WO2002058319A1

WO2002058319A1 - Method, program and arrangement for secure information transmission in a communication network

Info

Publication number: WO2002058319A1
Application number: PCT/DE2002/000124
Authority: WO
Inventors: Martin Euchner
Original assignee: Siemens Aktiengesellschaft
Priority date: 2001-01-19
Filing date: 2002-01-17
Publication date: 2002-07-25
Also published as: DE10102368A1

Abstract

A communication network with at least two terminals (A, B) and at least one central unit (C) for the management of codes (K), in which a code is disclosed (KAC, KBC) between each of the two terminals (A, B) and the central unit (C), with which the information to be secured can be transmitted between the both terminals (A, B) and the central unit (C) in a secure manner. Furthermore, a code (KAB) is transmitted from the central unit (C) to the both terminals (A, B), using the codes (KAC, KBC), by means of which information to be secured may be securely transmitted between the both terminals (A, B).

Description

description

METHOD, PROGRAM AND ARRANGEMENT FOR SECURE INFORMATION TRANSMISSION IN A COMMUNICATION NETWORK

In the past, two main types of communication networks for transmitting information have emerged: packet-oriented data networks and line-oriented voice networks. They differed among others due to their different requirements for quality of service and security.

Quality of service - also called 'Quality of Service (QoS)' - is defined differently depending on the context and subsequently evaluated with different metrics. Known examples of metrics for measuring quality of service are the number of non-transmitted information (loss rate), the - possibly averaged - time delay in the transmission (delay) or the number of information not even allowed to be transmitted (blocking rate) ).

Security includes e.g. Authentication and authorization of the participants as well as integrity and confidentiality of the information transmitted. Authentication is the unique identification of the sending participant, authorization the assignment of authorizations, integrity the guarantee of genuine information and confidentiality the encryption of the information so that third parties cannot understand its content.

A distinction is made between symmetrical and asymmetrical encryption. In comparison to coding and decoding, symmetrical encryption methods are considerably faster than asymmetrical methods. With symmetric encryption, the sender and recipient usually share a shared secret - also called a 'key' - with the help of which the encrypted encrypted information can be encoded and decoded. With asymmetrical encryption, each party has a private secret ('private key') to which a publicly known key ('public key') is generated. If information is encoded by a sender with the public key of a receiver, it can only be decoded by the receiver with its private key. This ensures the confidentiality of the information sent because only the recipient can decode the information. Alternatively, information can also be encoded using the transmitter's private key and decoded by each receiver using the transmitter's public key. As a result, the transmitter is authenticated securely, because the decoding is only successful if the information has been provided with the private key known only to the transmitter. This procedure is also known as a 'digital signature' or 'signature'. In this context, so-called 'certificates' according to the ITU standard X.509 are used. This is a public key of a participant certified by a trust center or a certification authority. Certificates are sometimes also transmitted in-band, for example if the communication partners do not yet know the partners' certificates or to speed up processing.

An exception to the principle of confidentiality through encryption is so-called sovereign eavesdropping - also called 'lawfull interception' - which can be ordered by state regulators and / or courts, for example when investigating criminal offenses. A high-quality security concept must provide a way to undo an existing confidentiality mechanism in order to enable eavesdropping. This can be done, for example, by announcing the keys used. In this context, 'key recovery' is understood to mean the reconstruction of a lost key, while the use of a key, for example for sovereign listening, by an authorized, trustworthy third party Instance is referred to as 'Key Escrow'.

Line-oriented voice networks are designed for the transmission of continuously flowing (voice) information, also referred to in the professional world as 'conversation', 'call' or 'session'. The information is usually transmitted with high quality of service and security. For example, a minimum for speech - e.g. <200 ms - Delay without fluctuations in the delay time (delay jitter) is important, since speech requires a continuous flow of information in the receiving device. A loss of information can therefore not be compensated for by retransmitting the information which has not been transmitted and usually leads to an acoustically perceptible crack in the receiving device. In the professional world, the transmission of language is also generally referred to as a 'real-time (transmission) service' or as a 'real-time service'. The quality of service is achieved through appropriate dimensioning and planning of the voice networks, with the transmission capacity generally due to the line orientation. is not subject to fluctuations. Security is achieved, for example, by appropriate spatial and organizational partitioning of the voice networks against unauthorized third parties. For example, in the past responsibility for voice networks is often state-owned, which means e.g. eavesdropping by third parties was largely ruled out.

Packet-oriented data networks are designed for the transmission of packet streams also referred to in the technical field as 'data packet streams'. It is usually not necessary to guarantee a high quality of service. Without guaranteed quality of service, the transmission of the data packet streams takes place, for example, with delays which fluctuate over time, since the individual data packets of the data packet streams are usually transmitted in the order in which they are accessed, ie the more packets from a data network, the greater the time delays are to be transmitted. In the professional world, the transmission of data is therefore also referred to as a transmission service without real-time conditions or as a 'non-realtime service'. Security plays a subordinate role. In smaller networks such as local area networks (LAN) or company networks (Corporate Network - also called Virtual Private Network (VPN)), this is mostly achieved by spatial partitioning of the networks, since you can only find participants in these networks who are authorized from the start are (so-called 'friendly users').

The best known data network at the moment is the Internet. The Internet is designed as an open (wide area) data network with open interfaces for connecting (mostly local and regional) data networks from different manufacturers. So far, the main focus has been on providing a manufacturer-independent transport platform. Adequate mechanisms to guarantee quality of service and security play a secondary role. For this reason, increased security is currently being implemented primarily with decentralized filter devices - also called 'firewalls' - located at the interfaces to the Internet. Network-internal quality of service and security mechanisms, however, are hardly yet available. In particular, key recovery and key escrow are unknown in the known IP-based voice and / or data networks.

In the course of the convergence of line-oriented voice and packet-oriented data networks, voice transmission services and, in the future, broadband services such as the transmission of moving image information will also be implemented in packet-oriented data networks, ie the real-time services that were previously usually line-oriented are transmitted in a convergent voice-data network packet-oriented, ie in packet streams. These are also called 'real-time packet streams'. The problem that arises here is that a high quality of service and security are required for a packet-oriented implementation of a real-time service is so that it can be compared qualitatively with a line-oriented transmission, while modern data networks and especially the Internet do not provide adequate mechanisms to guarantee high quality of service and security.

In the following, the focus is on voice transmission on the Internet. However, this is not a significant restriction, because the quality of service and security requirements are not specifically designed for the Internet, but generally apply to all types of data networks. They are independent of the specific design of a data network. The packets can consequently be designed as Internet, X.25 or frame relay packets, but also as ATM cells. They are sometimes referred to as 'news', especially then when a message is delivered in a packet. Data packet streams and real-time packet streams are exemplary embodiments of traffic streams transmitted in communication networks. Traffic flows are also referred to as 'connections', even in packet-oriented networks, in which connectionless transmission technology is used. For example, information is transmitted in TCP / IP using so-called flows, through which the sender and receiver (e.g. web server and browser) are connected to one another at a logically abstract level despite the connectionless nature of IP, i.e. Logically abstracted, flows also represent connections.

Several architectures are described in the international standardization committees IETF (Internet Engineering Task Force) and ITÜ (International Telecommunications Union) for the transmission of voice and image information via the packet-oriented Internet - also called 'VoIP'. What they all have in common is that the call control level and the resource control level are functionally separated from one another.

The central element of the call control level is a call controller, to which the following functions are assigned: - Implementation of E.164 phone numbers on computer names or their Internet addresses

- Admissibility check- for incoming and outgoing calls

- Management of transmission capacities - Registration of VoIP devices

Examples of call controllers are the 'gatekeeper' proposed by the ITU in the H.323 standard family or the 'SIP proxy' proposed by the IETF. If a larger communication network is divided into several domains - also called 'zones' , usually at least one separate call controller is provided in each domain.

The resource control level u includes as a central element a resource controller, which among other things the following functions are assigned:

control the volume of traffic delivered to the communication network by packet streams;

- if necessary, reserve resources in the communication network for a prioritized packet stream in order to transmit them;

- set priority flags in the packets according to the priority of their packet streams;

- Check the priority indicator of packet streams and correct if necessary if the packets are already labeled with priorities;

- control the transmission capacity of packet streams.

The resource controller is also known as a 'Policy Decision Point (PDP)'. It is often within so-called 'edge routers' - also 'edge devices', 'access nodes' or at

Assignment to an Internet Service Provider (ISP) called 'Provider Edge Router (PER)' - implemented. Alternatively, the PER can only act as a proxy and forward the resource controller-relevant information to a separate server on which the resource controller is implemented. d 1 e TJ 1 1 o 1

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tokoll, which occurs according to the ITU standard H.225.0 between the end points of the connection and the assigned gatekeepers, as well as similarly designed messages. Signaling protocols according to the ITU are e.g. in the standard H.225.0, "Media Stream Packetization and Synchronization on Non-Guaranteed QoS LANs", 2000, which according to the IETF in RFC 2453bis, "SIP: Session Initiation Protocol", draft-ietf-sip-rfc2453bis-02.txt , 09/2000. The "actual information" is also known as "useful information", "media information" or "media data" to distinguish it from the signaling.

In this context, an 'out-of-band' means the transmission of certain information (e.g. to be key) in a different way / medium than the routes provided in the communication network for the transmission of signaling and useful information. In contrast, with 'in-band' the specific information is transmitted together, but usually logically separated from the signaling and useful information under consideration.

A call setup is understood here to mean the establishment of the (transport) connection, the signaling for the call, possibly security and other handshakes, and the start of (voice) data transmission. A fast, efficient connection with a short delay, a short round trip with as few additional flows or handshakes as possible is also referred to as 'Fast Connect'.

Based on what has been said so far, it is clear that the implementation of VoIP is only accepted by the participants if the associated signaling data and the media data in the form of voice are transmitted with the same security in the integrated voice data network as in the voice network.

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Accordingly, a secret is agreed in a communication network with at least two terminals and at least one central instance for managing secrets between the two terminals and the central instance, with which information to be secured is securely transmitted between the two terminals and the central instance. The central entity then transmits a third secret to the two end devices in a secure manner by the respective first or second secret, with which information to be secured is securely transmitted between the two end devices. This has the following advantages:

As a result of the distribution of the keys by the central entity and the early establishment of secure channels between the central entity and the end devices, the need for time-consuming Diffie-Hellman handshake protocol operations to generate a common secret in the end devices during call setup is eliminated. This results in a quick connection establishment - problem Pl.

According to the invention, the central instance for the management of secrets is assigned a central role in the generation and distribution of secrets. This makes it easy to define, monitor and enforce a security policy - problem P2.

The secrets are not only known to the end devices, but also to the central authority. Thus, if a key is lost in the end devices, key recovery can be carried out by reloading the lost secrets - problem P3.

The central instance can take measures for key recovery, key-escrow and lawful interception, for example by storing the third secret while the connection is established, and thus can be passed on to authorized third parties - problem P4.

- The media key distribution is carried out quickly and securely by transmitting the third secret on the secure channels between the central instance and the two end devices, since the first two secrets used for this have already been agreed - problem P5.

In addition to these advantages which are directly associated with the solution of the problem, the invention has further essential advantages, some of which are listed below:

- With the symmetrical secrets, the signaling and / or media information can efficiently counter both

Loss of confidentiality as well as protection against integrity violations.

The complexity of the end devices is reduced because the key management and especially the key generation is carried out centrally.

- Parts of already existing SSL / TLS or IPSEC implementations can be reused if existing systems are expanded according to the invention. This reduces the expansion effort.

By eliminating the security handshake integrated with SSL / TLS or IPSEC, not only can computing time be saved, but also the latency can be reduced. This gives you the option of implementing Fast Connect using these existing protocols.

- If the SSL / TLS data protection protocol is also available on ÜDP, the signaling transmitted with ÜDP can also be protected accordingly. This extends the range of uses of the security procedure and increases the

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In a variant of the invention, a changed third secret is repeatedly transmitted from the central entity to the two terminals during the existence of a connection between the two terminals - claim 3. This increases security, especially since the distribution of the changed third secret takes place securely.

According to one embodiment of the invention, the information to be secured between the first terminal and the central instance and between the second terminal and the central instance is designed as signaling information and between the two terminals as signaling information and / or as media information any information exchanged between the units involved is transmitted securely.

In a preferred embodiment of the invention, the central instance is assigned to or integrated into a trustworthy call controller - claim 5. Thus, the need for separate addressing of the central instance is eliminated for the terminals.

In an embodiment of the preferred embodiment of the invention, the call controller is designed as a SIP proxy or as a gatekeeper - claim 6. The invention can thus be inserted into existing installations.

According to a development of the invention, at least one port for transmitting the information between the two terminals is activated by the central entity in at least one firewall arranged between the two terminals when the connection is established between the two terminals - claim 7. From the firewall the negotiation of media ports for the transmission of information between the two end devices therefore need not be followed. This advantage is particularly nice for encrypted signaling between the two end devices, because here the firewall has no way of following the signaling without knowing the third secret.

Further advantageous refinements of the invention result from the subordinate or subordinate claims.

The invention is explained in more detail below on the basis of exemplary embodiments which are illustrated in the figures. It shows:

Figure 1 shows an arrangement for performing the method according to the invention with a central entity for management of secrets and programs for performing the method according to the invention

Figure 2 is a flowchart in which an embodiment of the inventive method is shown as an example

Figure 3 is a flowchart in which an alternative embodiment of the method according to the invention is shown as an example

FIG. 1 shows an exemplary arrangement for carrying out the method according to the invention, which is designed as a communication network KN with two terminals A, B and a central entity C for managing secrets K. 1 1 H 1

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in order that the key management and authentication protocol (SSL handshake) of the SSL / TLS protocol can be omitted, since the secret K _{AB is} already provided in both terminals A, B according to the invention.

To further increase security, a modified third secret K _A B is transmitted to the two terminals A, B repeatedly. For example, this takes place at regular intervals of a few seconds. Listening to unauthorized third parties is effectively made difficult even if they can decrypt the secret K _AB with the help of a powerful decipherer, since experience has shown that deciphering takes several seconds even under optimal conditions. It is clear to the _person skilled in the art that the secrets _KÄC and K _BC are changed repeatedly for the same reason, so that an unauthorized third party does not listen to the connections _VÄC and / or the third secret K _AB required for listening to the media data MEDIA DATA V _{BC is} known.

The end of the call CALL is initiated, for example, by the terminal B by transmitting a message RELEASE COMPLETE to the gatekeeper GK and from this to the terminal A, among other things. After the call CALL has ended, the secret K _AB in the terminals A, B and the central instance C can be deleted. The secrets K _AC and K _BC remain stored in the terminals A, B and the central instance C even after calls CALL have ended and are changed repeatedly, if necessary.

Of course, separate messages for the transmission of the information relevant to the invention are also possible. As a further alternative, the two secrets K _AC , K _{BC can} also be configured manually. This eliminates the use of a complex Diffie-Hellman method DH when registering the terminals A, B at the expense of a reduced flexibility of the arrangement, which in a corresponding way rigidly configured communication network KN can be quite useful and desirable. A corresponding embodiment of the method is shown in FIG. 3. The secrets K _AC , K _B in the terminals A, B and the central instance C are manually preconfigured. The signaling relating to registration and call setup is transmitted securely through the secrets K _AC , K _BC .

As a result of storing the secrets K in the central instance C, efficient measures for key recovery can also be taken, for example if a secret K is lost in one of the terminals. In addition, by passing on the secret K _AB stored in the central instance to authorized third parties, an efficient lawfull interception can be brought about.

In conclusion, it should be emphasized that the description of the components of the communication network KN relevant for the invention is in principle not to be understood as restricting. It is particularly obvious to a person skilled in the art that terms such as “terminal device” or “central instance” are to be understood functionally and not physically. Thus, the terminal devices A, B and the central instance C can, for example, also partially or completely in software and / or via several physical devices can be realized distributed.

Claims

claims

1. A method for secure information transmission in a communication network with at least two terminals (A, B) and at least one central entity (C) for the management of secrets (K), with the following steps: between the first terminal (A) and the central entity ( C) at least a first secret (K _ÄC ) is agreed, with which information to be secured is securely transmitted between the first terminal (A) and the central instance (C), between the second terminal (B) and the central instance ( C) at least one second secret (K _BC ) is agreed, with which information to be secured is securely transmitted between the second terminal (B) and the central entity (C), at least a third secret (K _AB ) to the first terminal (A) secured by the first secret (K _AC ) and to the second terminal secured by the second secret (K _BC ) with which information to be secured is transmitted be securely transmitted between the two terminals (A, B).

2. The method according to claim 1, wherein the first two secrets (K _AC , K _BC ) each time the two terminals (A, B) are registered and the third secret (K _AB ) when a connection (V) is established between the two terminals (A, B) is transmitted.

3. The method according to any one of claims 1 or 2, wherein during the existence of a connection (V) between the two terminals (A, B) from the central entity (C) repeats a changed third secret (K _AB ) to the two terminals (A, B) is transmitted.

4. The method according to any one of claims 1 to 3, wherein the information to be secured between the first terminal (A) and the central entity (C) and between the second terminal (B) and the central entity (C) as signaling information and between the two terminals (A, B) as signaling information and / or as media information.

5. The method according to any one of the preceding claims, wherein the central entity (C) is assigned to a trustworthy call controller or is integrated into this.

6. The method according to claim 5, wherein the call controller is designed as a SIP proxy (SP) or as a gatekeeper (GK).

7. The method according to any one of the preceding claims, in which in at least one between the two terminals (A, B) arranged firewall (F) from the central instance (C) when establishing the connection (V) between the two terminals (A, B ) at least one port for transmitting the information between the two terminals (A, B) is activated.

8. Central authority (C) for the management of secrets (K), which is used to carry out a method according to one of the preceding claims.

9. Program (P) comprising software code sections with which a method according to one of claims 1 to 7 is carried out by a processor.

10. Arrangement for performing a method according to one of claims 1 to 7.