DE4416595C2 - Process for securing encrypted confidential information transfers - Google Patents

Description

The invention relates to a method in the upper Concept of claim 1 defined in more detail. A such a method is e.g. B. in DE 39 19 734 C1 ben.

The known solutions have a decisive shortcoming on: the possibility of influencing the overall system targeted attacks and thus weakening of the functionalities "Controlling, regulating, monitoring".

In the known solutions / systems, the messages can content (here in the UUS) on the transmission route from Angrei be influenced and / or listened to remotely. Besides, could Attackers import targeted false information and thus attack the integrity. This would lead to misinterpretation and the overall functionality of the system in Fra ge. The system operator would incur unnecessary costs charged.

A key method known from DE 39 19 734 C1 transmission in open communication networks for several Communication services (ISDN) uses an arrangement for Authentication of the subscriber stations (TLNA, TLNB) for Key transfer. This authentication arrangement assigns an arrangement for a first security level Monitoring the time frame for key transmission or an arrangement for the representation of the subscriber agreed key in a reduced form and used for a second security level for authentic ver traffic handling a special key management Control center (SMZ) as a relay station, which is not involved and therefore less attack  should offer opportunities than those otherwise used Key distribution centers. The extra effort is, in particular re at the second security level, substantial and disruptive Outside handles are not excluded with certainty.

When using the UUS to transport signaling, Control and monitoring information in one open Communication system, here EURO-ISDN, there is a risk that unauthorized persons and unauthorized systems or system components the information content in UUS mani can pulse and / or eavesdrop. The significance of the Ge entire system is thereby questioned, and the confidence there is no carelessness. For this reason, as Object of the invention by changing the procedure appropriate safety precautions.

This task is performed by the in the characterizing part of the patent Process 1 listed steps solved.

Advantageous developments of the method are in the Characteristics of claims 2 to 4 described.

It is the principle of the invention, the system identifiers (the corresponding equipment in the branch offices and operations central) and any existing operator passwords to identify those in the branch offices and operations central equipment used and, if applicable, the operator to replace them with so-called certificates.

Modern access security and communication security insurance driving allow the use of smart cards and security module-based process. They can be of any length and arbitrarily complex "passwords" and also system identifiers (qua si system identities). The security against off research is carried out using chip cards and chip card-based security modules in corresponding Si additional security devices with EURO-ISDN interfaces.  

The invention is based on exemplary embodiments explained here:

Components of the certificates:

• - Identity (name) of the branch office equipment and Be drive center and, if applicable, the operator
• - date of issue and date of validity
• - Issuing point (name)  
• - public, personalized key of the outside locations and operations centers of existing equipment  and the operator
• - by the secret key of the issuing office cryptographically secured electronic signature using all the data contained in the certificate a public key cryptographic process.

The message content in the UUS also becomes authentic transmitted "session keys" between the Branch offices and control centers are encrypted and therefore protected against attacks.

Explanation of the authentically transmitted Session key.

Operations center and branch office run one session-specific authentication (e.g. after the challenge and response procedures) using their secret "system key" through; one generates of the equipment involved a session key (symmetric key) and sends it as encrypted Information to the other equipment using it public key.

It is the responsibility of the operations center or operating, such as long (period) an authentically transmitted Session key between the operations center and one Branch office is used.

According to the settings of the operating (Time interval for using the same key) generates the security direction of the operations center a new encryption key and transfers it with a corresponding command in the UUS to the branch office. So that is ensures that others are set in adjustable time intervals Keys are used.  

The functional sequence is under the conditions:

• - Installation of the safety device in the / the Operations center / s and entering the ISDN number of the Branch offices,
• - functional ISDN connection,
• - Installation of the safety device in the outside and enter the ISDN number of the person responsible Operations center / s and
• - functional ISDN connection,

to explain as follows:

After installing the safety device outside and enter the ISDN number of the operations center a connection is established automatically or manually (call for Urinitialization) from the "module" via the safety device to the operations center. (Internal use of the UUS between module and safety device)

The branch office's security facility is now building one Connection (in EURO-ISDN) to the security device in the Operations center and requests a B channel for data transfer to.

The two safety devices agree on one "Urinitialization for a branch office". Then there is a mutual session-specific authentication, genius tion of a "session key" and authentic and ver confidential transfer of the same to the branch office.

The session key is in the security modules for UUS usage saved unexplainably. After that the Connection cleared and the B channel can be used by other users applications are used.

In addition, the safety device SEZ in the Central generate a branch ID and as  Send confidential information to the branch and internally to save. In this case, the SE would be the branch office save this ID and use it as def. UUS info to the module pass on.

Whenever the module sends a command or message to the SE sends, the ID of the module with the ID in the SE checked.

The SEZ in the operations center sends information the central facility. Application to the branch office (ISDN phone number) can be used (if necessary, the ID is included transfer).

The central facility lines up the branch office in the Call list on (if necessary, ID branch office is Rights file added).

The SEZ complements its secured, access-protected file ISDN phone number / current Key and monitors the "Generation time key".

Once the central facility due to the internal Call up a call list (time-controlled) to a branch office wants, it sends the ISDN number of the branch and that Corresponding info field as UUS info to your SEZ. This brings the corresponds to session key and encrypts the UUS frame or parts of the UUS frame and sends this to the network.

The SEA of the branch office decrypts the UUS frame and sends it him to the module. The module evaluates and sends as an answer UUS frame (possibly with ID) and ISDN number of the control center SEZ.

The SEA encrypts and transmits UUS frames or frame parts ISDN phone number and UUS frame to the network.  

SEZ headquarters decrypts UUS-FRame and passes it on to the central facility further. This evaluates and initiates additional.

Important: Upon receipt of UUS from the branch office on request the B channel is not set up by the control center.

The branch office can also choose between 2 events / Report alarms to the control center.

It sends the ISDN number of the head office and the UUS frame the SEA. This encrypts the UUS frame or parts and sends the info on the net. The central SEZ decoded UUS and gives frame to the central facility. This evaluates and sends frame to SEZ accordingly. This sends UUS frame to branch after encryption.

At certain intervals there is a change of session key required.

Two alternatives are conceivable:

• 1st SEZ in the control center monitors generation time and generates a new key when it expires. This one sends it encrypted to the old key of the SEA an outpost.
• 2. Same procedure as for urinalisation, but with the note "key change".

Claims (4)

1. Procedure for securing encrypted confidential information transmissions in open communication systems, in particular signaling, control and monitoring information, in the user-user signaling (UUS) of the D-channel (D-channel) of the Pan European Integrated Services Digital Network (ISDN) (in Germany EURO-ISDN) after encryption and against authentication on the side between branch offices and centers, to which security modules are assigned, characterized in that

• 1. After installing a security device (SEA) in the module of a branch and entering the ISDN number, the module first requests a connection via the security device (SEA) to the control center for urinitization, which is carried out by the security device of the branch (SEA) then to the Sicherheitein direction of the central office (SEZ) (or later for the purpose of key change also in the opposite direction) with the request of a B-channel for data transmission that
• 2. after a mutual session-specific authentication with generation and authentic and confidential transmission of a session key is carried out from the central to the branch office, where it is saved as a UUS frame (frame) that cannot be researched for UUS use
• 3. then this branch with an identification (ID), ISDN number and key stored in a secure to handle-protected call list of the center for timed polling and this first B-channel connection is released, and that
• 4. Then, with renewed connections (time-controlled from SEZ to SEA or in the case of events / alarm messages from SEA to SEZ), the ISDN phone number and UUS frame are sent, after which the remote station at least partially uses the UUS frame with the current one The session key is encrypted and sent over the network to the calling party, which decrypts the UUS frame, sends it to the module for evaluation, and sends the UUS frame and ISDN number again in response.

2. The method according to claim 1, characterized in that the later key change after a fixed set time limits by means of a new session index vidual authentication with generation and authenti neat and confidential session key transmission is carried out. 3. The method according to claim 1, characterized in that the key change in the UUS frame (frame) under groove a confidential new session key (S-key) is carried out. 4. The method according to claim 1, characterized in that through the security facility of the headquarters (SEZ) ei ne identification (ID) generated as confidential information formation sent to the branch office and internally (SEZ) and in the security facility of the branch office (SEA) saved and added to the UUS frame.