, e.g. defective modules are replaced and replaced by checked, repaired or new modules. Since the utmost care is required in the exchange of assemblies containing safety-relevant data, the replacement usually requires the use of a service technician and measures that prevent its functioning in case of improper use or unauthorized replacement of a security module. The latter is very expensive.

The invention has for its object, with little effort to ensure protection against an unauthorized manipulated security module when the security module is arranged interchangeable. The exchange should be possible by anyone in the simplest possible way.

The object is achieved with the features of the method according to claim 1 and with the features of the arrangement according to claim 3.

The invention is based on the functional units to determine the exchange and use of a security module of a postage meter, mail processing device or similar device to To provide the users of the various devices with a guarantee about the correct functioning of the security module and thus of the entire device. An exchange of a safety module is detected at least and subsequently signaled as a condition if the safety module is plugged in again and supplied with a system voltage. The changes in the state of the security module are detected by means of a first functional unit and by means of a battery supplied by a detection unit, which has a resettable latching. The first functional unit can evaluate the respective state when it is supplied with system voltage again. The advantages are a quick response to changes in the state of the security module and a low battery power consumption of the circuit of the detection unit during the non-supply of the security module with the system voltage.

• ● Überwachung des sachgemäßen Gebrauchs oder Austausches des Sicherheitsmoduls mittels einer ersten, zweiten und dritten Funktionseinheit,
• ● Löschen von sensitiven Daten aufgrund eines unsachgemäßen Gebrauchs oder Austausches mindestens mittels der zweiten Funktionseinheit,
• ● Sperren der Funktionalität mittels der dritten Funktionseinheit während eines Austausches des Sicherheitsmoduls,
• ● Reinitialisieren mittels der ersten Funktionseinheit von zuvor gelöschten sensitiven Daten nach sachgemäßem Austausch des Sicherheitsmoduls,
• ● Wiederinbetriebnahme durch Freischalten der Funktionseinheiten des Sicherheitsmodules.

At least the improper use of a security module should be assumed with every replacement, in which not only the system voltage is missing, but also the replaceably arranged battery is removed. So that the replacement of the lowest possible qualified personnel and in the future can even be performed by the user, another function unit monitors the power failure when replacing the battery, the other functional unit first deletes sensitive data and thus restricts the further use of the security module or even in derogation. The first functional unit enforces a later re-commissioning contact the security module with a remote data center to unlock at least one functional unit. If the security module has been replaced properly, the sensitive data will be reinitialized during the restart. To establish contact methods with a digital or analog transmission link can be used. The procedure for protecting a security module involves the following steps:

• ● monitoring the proper use or replacement of the safety module by means of a first, second and third functional unit,
• Deleting sensitive data due to improper use or replacement at least by means of the second functional unit,
• ● locking the functionality by means of the third functional unit during an exchange of the security module,
• ● reinitialization by means of the first functional unit of previously deleted sensitive data after proper replacement of the safety module,
• ● Recommissioning by activating the functional units of the safety module.

It is envisaged that the reinitialization in connection with communication by means of a remote data center is performed by the first functional unit after a dynamic mating detection has been carried out successfully, during which information is exchanged during the detection of the first functional unit via a current loop of the interface unit Transmission proves the proper installation of the safety module. The activation of functional units of the safety module is done by resetting them. The first functional unit is a processor connected to the other functional units which is programmed to determine the respective status. The second functional unit is a voltage monitoring unit with resettable latching and the third functional unit is a non-latching detection circuit with resettable latching.

Figur 1,

Blockbild und Interface des Sicherheitsmoduls,

Figur 2,

Blockschaltbild der Frankiermaschine,

Figur 3,

Perspektivische Ansicht der Frankiermaschine von hinten,

Figur 4,

Blockschaltbild des Sicherheitsmoduls (zweite Variante),

Figur 5,

Schaltbild der Detektionseinheit,

Figur 6,

Seitenansicht des Sicherheitsmoduls,

Figur 7,

Draufsicht auf das Sicherheitsmodul,

Figur 8a,

Ansicht des Sicherheitsmoduls von rechts,

Figur 8b,

Ansicht des Sicherheitsmoduls von links.

Advantageous developments of the invention are characterized in the subclaims or are presented in more detail below together with the description of the preferred embodiment of the invention with reference to FIGS. Show it:

FIG. 1,

Block diagram and interface of the security module,

FIG. 2,

Block diagram of the franking machine,

FIG. 3,

Perspective view of the franking machine from behind,

FIG. 4,

Block diagram of the security module (second variant),

FIG. 5,

Circuit diagram of the detection unit,

FIG. 6,

Side view of the security module,

FIG. 7,

Top view of the security module,

FIG. 8a,

View of the security module from the right,

FIG. 8b,

View of the security module from the left.

In the FIG. 1 is a block diagram of the security module 100 with the contact groups 101, 102 for connection to an interface 8 and with the battery contact terminals 103 and 104 of a battery interface for a battery 134 shown. Although the security module 100 is potted with a hard potting compound, the battery 134 of the security module 100 is interchangeably disposed outside of the potting compound on a printed circuit board. The circuit board carries the battery contact terminals 103 and 104 for connecting the poles of the battery 134. By means of the contact groups 101, 102, the security module 100 is plugged into a corresponding interface 8 of the motherboard (motherboard) 9. The first contact group 101 communicates with the system bus of a control device and the second contact group 102 serves to supply the security module 100 with the system voltage. Via the pins P3, P5-P19 of the contact group 101 run address and data lines 117, 118 and control lines 115. The first and / or second contact group 101 and / or 102 are / is designed for static and dynamic monitoring of the plugged in the security module 100. About the pins P23 and P25 of the contact group 102, the supply of the security module 100 is realized with the system voltage of the motherboard 9 and the pins P1, P2 and P4, a dynamic and static non-detection detected by the security module 100.

The security module 100 has, in a manner known per se, a microprocessor 120 which contains an integrated read-only memory (internal ROM) with the special application program (not shown), which is approved for the franking machine by the postal authority or the respective mail carrier. Alternatively, a conventional read-only memory ROM or FLASH memory can be connected to the internal data bus 126.

The security module 100 has, in a manner known per se, a reset circuit unit 130, a user circuit ASIC 150 and a logic PAL 160 which serves as the control signal generator for the ASIC. The reset circuit unit 130 or the user circuit ASIC 150 and the logic PAL 160 as well as possibly further - not shown - memory are supplied via the lines 191 and 129 with system voltage Us +, which is supplied from the motherboard 9 with the franking device turned on. In the EP 789 333 A2 The essential parts of a postal security module PSM have already been explained, which implement the functions of billing and hedging the postal fee data.

The system voltage Us + is also applied via a diode 181 and the line 136 at the input of the voltage monitoring unit 12. At the output of the voltage monitoring unit 12, a second operating voltage U _{b + is} supplied, which is available via the line 138. When the franking device is switched off, not the system voltage Us +, but only the battery voltage Ub + is available. The negative terminal battery contact terminal 104 is connected to ground. From the battery contact terminal 103 lying on the positive pole, battery voltage is supplied via a line 193, via a second diode 182 and the line 136 to the input of the voltage monitoring unit. As an alternative to the two diodes 181, 182, a commercial circuit can be used as Spannungsumsohalter 180.

The output of the voltage monitoring unit 12 is connected via a line 138 to an input for this second operating voltage U _{b + of} the processor 120, which leads at least to a RAM memory area 122, 124 and there guarantees non-volatile storage as long as the second operating voltage U _{b +} in the required height is applied. The processor 120 preferably includes an internal RAM 124 and a real-time clock (RTC) 122.

The voltage monitoring unit 12 in the security module has a resettable latching, which can be queried by the processor 120 via a line 164 and reset via a line 135. For a reset of latching, the voltage monitoring unit 12 switching means on The reset is not triggered until the battery voltage has risen above the predetermined threshold.

The lines 135 and 164 are each connected to a pin (pins 1 and 2) of the processor 120. Line 164 provides a status signal to processor 120, and line 135 provides a control signal to voltage monitoring unit 12.

The line 136 at the input of the voltage monitoring unit 12 also supplies an unplugged detection unit 13 with operating or battery voltage. The unplugged detection unit 13 outputs on the line 139 a status signal to a pin 5 of the processor 120, which gives an indication of the state of the circuit. The processor 120 queries the state of the unplugged detection unit 13 via the line 139. The processor may reset the unplugged detection unit 13 with a signal output from the pin 4 of the processor 120 via the lead 137. After setting, a static check is made for connection. For this purpose, ground potential is queried via a line 192, which is present at the connection P4 of the interface 8 of the postal security module PSM 100 and can only be interrogated when the security module 100 is inserted correctly. When plugged security module 100 ground potential of the negative pole 104 of the battery 134 of the postal security module PSM 100 is placed on the port P23 of the interface 8 and is thus interrogated at port P4 of the interface 8 via the line 192 of the unplugged detection unit 13.

At the pins 6 and 7 of the processor 120 is a line loop, which is looped back to the processor 120 via the pins P1 and P2 of the contact group 102 of the interface 8. For dynamic testing of the connectedness of the postal security module PSM 100 to the motherboard 9, the processor 120 generates alternating signal levels at quite irregular time intervals at the pins 6, 7 and looping them back through the loop.

The postal security module PSM 100 is equipped with a long-live battery, which also allows monitoring of the use, without the security module is connected to a system voltage of a postal processing facility. Proper use, operation, installation or installation in the appropriate environment are those to be tested by the functional units of the safety module Properties. An initial installation is made by the manufacturer of the postal security module. Thus, after this initial installation, it is only necessary to check whether the postal security module is disconnected from its field of application (post-processing device), this usually taking place during an exchange.

The monitoring of this condition is performed by the unplugged detection unit 13. In this case, a voltage level is monitored via the ground connection at pin 4 of the interface unit 8. When replacing the functional unit, this ground connection is interrupted and the unplugged detection unit 13 registers this process as information. Since for each separation of the security module 100 from the interface unit 8, the storage of this information by the special battery-powered circuitry is ensured, an evaluation of this information can be done at any time, if a restart is desired. The regular evaluation of this unplugged signal on the line 139 of the unplugged detection unit 13 allows the processor 120 to delete sensitive data without, however, altering the accounting and customer data in the NVRAM memories. The current state of the postal security module with the deleted sensitive data can be understood as a maintenance condition, in which usually the replacement, repair or otherwise is made. Since the sensitive data of the functional unit are deleted, an error due to improper handling of the postal security module is excluded. The sensitive data are, for example, cryptographic keys. The processor 120 prevents in the maintenance state a core functionality of the postal security module, which consists for example in the billing and / or calculation of a security code for the security marking in a security print.

For recommissioning the postal security module PSM is first inserted and electrically connected to the corresponding interface unit 8 of a mail processing device. Then the device is switched on and thus the postal security module is again supplied with system voltage Us +. Due to the special condition, the proper installation of the postal security module must now be rechecked by its functional unit. For this purpose, a second stage of a test (dynamic plug-in detection) is provided. Via one between the first functional unit (processor 120) and the current loop 18 of the interface unit 8 made operative connection information is exchanged, the error-free transmission provides evidence of proper installation. This is a prerequisite for a successful restart.

For the state change to the normal operating state, a reinitialization of the sensitive data is now required. A communication is made between the postal security module and a third entity, the latter transmitting this sensitive data. Upon successful transmission, the untagged detection unit 13 is reset and the postal security module returns to its normal operating state. The restart is complete.

The FIG. 2 shows a block diagram of a postage meter, which is equipped with a chip card read / write unit 70 for reloading change data by chip card and with a printing device 2, which is controlled by a control device 1. The control device 1 has a motherboard 9 equipped with a microprocessor 91 with associated memories 92, 93, 94, 95.

The program memory 92 contains an operating program for at least printing and at least safety-related components of the program for a predetermined format change of a portion of the user data.
The RAM RAM 93 is used for volatile intermediate storage of intermediate results. NVM 94 non-volatile memory is used for non-volatile caching of data, such as statistical data organized by cost center. The calendar / clock module 95 also contains addressable but non-volatile memory areas for the non-volatile intermediate storage of intermediate results or also known program parts (for example for the DES algorithm). It is provided that the control device 1 is connected to the chip card write / read unit 70, wherein the microprocessor 91 of the control device 1 is programmed, for example, to load the payload N from the memory area of a chip card 49 for their application in corresponding memory areas of the franking machine , A first chip card 49 inserted in a slot 72 of the chip card write / read unit 70 allows reloading of a data record into the franking machine for at least one application. The smart card 49 contains, for example, the postage for all the usual postal carrier services according to the tariff of the postal authority and a post carrier code to generate a stamp image with the franking machine and to stamp the postal items according to the tariff of the postal authority.

The control device 1 forms the actual meter with the means 91 to 95 of the aforementioned motherboard 9 and also includes a keyboard 88, a display unit 89 and an application-specific circuit ASIC 90 and the interface 8 for the postal security module PSM 100. The security module PSM 100 is about a control bus to the aforementioned ASIC 90 and the microprocessor 91 and via the parallel μC bus at least with the means 91 to 95 of the motherboard 9 and connected to the display unit 89. The control bus carries lines for the signals CE, RD and WR between the security module PSM 100 and the aforementioned ASIC 90. The microprocessor 91 preferably has a pin for an output from the security module PSM 100 interrupt signal i, other connections for the keyboard 88, a For example, the serial interface SI-1 for the connection of the chip card read / write unit 70 and a serial interface SI-2 for the optional connection of a MODEM by means of the MODEM can be used to increase the credit stored in the non-volatile memory of the postal security device PSM 100.

The postal security device PSM 100 is surrounded by a secured housing. Before each franking imprint, a hardware settlement is carried out in the postal security module PSM 100. Billing is independent of cost centers. The postal security agent PSM 100 can be designed internally as in the European application EP 789 333 A3 was described in more detail.

It is contemplated that the ASIC 90 may include a serial interface circuit 98 to a post-stream powered device, a serial interface circuit 96 to the sensors and actuators of the printing device 2, a serial interface circuit 97 to the print control electronics 16 for the printhead 4, and a serial interface circuit 99 to one has the printing device 20 in the post-stream downstream device. Of the DE 197 11 997 a variant for the peripheral interface can be removed, which suitable for several peripheral devices (stations). It is entitled: Arrangement for communication between a base station and other stations of a mailing machine and their emergency shutdown.

The interface circuit 96 coupled to the machine base interface circuit 14 provides at least one connection to the sensors 6, 7, 17 and to the actuators, such as the drive motor 15 for the roller 11 and a cleaning and sealing station RDS 40 for the ink jet printhead 4 , as well as to the label dispenser 50 in the machine base. The basic arrangement and the interaction between the inkjet printhead 4 and the RDS 40 are the DE 197 26 642 C2 removable, entitled: Arrangement for positioning an ink jet printhead and a cleaning and sealing device.
One of the arranged in the guide plate 20 sensors 7, 17 is the sensor 17 and is used to prepare the pressure release during letter transport. The sensor 7 is used for initial letter recognition for the purpose of triggering the letter transport. The transport device consists of a conveyor belt 10 and two rollers 11,11 '. One of the rollers is equipped with a motor 15 drive roller 11, another is the follower tension roller 11 '. Preferably, the drive roller 11 is designed as a toothed roller, according to the conveyor belt 10 is designed as a toothed belt, which ensures the unambiguous power transmission. An encoder 5, 6 is coupled to one of the rollers 11, 11 '. Preferably, the drive roller 11 is firmly seated with an incremental encoder 5 on an axis. The incremental encoder 5 is designed for example as a slotted disk, which cooperates with a light barrier 6, and outputs via the line 19 an encoder signal to the motherboard 9 from.
It is envisaged that the individual printing elements of the print head are connected within its housing with a print head electronics and that the print head for a purely electronic pressure can be controlled. The pressure control is based on the path control, whereby the selected stamp offset is taken into account, which is entered by keyboard 88 or if necessary by chip card and stored in memory NVM 94 non-volatile. A planned imprint thus results from stamp offset (without printing), the franking print image and possibly further print images for advertising clichés, shipping information (optional prints) and additional editable messages. The nonvolatile memory NVM 94 has a plurality of memory areas. among them are those that non-volatile store the charged postage fee tables.
The smart card write / read unit 70 consists of an associated mechanical support for the microprocessor card and contact unit 74. The latter allows a secure mechanical support of the smart card in the read position and clear signaling of reaching the reading position of the smart card in the contacting unit. The microprocessor card with the microprocessor 75 has a programmed read capability for all types of memory cards or smart cards. The interface to the franking machine is a serial interface in accordance with the RS232 standard. The data transfer rate is min. 1.2 K baud. The power supply is switched on by means of a switch 71 connected to the mainboard. After the power supply has been switched on, a self-test function with a ready message takes place.

In the FIG. 3 is a perspective view of the postage meter from behind. The franking machine consists of a meter 1 and a base 2. The latter is equipped with a smart card write / read unit 70, which is arranged behind the guide plate 20 and accessible from the housing upper edge 22. After switching on the franking machine by means of the switch 71, a chip card 49 is inserted from top to bottom in the insertion slot 72. A supplied standing on the edge letter 3, which rests with its surface to be printed on the guide plate is then printed according to the input data with a franking stamp 31. The letter feeding opening is bounded laterally by a transparent plate 21 and the guide plate 20. The status display of the security module 100 inserted on the motherboard 9 of the meter 1 is visible from the outside through an opening 109.

The FIG. 4 shows a block diagram of the postal security module PSM 100 in a preferred variant. The negative pole of the battery 134 is connected to ground and a pin P23 of the contact group 102. The positive pole of the battery 134 is connected to the one input of the voltage changeover switch 180 via the line 193, and the system voltage leading line 191 is connected to the other input of the voltage changeover switch 180. As battery 134 is the type SL-389 / P for a lifetime up to 3.5 years or the type SL-386 / P for a lifetime up to 6 years with a maximum power consumption by the PSM 100 is suitable as a voltage switch 180, a commercial circuit of the type ADM 8693ARN be used. The output of the voltage changeover switch 180 is connected via the line 136 to the battery monitoring unit 12 and the detection unit 13. The battery monitoring unit 12 and the detection unit 13 communicate with the pins 1, 2, 4 and 5 of the processor 120 via the lines 135, 164 and 137, 139 in communication. The output of the voltage changeover switch 180 is also connected via the line 136 to the supply input of a first memory SRAM, which becomes the non-volatile memory NVRAM of the first technology by the existing battery 134.
The security module communicates with the postage meter via the system bus 115, 117, 118. The processor 120 may communicate via the system bus and a modem 83 in communication with a remote data center. The billing is performed by the ASIC 150 and checked by the processor 120. The postal billing data is stored in non-volatile memory of different technology.
The system voltage is applied to the supply input of a second memory NV-RAM 114. The latter is a non-volatile memory NVRAM of a second technology, (SHADOW-RAM). This second technology preferably comprises a RAM and an EEPROM, the latter automatically assuming the data contents in the event of system voltage failure. The NVRAM 114 of the second technology is connected to the corresponding address and data inputs of the ASIC 150 via an internal address and data bus 112, 113.

The ASIC 150 contains at least one hardware abort unit for the calculation of the postal data to be stored. Programmable Array Logic (PAL) 160 accommodates access logic to ASIC 150. The ASIC 150 is controlled by the PAL 160 logic. An address and control bus 117, 115 from the motherboard 9 is connected to corresponding pins of the PAL 160 logic and the PAL 160 generates at least a control signal for the ASIC 150 and a control signal 119 for the program memory FLASH 128. The processor 120 executes a program stored in the FLASH 128. Processor 120, FLASH 28, ASIC 150, and PAL 160 are interconnected via a module-internal system bus that includes lines 110, 11, 12, 126, 119 for data, address, and control signals.

The processor 120 of the security module 100 is connected via a module-internal data bus 126 to a FLASH 128 and to the ASIC 150. The FLASH 128 is supplied with system voltage Us +. For example, it is a 128 Kbyte FLASH memory type AM29F010-45EC. The ASIC 150 of the postal security module 100 supplies addresses 0 to 7 to the corresponding address inputs of the FLASH 128 via a module-internal address bus 110. The processor 120 of the security module 100 delivers the addresses 8 to 15 to the corresponding address inputs of the FLASH 128 via an internal address bus 111 The ASIC 150 of the security module 100 is connected via the contact group 101 of the interface 8 to the data bus 118, to the address bus 117 and to the control bus 115 of the motherboard 9 in communication connection.

It is envisaged that the processor 120 has memory 122, 124 to which an operating voltage Ub + from a voltage monitoring unit 12 is supplied via the line 138. In particular, a real-time clock RTC 122 and the memory RAM 124 are supplied by an operating voltage via the line 138. The voltage monitor unit (Battery Observer) 12 also provides a status signal 164 and responds to a control signal 135. The voltage selector 180, as output voltage on the line 136 for the battery observer 12 and memory 116, passes that of its input voltages as a supply voltage which is higher than the other one , Due to the possibility of automatically feeding the described circuit as a function of the magnitude of the voltages Us + and Ub + with the larger of the two, during normal operation the battery 134 can be exchanged without loss of data.

The battery 134 of the security module 100 feeds in the rest periods outside normal operation in the aforementioned manner the real-time clock (RTC) 122 with date and / or time registers and / or the static RAM (SRAM) 124, which holds security-relevant data. If the voltage of the battery drops below a certain limit during battery operation, the voltage monitoring unit 12 connects the feed point for the RTC and SRAM to ground until reset. The voltage at the RTC and SRAM is then at 0V. As a result, the SRAM 124, which contains eg important cryptographic keys, is deleted very quickly. At the same time also the registers the RTC 122 is cleared and the current time and date are lost. This action prevents a potential attacker from stopping the postage meter internal clock 122 by manipulating the battery voltage without losing any security related data. This prevents the attacker from bypassing security measures such as long-time watchdogs.

The RESET unit 130 is connected via the line 131 to the pin 3 of the processor 120 and to a pin of the ASIC 150. The processor 120 and the ASIC 150 are reset by a reset generation in the RESET unit 130 when the supply voltage drops.

Simultaneously with the indication of the undervoltage of the battery, the described circuit changes into a self-holding state in which it remains even when subsequently increasing the voltage. The next time the module is switched on, the processor can query the state of the circuit (status signal) and thus and / or via the evaluation of the contents of the erased memory, conclude that the battery voltage has in the meantime fallen below a certain value. The processor may reset the monitor circuit, i. "make sharp.

The unplugged detection unit 13 has to measure the input voltage line 192, which is connected via the plug of the security module and interface 8, preferably via a socket on the motherboard 9 of the postage meter to ground. This measurement is used for static monitoring of the arrangement and forms the basis for monitoring at a first stage. It is contemplated that the unplugged detection unit 13 comprises resettable latching means, the latching being triggered when the voltage level on a sense voltage line 192 deviates from a predetermined potential. At the same time, the evaluation logic includes the processor 120 connected to the other functional units, which is programmed to detect and change the respective state of the security module 100. The state of latching can be queried via the line 139 from the processor 120 of the security module 100. The measuring voltage potential on the Line 192 corresponds to ground potential if security module 100 is properly inserted. On line 139 is operating voltage potential. Ground voltage potential is present on the line 139 when the security module 100 is unplugged. The processor 120 has a fifth pin 5, to which the line 139 is connected in order to query the state of the unplugged detection unit 13, whether it is switched to ground potential with latching. In order to reset the state of latching of the unplugged detection unit 13 via the line 137, the processor 120 has a fourth pin 4.

Furthermore, a current loop 18 is provided which also connects the pins 6 and 7 of the processor 120 via the plug of the security module and via the socket on the motherboard 9 of the postage meter machine. The lines on the pins 6 and 7 of the processor 120 are closed only to a current loop 18 at a plugged into the motherboard 9 PSM 100. This loop forms the basis for a dynamic monitoring of the plugged-in safety module on a second level.

The processor 120 internally has a processing unit CPU 121, a real time clock RTC 122, a RAM unit 124, and an input / output unit 125. The processor 120 is equipped with pins 8, 9 for outputting at least one signal for signaling the state of the security module 100. At the pins 8 and 9 are I / O ports of the input / output unit 125 to which module-internal signaling means are connected, for example, colored light emitting diode LED's 107, 108, which signal the state of the security module 100. The safety modules can assume different states in their life cycle. So, for example, to detect whether the module contains valid cryptographic keys. Furthermore, it is also important to distinguish whether the module is working or is defective. The exact type and number of module states depends on the implemented functions in the module and on the implementation.

Based on FIG. 5 the circuit diagram of the detection unit 13 will be explained. It is envisaged that the unplugged detection unit 13 comprises a voltage divider consisting of a series circuit of resistors 1310, 1312, 1314 and is placed between a tapped by a capacitor 1371 supply voltage potential and a Meßspannungspotential on the line 192. The circuit is supplied via line 136 with the system or battery voltage. The respective supply voltage from the line 136 passes through a diode 1369 to the capacitor 1371 of the circuit. On the output side of the circuit is an inverter 1320, 1398. In the normal state, the transistor 1320 of the inverter is disabled and the supply voltage is effective via the resistor 1398 on the line 139, which therefore logic '1', ie H level in the normal state. An L level on line 139 is advantageous as a status signal for unplug because then no current flows into pin 5 of processor 120, increasing battery life. The diode 1369, preferably in conjunction with an electrolytic capacitor 1371, ensures that the circuit upstream of the inverter is supplied with a voltage over a relatively long period of time (> 2 sec), in which its function is ensured, even though the voltage on the line 136 is already high was turned off.
The voltage divider 1310, 1312, 1314 has a tap 1304 to which a capacitor 1306 and the noninverting input of a comparator 1300 are connected. The inverting input of the comparator 1300 is connected to a reference voltage source 1302. The output of the comparator 1300 is connected on the one hand via the negator 1324.1398 to the line 139 and on the other hand to the control input of a switching means 1322 for latching. The switching means 1322 is connected in parallel with the resistor 1310 of the voltage divider, and the latching switching means 1316 is connected between the tap 1304 and ground. The tap 1304 of the voltage divider is at the junction of the resistors 1312 and 1314. The capacitor 1306 connected between the tap 1304 and ground prevents vibrations. The voltage at tap 1304 of the voltage divider is compared in comparator 1300 with the reference voltage of source 1302. If the voltage to be compared at tap 1304 is less than the reference voltage of source 1302, then the comparator output remains at L level and transistor 1320 of the inverter is disabled. As a result, the line 139 now receives operating voltage potential and the status signal leads logically '1'. The voltage divider is dimensioned so that at ground potential on the line 192, the tap 1304 carries a voltage which safely below the switching threshold of the comparator 1300 is located. If the connection is interrupted and the line 192 is no longer connected to ground, because the security module 100 has been detached from the socket on the motherboard 9 or interface unit 8 of the franking machine, the voltage at the tap 1304 is pulled over the voltage of the reference voltage source 1302 and the Comparator 1300 switches over. The comparator output is switched to H level, and thus the transistor 1320 is turned on. As a result, the line 139 is connected to ground potential and the status signal logic '0.
By means of a transistor 1322, which is connected in parallel with the resistor 1310 of the voltage divider, a self-holding circuit of the unplugged detection unit 13 is realized. The control input of transistor 1322 is switched to the H level by the comparator output. As a result, the transistor 1322 turns on and bridges the resistor 1310. As a result, the voltage divider is formed only by the resistors 1312 and 1314. As a result, the switching threshold is increased so much that the comparator remains in the switched state when the line 192 again ground potential, because the security module was plugged again.
The state of the circuit can be queried via the signal on line 139 from the processor 120.
It is contemplated that the unplugged detection unit 13 as circuit means comprises a line 137 and a latching resetting means 1316, the reset being triggerable by the processor 120 via a signal on the line 137.
The processor 120 can at any time via a user circuit ASIC 150, via a first contact group 101, via a system bus of the controller 1 and for example via the microprocessor 91 via modem 83 to contact a remote data center, which checks the billing data and optionally other data to the Processor 120 transmitted. The user circuit ASIC 150 of the security module 100 is connected to the processor 120 via a module-internal data bus 126.
The processor 120 may reset the untagged detection unit if reinitialization could be successfully completed using the transmitted data. For this purpose, the transistor 1316 is switched through via the reset signal on the line 137 and thus the voltage at the tap 1304 below the reference voltage of Source 1302 and disable transistors 1320 and 1322. When transistor 1322 is normally off, resistors 1310 and 1312 in series form the upper part of the above voltage divider and the switching threshold is lowered back to the original state.

The FIG. 6 shows the mechanical structure of the safety module in side view. The security module is designed as a multi-chip module, that is, a plurality of functional units are interconnected on a printed circuit board 106. The security module 100 is potted with a hard potting compound 105, wherein the battery 134 of the security module 100 is arranged outside of the potting compound 105 on a printed circuit board 106 interchangeable. For example, it is potted with a potting material 105 that signal means 107, 108 protrude from the potting material at a first location and that the circuit board 106 protrudes laterally with the inserted battery 134 a second location. The printed circuit board 106 also has battery contact terminals 103 and 104 for connecting the poles of the battery 134, preferably on the component side above the printed circuit board 106. It is envisaged that for plugging the postal security module PSM 100 on the main board of the meter 1, the contact groups 101 and 102nd are arranged below the circuit board 106 (trace side) of the security module 100. The user circuit ASIC 150 is via the first contact group 101 - in a manner not shown - in communication with the system bus of a control device 1 and the second contact group 102 serves to supply the security module 100 with the system voltage. If the security module is plugged onto the motherboard, then it is preferably arranged within the meter housing in such a way that the signal means 107, 108 near an opening 109 or projects into this. The meter housing is thus advantageously designed so that the user can still see the status of the security module from the outside. The two light emitting diodes 107 and 108 of the signal means are controlled via two output signals of the I / O ports to the pin 8, 9 of the processor 120. Both LEDs are housed in a common component housing (Bicolorleuchtdiode), which is why the dimensions or the diameter of the opening can remain relatively small and is of the order of the signal means. In principle, three different colors can be displayed (red, green, orange), of which only two are used (red and orange) green). To distinguish the state, the LEDs are also used flashing, so that 5 different state groups can be distinguished, which are characterized by the following LED states: LED off, red LED flashing, red LED, green flashing LED, green LED.

In the FIG. 7 is a plan view of the postal security module shown.

The FIGS. 8a or 8b show a view of the security module respectively from the right and from the left. The location of the contact groups 101 and 102 below the printed circuit board 106 is from the FIGS. 8a and 8b combined with FIG. 6 clear.

According to the invention, the postal device, in particular a franking machine, however, the security module can also have a different design, which makes it possible, for example, it can be plugged onto the motherboard of a personal computer, which drives a commercial printer as a PC meter.

Claims (12)

1. A method for the protection of a security module comprising the following steps:

   ■ Monitoring of the proper installation of the security module (100) by means of a first (120), a second (12) and a third functional unit (13);

   ■ Deletion of sensitive data in the security module as a consequence of an improper utilization or exchange of the security module (100) by means of at least the second functional unit (12);

   ■ Blocking of the functionality of the security module (100) by means of the third functional unit (13) during an exchange of the security module (100);

   ■ Re-initialization of the security module (100) by means of the first functional unit (120) with sensitive data that were deleted after an improper utilization or exchange of the security module (100);

   ■ Restarting of the security module (100) by release of the second (12) and third functional units (13) of the security module (100).
2. A method according to Claim 1, characterized in that the re-initialization is effected, in combination with a communication with a remote data central, by the first functional unit, after a dynamic detection whether the security module (100) is plugged-in was successfully completed, wherein, during the detection, data are exchanged via an operational connection established between the first functional unit (120) and a current loop (18) of an interface unit (8), the error-free transmission of which provides proof of the proper installation of the security module (100), and that the release of the second (12) and third functional units (13) of the security module is effected by resetting them, wherein the first functional unit is a processor (120), the second functional unit is a voltage supervision unit (12) with resettable locking and the third functional unit is a non-plugged-in detection circuit (13) with resettable locking.
3. An arrangement for performing the method according to Claim 1 with a security module that is equipped with a logic (120, 150, 160), with sensors with a battery (134), with means for supply with a system voltage and with a voltage change-over switch (180) that is connected via a first line (136) with a second functional unit (12) designed as a voltage supervision unit that delivers, via a second line (138), an operating voltage to a memory (122, 124),
   characterized in that a third functional unit (13) designed as a non-plugged-in detection circuit is provided with circuit means (1310, 1316, 1322, 1324) for a resettable locking, wherein said locking is triggered when the voltage level on a fourth measuring voltage line (192) deviates from a pre-defined potential, and that the logic comprises a first functional unit (120) designed as a processor that is connected with the other functional units and is programmed for determining and changing the respective status of the security module (100).
4. An arrangement according to Claim 3, characterized in that the non-plugged-in detection circuit (13) is provided with a third line (137) and a switching means (1316) as circuit means for resetting the locking, wherein said locking can be triggered by the processor (120) by a signal on the third line (137).
5. An arrangement according to Claims 3 and 4, characterized in that the non-plugged-in detection circuit (13) is provided with a voltage divider formed by resistors connected in series (1310, 1312, 1314) and is connected between a supply voltage potential pickable by a capacitor (1371) and a measuring voltage potential on a fourth line (192), wherein the supply voltage gets from the first line (136) via a diode (1369) to the capacitor (1371; that the voltage divider (1310, 1312, 1314) has a tapping (1304) to which a capacitor (1306) and the non-inverting input of a comparator (1300) are connected; that the inverting input of a comparator (1300) is connected to a reference voltage source (1302); that the output of the comparator (1300) is connected, on the one hand, via a negator (1324, 1398), to a fifth line (139) and, on the other hand, to the control input of a switching means (1322) for the locking, said switching means (1322) being connected in parallel to the resistor (1310) of the voltage divider, and that the switching means (1316) for resetting the locking is connected between the tapping (1304) and earth.
6. An arrangement according to Claim 5, characterized in that the status of the locking can be inquired by the processor (120) of the security module (100) via the fifth line (139).
7. An arrangement according to Claim 6, characterized in that the measuring voltage potential on the fourth line (192) corresponds to the earth potential and the voltage potential on the fifth line (139) corresponds to the operating voltage potential when the security module (100) is properly plugged in and that otherwise earth potential is on the fifth line (139) when the security module (100) is unplugged.
8. An arrangement according to Claims 3 to 7, characterized in that the processor (120) is provided with memory means (122, 124) to which an operating voltage Ub+ is led from a voltage supervision unit (12) via the second line (138); that the processor (120) is supplied with system voltage Us+ and has a fourth pin (Pin 4) in order to reset the status of locking of the non-plugged-in detection circuit (13) via the third line (137) as well as a fifth pin (Pin 5) to which the fifth line (139) is connected in order to inquire the status of the non-plugged-in detection circuit (13).
9. An arrangement according to Claim 8, characterized in that the security module (100) is provided with a user circuit ASIC (150) and that the processor (120) is connected, via an internal data bus (126) of the module, with the user circuit ASIC (150), wherein the latter is in a communication connection with the system bus of a control device (1) via a first terminal group (101).
10. An arrangement according to one of Claims 3 to 9, characterized in that the security module (100) is enclosed by a hard sealing compound (105); that the battery (134) of the security module (100) is arranged replaceably outside the sealing compound (105) on a printed circuit board (106); that the printed circuit board (106) contains the battery contact clamps (103 and 104) for connecting the poles of the battery (134) and a second terminal group (102) for the supply of the security module (100) with system voltage; and that at least one of the terminal groups (101, 102) is designed for the static and dynamic supervision of the plugged-in status of the security module (100).
11. An arrangement according to Claim 10, characterized in that the processor (120) has pins (Pins 6, 7) for the dynamic supervision of the plugged-in status of the security module, to which lines are connected that are connected in a current loop (18) when the security module (100) was plugged in.
12. An arrangement according to one of Claims 3 to 11, characterized in that the processor (120) of the first functional unit (100) is provided with pins (Pins 8, 9) for the output of at least one signal for signalling the status of the security module (100).

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