DE102014214823A1 - Determination of a delay - Google Patents

Abstract

For example, a method for determining a delay is proposed in which a first component (101) of a second component (102) provides a first message (104) comprising a first identifier (ch1), wherein the second component (102) of the first Component (101) provides a second message (105) comprising a second identifier (ch2), in which the second component (102) of the first component (101) comprises a third message (107) comprising first time information (T2; t2, t3) based on a time of receipt (t2) of the first message (104) and a transmission time (t3) of the second message (105) together with a first coded value (M1), the first coded value on the first time information (T2; t2, t3), wherein the first component (101) determines the delay (VZ) based on a transmission time (t1) of the first message, a reception time (t4) of the second message and the first time information (T2; t2, t3) and the the first component (101) outputs the first time information (T2; t2, t3) is checked on the basis of the first coded value (M1).

Description

The invention relates to a method for determining a delay, a vehicle and corresponding devices or components that are connected to each other via a (communication) network.

Systems for time synchronization, eg NTP, PTP, IEEE 802.1X or systems derived from them are often neither secured with regard to safety requirements against technical faults nor with regard to security requirements against malicious manipulation.

A vehicle (e.g., passenger cars, trucks, and / or motorcycles) typically includes a network, e.g. at least one bus system, for exchanging information between control units of the vehicle. The network can be or include an Ethernet. The information may be any data, e.g. User data, control data or control data act.

The controllers may be arranged in the vehicle so that they are relatively easily accessible to an attacker. The attacker can influence the network via the control unit or any connection of the network:
For example, the controller may be removed and replaced with a manipulated device. Also, a variety of intervening attacks ("man-in-the-middle" attacks) are possible. The attacker stands either physically or logically between two (or more) communication partners and has with his system control over the traffic between two or more network participants and can view and manipulate the information as desired. Here, the attacker deceives the communication partners to be the respective counterpart (cf., eg http://de.wikipedia.org/wiki/Man-in-the-Middle-Angriff ).

The present document therefore addresses the technical problem of designing access to an Ethernet network of a vehicle in a cost-efficient manner to avoid unauthorized access (including through a man-in-the-middle attack) can.

A message authentication code (MAC) is also known, which is used to obtain certainty about the origin of data or messages and to verify their integrity. A MAC algorithm for creating a MAC requires as input parameters the data to be protected as well as a secret key (see also eg http://de.wikipedia.org/wiki/Message_Authentication_Code ).

In order to use systems for time synchronization as a basis for the function of critical vehicle functions, however, a backup with regard to safety (technical errors) or security (malicious manipulation) is necessary.

The object of the invention is to avoid the disadvantages mentioned above and in particular to provide an efficient solution for securing a time synchronization against attacks.

This object is achieved according to the features of the independent claims. Further developments of the invention will become apparent from the dependent claims.

• – bei dem eine erste Komponente einer zweiten Komponente eine erste Nachricht umfassend eine erste Kennung bereitstellt,
• – bei dem die zweite Komponente der ersten Komponente eine zweite Nachricht umfassend eine zweite Kennung bereitstellt,
• – bei dem die zweite Komponente der ersten Komponente eine dritte Nachricht umfassend eine erste Zeitinformation basierend auf einer Empfangszeit der ersten Nachricht und einer Sendezeit der zweiten Nachricht zusammen mit einem ersten codierten Wert bereitstellt, wobei der erste codierte Wert auf der ersten Zeitinformation basiert,
• – bei dem die erste Komponente die Verzögerung ermittelt basierend auf einer Sendezeit der ersten Nachricht, einer Empfangszeit der zweiten Nachricht und der ersten Zeitinformation und
• – bei dem die erste Komponente die erste Zeitinformation anhand des ersten codierten Werts überprüft.

To solve the problem, a method for determining a delay is given,

• In which a first component of a second component provides a first message comprising a first identifier,
• In which the second component of the first component provides a second message comprising a second identifier,
• - wherein the second component of the first component provides a third message comprising first time information based on a time of reception of the first message and a time of transmission of the second message together with a first encoded value, the first encoded value based on the first time information,
• Wherein the first component determines the delay based on a transmission time of the first message, a reception time of the second message and the first time information, and
• - In which the first component checks the first time information based on the first coded value.

The checking comprises in particular a check of a validity and / or authenticity. The enumeration of the above steps does not dictate a mandatory order. For example, the check may be made before, after or simultaneously with the determination of the delay.

It should be noted that the check may include a check as to whether the data obtained are correct and whether they are from the source provided, ie are authentic.

The first time information may include, for example, the reception time of the first message and the transmission time of the second message, or a difference between both times.

A further development is that the first encoded value is additionally based on the first identifier and on the second identifier.

The identifiers can be used to ensure that the messages are only valid for a limited time. If the identifier contains time information, e.g. a predetermined fixed period of time are added, from which this message is then no longer valid. Alternatively, a sequence of validity can be coded into the identifier. The identifier may in particular include a combination of an identification and a time information. Also, the identifier itself can be encrypted or determined by means of a (cryptographic) one-way or hash function.

Providing the message may e.g. by transmitting the message or the message can be stored in shared memory (e.g., shared memory). In this case, the addressee retrieves the message from the memory; the addressee can regularly check the memory for new messages or be informed that there are messages for him. Thus, providing includes both the active transmission of the transmitter to the receiver (push mechanism) and a mechanism in which the receiver picks up the messages (pull mechanism).

• – einer Hashfunktion;
• – einer kryptographischen Hashfunktion;
• – einer Einwegfunktion;
• – einem MAC-Algorithmus;
• – einer symmetrischen Verschlüsselung;
• – einer asymmetrischen Verschlüsselung;
• – einer asymmetrischen Signatur.

Another development is that the first coded value is determined by means of at least one of the following functions:

• - a hash function;
• A cryptographic hash function;
• - a one-way function;
• A MAC algorithm;
• - a symmetric encryption;
• - asymmetric encryption;
• - an asymmetric signature.

• – einer Identifikation der erstellenden Netzwerkkomponente;
• – einer Identifikation mindestens einer Netzwerkkomponente;
• – einer Datumsinformation umfassend z.B. mindestens eine der folgenden Informationen: Tag, Monat, Jahr, Uhrzeit, Stunde, Minute, Sekunde;
• – einer Zufallszahl;
• – einer im System eindeutigen Zahl;
• – einer Gültigkeitsinformation.

In particular, it is a development that the first identifier is determined by the first component based on one of the following information or values:

• - an identification of the creating network component;
• An identification of at least one network component;
• A date information comprising eg at least one of the following information: day, month, year, time, hour, minute, second;
• - a random number;
• - a number unique in the system;
• - a validity information.

• – einer Identifikation der erstellenden Netzwerkkomponente;
• – einer Identifikation mindestens einer Netzwerkkomponente;
• – einer Datumsinformation umfassend z.B. mindestens eine der folgenden Informationen: Tag, Monat, Jahr, Uhrzeit, Stunde, Minute, Sekunde;
• – einer Zufallszahl;
• – einer im System eindeutigen Zahl;
• – einer Gültigkeitsinformation.

It is also a development that the second identifier is determined by the second component based on one of the following information or values:

• - an identification of the creating network component;
• An identification of at least one network component;
• A date information comprising eg at least one of the following information: day, month, year, time, hour, minute, second;
• - a random number;
• - a number unique in the system;
• - a validity information.

Further, it is a further development that the first component of the second component provides a fourth message, the fourth message comprising the delay and a second encoded value, the second encoded value based on the delay.

• – einer Hashfunktion;
• – einer kryptographischen Hashfunktion;
• – einer Einwegfunktion;
• – einem MAC-Algorithmus;
• – einer symmetrischen Verschlüsselung;
• – einer asymmetrischen Verschlüsselung;
• – einer asymmetrischen Signatur.

In the context of an additional development, the second encoded value is determined by means of at least one of the following functions:

• - a hash function;
• A cryptographic hash function;
• - a one-way function;
• A MAC algorithm;
• - a symmetric encryption;
• - asymmetric encryption;
• - an asymmetric signature.

A next development is that the fourth message of the second component is provided if the verification of the first time information was successful.

An embodiment is that the fourth message additionally comprises the transmission time of the first message and in which the second encoded value is additionally based on the transmission time of the first message.

An alternative embodiment is that the second component checks the delay and the transmission time of the first message based on the second encoded value, and if the check was successful, a system time of the second component based on the transmission time of the first message and / or the delay will be changed.

For example, the system time is an absolute or relative clock that is provided by the approach suggested here. In particular, the clocks of the components involved are synchronized with each other.

A next embodiment is that the change of the system time of the second component at predetermined times, in particular regularly or irregularly, is performed.

It is also an embodiment that the system time of the second component is not changed if the check based on the second encoded value was unsuccessful.

A development consists in that the first component and the second component are coupled to one another via a network, in particular a bus system or the Ethernet.

An additional embodiment is that the first component and the second component are control devices of a vehicle.

Another embodiment is that the first component is a time synchronization master and the second component is a client.

It is also a possibility that the first component and / or the second component comprise a hardware and / or software component.

• – bei dem die erste Komponente der zweiten Komponente eine erste Nachricht umfassend eine erste Kennung bereitstellt,
• – bei dem die zweite Komponente der ersten Komponente eine zweite Nachricht umfassend eine zweite Kennung bereitstellt,
• – bei dem die zweite Komponente der ersten Komponente eine dritte Nachricht umfassend eine erste Zeitinformation basierend auf einer Empfangszeit der ersten Nachricht und einer Sendezeit der zweiten Nachricht zusammen mit einem ersten codierten Wert bereitstellt, wobei der erste codierte Wert auf der ersten Zeitinformation basiert,
• – bei dem die erste Komponente eine Verzögerung ermittelt basierend auf einer Sendezeit der ersten Nachricht, einer Empfangszeit der zweiten Nachricht und der ersten Zeitinformation und
• – bei dem die erste Komponente die erste Zeitinformation anhand des ersten codierten Werts überprüft.

The above object is also achieved by means of a vehicle having a first component and a second component,

• In which the first component of the second component provides a first message comprising a first identifier,
• In which the second component of the first component provides a second message comprising a second identifier,
• - wherein the second component of the first component provides a third message comprising first time information based on a time of reception of the first message and a time of transmission of the second message together with a first encoded value, the first encoded value based on the first time information,
• Wherein the first component determines a delay based on a transmission time of the first message, a reception time of the second message and the first time information, and
• - In which the first component checks the first time information based on the first coded value.

• – einer Client-Komponente eine erste Nachricht umfassend eine erste Kennung bereitgestellt wird,
• – von der Client-Komponente eine zweite Nachricht umfassend eine zweite Kennung empfangen wird,
• – von der Client-Komponente eine dritte Nachricht umfassend eine erste Zeitinformation basierend auf einer Empfangszeit der ersten Nachricht und einer Sendezeit der zweiten Nachricht zusammen mit einem ersten codierten Wert empfangen wird, wobei der erste codierte Wert auf der ersten Zeitinformation basiert,
• – eine Verzögerung ermittelt wird basierend auf einer Sendezeit der ersten Nachricht, einer Empfangszeit der zweiten Nachricht und der ersten Zeitinformation, wobei die erste Zeitinformation anhand des ersten codierten Werts überprüft wird.

The object is also achieved by means of a master component which is set up in such a way that

• A client component is provided with a first message comprising a first identifier,
• A second message comprising a second identifier is received by the client component,
• Receiving from the client component a third message comprising a first time information based on a reception time of the first message and a transmission time of the second message together with a first encoded value, the first encoded value being based on the first time information,
• A delay is determined based on a transmission time of the first message, a reception time of the second message and the first time information, wherein the first time information is checked based on the first encoded value.

• – von einer Master-Komponente eine erste Nachricht umfassend eine erste Kennung empfangen wird,
• – der Master-Komponente eine zweite Nachricht umfassend eine zweite Kennung bereitgestellt wird,
• – der Master-Komponente eine dritte Nachricht umfassend eine erste Zeitinformation basierend auf einer Empfangszeit der ersten Nachricht und einer Sendezeit der zweiten Nachricht zusammen mit einem ersten codierten Wert bereitgestellt wird, wobei der erste codierte Wert auf der ersten Zeitinformation basiert,
• – so dass von der Master-Komponente eine Verzögerung ermittelbar ist basierend auf einer Sendezeit der ersten Nachricht, einer Empfangszeit der zweiten Nachricht und der ersten Zeitinformation, wobei von der Master-Komponente die erste Zeitinformation anhand des ersten codierten Werts überprüft wird.

Furthermore, the object is achieved by means of a client component which is set up such that

• A master component receives a first message comprising a first identifier,
• The master component is provided with a second message comprising a second identifier,
• The master component is provided with a first message containing first time information based on a time of reception of the first message and a time of transmission of the second message together with a first encoded value, the first encoded value based on the first time information,
• A delay can be determined by the master component based on a transmission time of the first message, a reception time of the second message and the first time information, wherein the master component checks the first time information based on the first encoded value.

It should be understood that the methods, devices and systems described herein may be used alone as well as in combination with other methods, devices and systems described in this document. Also, any aspects of the methods, devices, and systems described herein may be combined in a variety of ways. In particular, the features of the claims can be combined differently with each other.

Embodiments of the invention are illustrated and explained below with reference to the drawing.

It shows:

1 a flowchart for determining a delay time and for setting, in particular synchronization, a system time, in particular safety and security aspects are taken into account.

By way of example, a communication between two communication partners is described, which are connected to one another via a network, for example an Ethernet of a vehicle, and messages can exchange. In a system for time synchronization, a first communication partner is referred to as a master and a second communication partner as a client. A large number of clients can communicate with one master.

The communication partners are, for example, control units of a vehicle which are interconnected via the network (e.g., a bus system). Also, the communication partner may be a logical functionality (in) of a hardware device that may exchange messages with at least one other logical functionality or hardware device.

1 shows an exemplary diagram illustrating a message exchange between a master 101 and a client 102 for setting a system time.

Based on the in 1 As shown, the client can 102 the system time in the vehicle with the master 101 synchronize while maintaining security requirements. In particular, the approach presented here can significantly reduce the risk of a successful man-in-the-middle attack.

Preferably, the synchronization shown once or several times, if necessary, regularly at predetermined times, performed to a divergence of the system times of the master 101 and clients 102 counteract.

By means of a message 103 ("Time synchronization request") requests the client 102 a time synchronization from the master 101 at.

The master 101 receives the message 103 and answers with a message 104 ("Initialization of synchronization"). These news 104 contains an identifier ch1. Furthermore, the master measures and stores 101 a time t1 of sending the message 104 , It should be noted that the time t1 from the master 101 For example, it is first determined after the message 104 was sent.

The client 102 receives the message 104 Measures and stores a time t2 of reception and transmits a message 105 ("Synchronization delay request") together with an identifier ch2 to the master 101 , Furthermore, the client measures and stores 102 a time t3 of sending the message 105 , It should be noted that the time t3 from the client 102 For example, it is first determined after the message 105 was sent.

The client 102 determined in one step 106 a time delay T2 between receiving the message 104 and sending the message 105 according to T2 = t3 - t2.

• – die Zeitverzögerung T2,
• – einen MAC M1 basierend auf der Zeitverzögerung T2, der ersten Kennung ch1 und der zweiten Kennung ch2, d.h. M1 (T2, ch1, ch2).

The client continues to transmit 102 a message 107 ("Follow-up synchronization delay request") to the master 101 , The message 107 includes

• The time delay T2,
• A MAC M1 based on the time delay T2, the first identifier ch1 and the second identifier ch2, ie M1 (T2, ch1, ch2).

For example, to create a MAC, a (secret) key is used, which is the master 101 and the client 102 is known. Without this key, it is not possible (or very likely) for an attacker to generate the value M1. On the other hand, the master 101 verified the value M1 by generating a MAC with its key and the parameters T1, ch1 and ch2 known to it. If the MAC thus generated matches the value M1, the master can 101 with high probability assume that the time delay T2 from the client 102 and not from an attacker.

The master 101 receives the message 105 , Furthermore, the master measures and stores 101 a time t4 of receiving the message 105 ,

In one step 109 the master determines 101 a time delay T1 between sending the message 104 and receiving the message 105 determine according to T1 = t4 - t1.

Furthermore, the master 101 determine a delay VZ of the communication comprising transmitting and receiving direction according to VZ = T1 - T2.

• – die Verzögerung VZ,
• – die Zeit t1,
• – einen MAC M2 basierend auf der Verzögerung VZ und der Zeit t1, d.h. M2(VZ, t1).

The master 101 sends a message 108 ("Delay verification") to the client 102 , The message 108 includes

• The delay VZ,
• The time t1,
• A MAC M2 based on the delay VZ and the time t1, ie M2 (VZ, t1).

The client 102 receives the message 108 and can check the authenticity of the delay VZ and the time t1 based on the MAC M2. If it turns out that the MAC M2 could be checked successfully, it will be in one step 110 one Time counter that maps a system time, within the client 102 set based on the time t1. Optionally, this time counter can be corrected by means of the delay VZ, for example by a value VZ / 2.

Depending on an accuracy of the time base of the client 102 and depending on accuracy requirements and the determined delay VZ, the synchronization of the system time can be triggered again. In particular, it is possible that this synchronization of the system time is started regularly or irregularly.

It should be noted that other cryptographic functions, one-way functions, hash functions, etc. may be used instead of the MAC function. In particular, a common secret between each two network components or between multiple network components can be used for encryption. Alternatively, it is possible to use asymmetric encryption in which one key pair per network component enables both encryption and authentication.

• – einer Identifikation der erstellenden Netzwerkkomponente;
• – einer Identifikation mindestens einer Netzwerkkomponente;
• – einer Datumsinformation umfassend z.B. mindestens eine der folgenden Informationen: Tag, Monat, Jahr, Uhrzeit, Stunde, Minute, Sekunde;
• – einer Zufallszahl;
• – einer im System eindeutigen Zahl;
• – eine Gültigkeitsinformation.

The identifier ch1 may be an individual value determined by the master based on at least one predetermined criterion. For example, the identifier ch1 can be determined based on one of the following information or values:

• - an identification of the creating network component;
• An identification of at least one network component;
• A date information comprising eg at least one of the following information: day, month, year, time, hour, minute, second;
• - a random number;
• - a number unique in the system;
• - a validity information.

The same applies to the identifier ch2, by the client 102 is determined.

On the basis of the identifiers, it is possible to limit the validity of a message in time and thus to prevent an attacker from using this message again after the validity expires successfully in the network. For example, the receipt of a message whose validity has expired can be discarded or an error message or an alarm can be generated.

Thus, the approach presented here allows the client 102 can verify that he is with a trusted master 101 communicated. Furthermore, master can 101 and client 102 authenticate and verify each other that the synchronization messages were neither inadvertently or intentionally manipulated in content nor delayed more than expected.

The concept presented here offers protection against technical errors as well as against malicious manipulation.

This concept can be efficiently combined with established time synchronization concepts. Existing mechanisms can be supplemented or further used.

LIST OF REFERENCE NUMBERS

101

first component, master (e.g., vehicle control unit)

102

second component, client (e.g., vehicle control unit)

103

Message ("time synchronization request")

104

Message ("Initialization of (time) synchronization")

105

Message ("Synchronization Delay Request")

106

Step to determine T2

107

Message ("Follow-up synchronization delay request")

108

Message ("delay verification")

109

Step to determine T1 and VZ

110

Step to set the system time at the client

t1 to t4

Time

T1

Time Delay

T2

Time Delay

VZ

delay

M1

MAC value

M2

MAC value

ch1

ID

ch2

ID

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• IEEE 802.1X [0002]
• http://en.wikipedia.org/wiki/Man-in-the-Middle-attack [0004]
• http://en.wikipedia.org/wiki/Message_Authentication_Code [0006]

Claims (19)

Method for determining a delay, in which a first component ( 101 ) a second component ( 102 ) a first message ( 104 ) comprising a first identifier (ch1), - in which the second component ( 102 ) of the first component ( 101 ) a second message ( 105 ) comprising a second identifier (ch2), - in which the second component ( 102 ) of the first component ( 101 ) a third message ( 107 comprising first time information (T2; t2, t3) based on a reception time (t2) of the first message (T2) 104 ) and a transmission time (t3) of the second message ( 105 ) together with a first coded value (M1), wherein the first coded value is based on the first time information (T2; t2, t3), - in which the first component ( 101 ) the delay (VZ) is determined based on a transmission time (t1) of the first message, a reception time (t4) of the second message and the first time information (T2; t2, t3) and - in which the first component ( 101 ) checks the first time information (T2; t2, t3) based on the first coded value (M1). Method according to Claim 1, in which the first encoded value (M1) is additionally based on the first identifier (ch1) and on the second identifier (ch2). Method according to one of the preceding claims, in which the first coded value (M1) is determined by means of at least one of the following functions: - a hash function; A cryptographic hash function; - a one-way function; A MAC algorithm, - a symmetric encryption; - asymmetric encryption. - an asymmetric signature algorithm. Method according to one of the preceding claims, wherein the first identifier is determined by the first component based on one of the following information or values: - an identification of the creating network component; An identification of at least one network component; A date information comprising e.g. at least one of the following information: day, month, year, time, hour, minute, second; - a random number; - a number unique in the system; - a validity information. Method according to one of the preceding claims, wherein the second identifier is determined by the second component based on one of the following information or values: - an identification of the creating network component; An identification of at least one network component; A date information comprising e.g. at least one of the following information: day, month, year, time, hour, minute, second; - a random number; - a number unique in the system; - a validity information. Method according to one of the preceding claims, in which the first component ( 101 ) of the second component ( 102 ) a fourth message ( 108 ), the fourth message ( 108 ) comprises the delay (VZ) and a second encoded value (M2), the second encoded value (M2) being based on the delay (VZ). Method according to one of the preceding claims, in which the second encoded value (M2) is determined by means of at least one of the following functions: - a hash function; A cryptographic hash function; - a one-way function; A MAC algorithm, - a symmetric encryption; - asymmetric encryption. - an asymmetric signature algorithm. Method according to one of Claims 6 or 7, in which the fourth message ( 108 ) of the second component ( 102 ) is provided if the verification of the first time information (T2; t2, t3) was successful. Method according to one of Claims 6 to 8, in which the fourth message ( 108 ) additionally the transmission time (t1) of the first message ( 104 ) and in which the second coded value (M2) is additionally recorded on the transmission time (t1) of the first message ( 104 ). Method according to Claim 9, in which the second component ( 102 ) the delay (VZ) and the transmission time (t1) of the first message ( 104 ) is checked on the basis of the second coded value (M2) and, if the check was successful, a time counter of the second component ( 102 ) based on the transmission time (t1) of the first message ( 104 ) and / or the delay (VZ) is changed. Method according to Claim 10, in which the change in the system time of the second component is carried out at predetermined times, in particular regularly or irregularly. Method according to one of Claims 10 or 11, in which the system time of the second component is not changed if the check based on the second coded value was unsuccessful. Method according to one of the preceding claims, wherein the first component and the second component via a network, in particular a bus system or the Ethernet are coupled together. Method according to one of the preceding claims, in which the first component and the second component are control devices of a vehicle. Method according to one of the preceding claims, in which the first component is a time synchronization master and the second component is a client. Method according to one of the preceding claims, wherein the first component and / or the second component comprises a hardware and / or software component. Vehicle with a first component ( 101 ) and a second component ( 102 ), - in which the first component ( 101 ) of the second component ( 102 ) a first message ( 104 ) comprising a first identifier (ch1), - in which the second component ( 102 ) of the first component ( 101 ) a second message ( 105 ) comprising a second identifier (ch2), - in which the second component ( 102 ) of the first component ( 101 ) a third message ( 107 comprising first time information (T2; t2, t3) based on a reception time (t2) of the first message (T2) 104 ) and a transmission time (t3) of the second message ( 105 ) together with a first coded value (M1), wherein the first coded value (M1) is based on the first time information (T2; t2, t3), - in which the first component (M1) 101 ) determines a delay (VZ) based on a transmission time (t1) of the first message, a reception time (t4) of the second message and the first time information (T2; t2, t3) and - in which the first component (VZ) 101 ) checks the first time information (T2; t2, t3) based on the first coded value (M1). Master component ( 101 ) arranged such that - a client component ( 102 ) a first message ( 104 ) comprising a first identifier (ch1), - by the client component ( 102 ) a second message ( 105 ) comprising a second identifier (ch2) is received, - from the client component ( 102 ) a third message ( 107 ) comprising first time information (T2, t2, t3) based on a reception time (t2) of the first message ( 104 ) and a transmission time (t3) of the second message ( 105 ) is received together with a first coded value (M1), wherein the first coded value (M1) is based on the first time information (T2; t2, t3), - a delay (VZ) is determined based on a transmission time (t1) of first message, a reception time (t4) of the second message and the first time information (T2; t2, t3), the first time information (T2; t2, t3) being checked on the basis of the first coded value (M1). Client component ( 102 ) arranged such that - from a master component ( 101 ) a first message ( 104 ) comprising a first identifier (ch1) is received, - the master component ( 101 ) a second message ( 105 ) comprising a second identifier (ch2), - the master component ( 101 ) a third message ( 107 comprising first time information (T2; t2, t3) based on a reception time (t2) of the first message (T2) 104 ) and a transmission time (t3) of the second message ( 105 ) together with a first coded value (M1), the first coded value (M1) being based on the first time information (T2; t2, t3), 101 ) a delay (VZ) can be determined based on a transmission time (t1) of the first message ( 104 ), a reception time (t4) of the second message ( 105 ) and the first time information (T2; t2, t3), wherein the master component ( 101 ) the first time information (T2; t2, t3) is checked on the basis of the first coded value (M1).

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