WO2005013551A1

WO2005013551A1 - Method and security system for recognizing an unaltered subscriber identity in a receiver

Info

Publication number: WO2005013551A1
Application number: PCT/EP2004/007728
Authority: WO
Inventors: Georg Krause; Rudy Hartono
Original assignee: Georg Krause; Rudy Hartono
Priority date: 2003-07-18
Filing date: 2004-07-13
Publication date: 2005-02-10
Also published as: DE10333048A1; EP1647108A1

Abstract

The invention relates to a method and a security system for recognizing the unaltered identity of a subscriber who sends a message in a subscriber receiving said message, wherein the subscribers can be interconnected by means of a computer network, particularly the public Internet. The invention also relates to a registering device to be used in the security system. The invention also aims at solving the technical problem of providing the receiver with an improved mechanism for blocking web information (spam) sent via email. This is achieved in that the subscribers (10, 20) are registered in the registering devices (30, 40) and in that a method is provided, which makes it possible for the receiver of a message to verify the integrity of the identity of the sender of the information..

Description

Method and security system for recognizing a genuine subscriber identity at a recipient

description

The invention relates to a method and a security system for recognizing an unadulterated identity of a subscriber sending a message to a subscriber receiving this message, the subscribers being able to be connected to one another via a computer network, in particular the public Internet. The invention is also directed to a registration device for use in the security system.

A disadvantage of existing computer networks, such as the public Internet, is that sender information is often not given or forged. The regular falsification of sender addresses means that, for example, unwanted e-mail advertising mailings at the recipient cannot be effectively suppressed using filter techniques. As a result, the proportion of unwanted information increases rapidly and storage capacity is thus occupied. In existing network protocols such as the Internet protocol or the protocols used for e-mail, there are none

Mechanisms that enable a secure verification of the sender's identity.

A number of methods are currently known, all using digital signatures to identify the identity of the

Prove sender. However, the procedures assume that it is in the sender's interest to prove his identity properly. The known methods therefore require cooperative support from the sender.

There are currently no known procedures that force the sender to disclose their identity. The known problem with unwanted advertising mail on the Internet (spam) would otherwise not exist.

The invention is therefore based on the object of providing a method, a security system and a registration device by means of which it is possible to recognize at the recipient of a message that the identity of the message sender has not been falsified.

The above-mentioned technical problem is solved on the one hand by the features of claim 1.

A method for recognizing an unadulterated identity of a subscriber sending a message to a subscriber receiving this message is then provided. Participants can be connected to each other via a computer network. The process has the following steps:

The individual identities of several participants are stored in at least one registration facility; at least one individual participant key is generated for each participant; Before the start of the transmission of a message from an originating participant to at least one target participant, it is checked whether the individual identities of the originating and target participants are stored in the at least one registration device; if so, the identity of the originating subscriber is encrypted with the individual subscriber key of the target subscriber ^• and a first encrypted value is formed; the first encrypted value is transmitted to the originating participant; a message, the identity of the originating party and the first encrypted value are sent from the original party to the destination party; the first encrypted value is decrypted using the target subscriber's individual subscriber key in order to obtain the _. obtain decrypted identity of the originating participant; the decrypted identity of the originating party is compared to the unencrypted transmitted identity of the originating party; if the compared identities match, the received message is forwarded for further processing. This ensures that only messages for further processing - e.g. B. for storage, output on a display - that have been received by an originating participant with a genuine identity.

In order to prevent the received message from being manipulated on the transmission path, the message is appropriately secured, for example encrypted. The invention achieves this by the following steps: If the comparison shows that the individual identities sent by the originating participant, namely the identity of the originating and destination participant, are stored in the at least one registration device, a cryptographic key is generated; the cryptographic key is associated with the identity of the originating subscriber, wherein the obtained value is then ^'encrypted with the individual subscriber key of the destination subscriber, and forms the first encrypted value; the cryptographic key is encrypted with the individual subscriber key of the originating subscriber and forms a second encrypted value; the first and second encrypted values are transmitted to the originating party; the originating party decrypts the second encrypted value with the originating party's individual subscriber key to obtain the cryptographic key; the message to be sent is secured, for example encrypted, using the cryptographic key; the secured message, the identity of the originating party and the first encrypted value are sent from the originating party to the destination party; the first encrypted value is decrypted with ^'the individual subscriber key of the destination subscriber, to obtain the decrypted identity of the originating subscriber and the cryptographic key; the decrypted identity of the originating participant is compared with the identity of the originating participant transmitted in clear text; if the compared identities match, the received message is unlocked with the cryptographic key, for example decrypted, and forwarded for further processing.

The degree of security of the method can be increased in that the useful life of the cryptographic key for the originating participant and / or the Target participant is limited in time.

For this purpose, the time of generation of the cryptographic key is determined and saved. The use of the cryptographic key by the originating and / or target subscriber is blocked after a predetermined period of time with reference to the determined point in time.

The method can also be used if the origin and destination participants are assigned to different registration facilities.

This is achieved in that the originating participants send the individual identities of the originating and destination participants to the registration device assigned to them before the transmission of a message; it is then checked whether the individual identities of the origin and destination participants are stored in this registration device; if only the individual identity of the originating participant is stored, the registration device is searched in which the identity of the target participant is stored.

With the aid of the method, it is possible to determine on the recipient side the participants whose sent messages are to be specifically discarded or accepted. In this way, advertising waste (spam) sent by e-mail can be intercepted in a targeted manner. For this purpose, predetermined identities of other participants are stored in the participants, whose sent messages are rejected or forwarded to a corresponding target participant. The identities are preferably subscriber addresses, in particular e-mail addresses. The cryptographic key can be generated according to a conventional random algorithm. .

The above technical problem is also caused by a security system for the secure transmission of a

Participant identity resolved from an originating participant to a target participant. The security system comprises a communication network, in particular a public computer network, at least two participants who can act as origin and / or destination participants and are connected to the communication network, and at least one registration device assigned to the participants. The registration device has the following features: at least one subscriber connection interface, a storage device in which at least the identity of a subscriber is stored, a device for generating individual subscriber keys in response to the at least one stored identity and for sending the individual subscriber keys to the associated subscribers , a device for comparing the identity sent by a source and / or destination with the stored identities, a first device for encrypting the identity of the source with the individual

Subscriber key of the target subscriber, so that a first encrypted value is generated, which is intended for the originating subscriber, the originating subscriber having the following features: a device for communication with the registration device and the target subscriber, the target subscriber having the following features: a device for decrypting the first encrypted value with the individual Subscriber key of the target subscriber in order to obtain the decrypted identity of the originating subscriber, a device for comparing the decrypted identity of the originating subscriber with the unencrypted transmitted identity of the originating subscriber, a device for further processing a message received from the originating subscriber if the compared identities match.

The originating participant is connected to the communication network via the communication device, so that a connection is made both to the destination participant and to the registration device via the communication network. Alternatively, the communication device can have two separate interfaces which connect the originating participant to the communication network and to the registration device.

In order to be able to transmit a secure, preferably encrypted message from the originating participant to the target participant, the registration device also has: a device for generating a cryptographic key, a device for linking the cryptographic key

Key with the identity of the originating subscriber, the first encryption device being designed to encrypt the value supplied by the linking device with the individual subscriber key of the target subscriber and delivering the first encrypted value, a second encryption device for generating a second encrypted value by encrypting the cryptographic key with the individual Participant key of the original participant, the originating subscriber having the following further features: a device for decrypting the second encrypted value with its individual subscriber key in order to obtain the cryptographic key; means for securing a message to be sent using the cryptographic key, the communication means (110, 115) for sending the secured message, the identity of the

Originating participant and the first encrypted value to the target participant; the target device having the following further features: an unlocking device, for example a

Decryption device for unlocking the received message using the cryptographic key, the ₍ decryption device being designed to decrypt the first encrypted value using the individual subscriber key in order to obtain the decrypted identity of the originating subscriber and the cryptographic key.

The time-limited use of the cryptographic key is achieved in that the registration device has the following further features: a device for determining the point in time at which the cryptographic key was generated, the linking device for linking the cryptographic key with the identity of the originating party and the Time is formed, wherein the at least one registration device, the origin and / or the destination participants a device for calculating the expiry of a predetermined period of time in Have reference to the determined point in time.

Preferably ^', the target subscriber to a device for discarding a received message. This device expediently speaks on the chronological course of the useful life of the cryptographic key. and / or a mismatch between the identity of the decrypted in the target participant

Originating participant and his unencrypted received identity.

Fener, the registration device can have an interface for connecting to at least one further registration device and a device for searching the registration device, which is assigned to the target subscriber or in which the target subscriber is registered by his identity.

The above-mentioned problem is also solved by a registration device which is suitable for use in the security system described above.

The registration device has at least one subscriber connection interface, a storage device in which at least the identity of a subscriber is stored, a device for generating individual subscriber keys in response to the at least one stored identity and for sending the individual subscriber keys to the associated ones

Participants, a device for comparing the identity sent by a source and / or destination participant with the stored identities and a first device for encrypting the identity of the Originating participant with the individual participant key of the target participant, so that a first encrypted value is created which is intended for the originating participant.

The registration device advantageously contains a device for generating a cryptographic key, a device for linking the cryptographic key to the identity of the originating subscriber, the first

Encryption device for encrypting the value supplied by the linking device with the individual subscriber key of the target subscriber and delivering the first encrypted value, and a second encryption device for generating a second encrypted value by encrypting the cryptographic key with the individual subscriber key of the originating subscriber.

The registration device can also have a device for determining the point in time at which the cryptographic key (K _s ) was generated. The linking device is then for linking the cryptographic key with the identity of the

Originating participant and the time is formed.

Furthermore, the registration device can have a device for calculating the expiry of a predetermined period of time in relation to the determined point in time and a device for blocking the use of the cryptographic key. The invention is explained below using an exemplary embodiment in conjunction with the accompanying drawings. Show it:

Fig. 1 shows a schematic representation of the security system according to the invention, Fig. 2 shows the block diagram of a registration device 30/40 shown in Fig. 1, in which the invention is implemented, Fig. 3 shows the block diagram of the originating participant shown in Fig. 1, in which the invention 4 is the block diagram of the target subscriber shown in FIG. 1, in which the invention is implemented. ^'

1 shows a security system which, as a computer network, comprises, for example, the public Internet 50 and two computers 10 and 20 connected to it. The security system also includes two

Registration devices 30 and 40. In the present example, the registration device 30 is connected to the computer 10, whereas the

Registration device 40 is connected to the computer 20. Alternatively, the registration device 30, the computer 10, the registration device 40 and the computer 20 can be connected to one another via the Internet 50. Of course, several computers can be connected to the Internet, several registration devices connected to each other and several computers one

Registration device to be assigned. The interconnected registration devices 30 and 40 can be part of an intelligent network that is superior to the Internet. For the present example, assume that computer 10 is the originating participant of a message and the computer 20 act as the target subscriber of the message.

The structure of the registration devices 30 and 40 is shown in FIG. 2.

The registration devices 30 and 40 have an interface 80, via which they can communicate with the computer 10 or with the computer 20, also shown in FIG. 1 as subscriber A and subscriber B. Data can be transmitted in encrypted form between the registration device 30 and the computer 10 or between the registration device 40 and the computer 20. A memory 60 is connected to the interface 80, in which the identity ID _{A of} the computer 10, for example an e-mail address, the period of use n for using a cryptographic key K _s and the subscriber keys can be stored. For the sake of better illustration only, the memory 60 was represented by two devices, each of which is provided with the reference number 60. A comparator 260 is connected to the interface 80 and the memory 60 in order to be able to compare the identities ID _{A of} the computer 10 and ID _{B of} the computer 20 supplied by the computer 10 with the identities stored in the memory 60. A search device 250 is connected to an interface 100 and the comparator 260 in order, in the event that the identity ID _{B of} the target computer 20 is not stored in the memory 60, to search the registration device, in the present case the registration device 40, in which the identity ID _{B of} the computer 20 is stored. A linking device 190 is connected on the input side to the memory 60 and a key generator 180 and on the output side to an encryption device 200. The key generator 180 is one Timer 230 connected, which determines the time of generating a cryptographic key K _s . The timer 230 may be connected to a timing calculator 270 connected to the memory 60 to determine when the

Service life n of the key Ks has passed. Furthermore, a subscriber key generator 70 is connected to the memory 60 and an encryption device 205. The subscriber key generator 70 generates at least one individual subscriber key for each computer whose identity is stored in the memory 60. In the present example, a subscriber key K _{A is} generated for the computer 10, which can be transmitted to the computer 10 via a secure connection. Similarly, registration device 40 generates one

Subscriber key K _B for the computer 20, which in turn can be transmitted to the computer 20 via a secure connection. The subscriber keys are stored in the memory 60. The encryption device 200 is also connected to the memory 60 and the interface 80. The encryption device 205 is with the

Subscriber key generator 70 and the key generator 180 connected. The interface 80 is also connected to the interface 100. The registration devices 30 and 40 are connected to one another via respective interfaces 100.

FIG. 3 schematically shows the transmitting part of the computer 10, whereas FIG. 4 schematically shows the receiving part of the computer 20. It is obvious that both computers 10 and 20 can contain both a transmitting and a receiving part. The special representation in FIGS. 3 and 4 was only chosen to include the exemplary use of the computer 10 as a news transmitter and the reproduce exemplary use of the computer 20 as a message recipient.

The computer 10 is connected to the registration device 30 via an interface 115 and to the Internet 50 via an interface 110. The computer 10 contains a decryption device 210, an encryption device 230 connected thereto for encrypting a message m to be sent and a key memory 220 which is connected to the decryption device and the

Encryption device 230 can be connected. The encryption device 230 is a possible implementation of a security device.

As FIG. 4 shows, the computer 20 has an interface 120 for connection to the Internet 50 and an interface 130 for communication with the

Registration device 40 on. A decryption device 140 and a comparator 160 are connected to the interface 120. A further decryption device 145 is connected to a decision maker 240

Decryption device 140, the interface 120 and a display 170 for displaying the decrypted message m connected. The display 170 is also connected to the decision maker 240 and the comparator 160. A key store 150 is with the

Decryption device 140 and the interface 120 connected.

The functioning of the security system is explained in more detail below.

The security system works in two stages, a registration phase with the Registration devices 30 and 40 and an operating phase.

The registration phase begins with the identity ID _{A of} the computer 10 in the memory 60 of the

Registration device 30 is stored. The subscriber key generator 70 then creates a subscriber key K _A for the computer 10. The subscriber key K _A is stored in the memory 60 and is preferably encrypted and only transmitted to the computer 10 via the interface 80 and there in the

Key store 220 filed. -In a similar manner, the identity ID _B of the computer is stored in the memory of the registering device 40 twentieth The subscriber key generator 70 of the

The registration device 40 then creates a subscriber key K _B for the computer 20. The subscriber key K _B is stored in the memory 60 of the registration device 40 and is preferably encrypted only via the interface 80

Transfer computer 20 and stored there in a key memory 150. The computers 10 and 20 can agree with the registration device 30 or 40 which encryption method is used for the subsequent operating phase. As already mentioned, the identities of the respectively registered computers, the subscriber keys and the encryption method are stored in the registration devices 30 and 40.

With regard to the operating phase, it is now assumed that the computer 10 wants to send a message m to the computer 20. First, the computer 10 sends a request to the registration device 30 stating its own identity ID _A and the identity ID _{B of} the computer 20 in order to obtain a connection to the computer 20 via the Internet 50. The identities of the computers can be the e-mail addresses. Exactly the same identity information that was already used when registering the computers 10 and 20 in the registration device 30 and 40 must be used.

After receiving identities ID _A and ID _B , comparator 260 of registration device 30 checks whether identity ID _A of computer 10 is stored in memory 60. If the computer 10 is not registered, the request for a connection request to the computer 20 is rejected - and the computer 10 receives a corresponding message. However, in the present case, the comparator 260 confirms that the computer 10 is registered in the registration device 30 and further checks whether the computer 20 is also registered, ie whether the identity ID _B in the memory 60 of the

Registration device 30 is included. This is not the case in the present example. In response to this, the search device 250 of the registration device 30 initiates a search for the registration device in which the computer 20 is registered. Here, the search device 260 can use the specified identity ID _{B of} the computer 20 to find the registration device 40 in which the computer 20 is registered. During the search, the identities ID _A and ID _{B of} the computers 10 and 20 are transmitted to the respective registration device for checking that they match the respectively stored identities. The search can be carried out until the registration device in which the computer 20 is registered is found. As soon as the

The registration device 40 receives the identities ID _A and ID _B from the registration device 30, the checks

Comparator 260 of the registration device 40 as to whether the identity ID _B is stored in the memory 60.

Since the computer 20 is registered in the registration device 40, the key generator 180 generates the

Registration device -40 a random key K _s . The timer 230 of the registration device 40 determines a time stamp t which corresponds to the time at which the random key was generated. The random key K _s is now linked to the identity ID _{A of} the computer 10 and the time stamp t by an algorithm in the linking device 190 of the registration device 40. The algorithm for the linkage is of minor importance and in the simplest case can consist of joining the values together. The linkage value thus formed can be stored in the memory 60 of the registration device 40. The link value is encrypted in the encryption device 200 of the registration device 40 with the aid of the subscriber key K _{B of} the computer 20 and results in the value r. The following applies: r = function E (Ks | IDA | t, K _B )

Thereupon both the value r and the

Random key K _s and, optionally, the useful life n of the random key K _Ξ stored in the memory 60 are sent to the registration device 30 in a confidential manner, usually encrypted. Here is essential that the random key K _s cannot be found out on the transmission path.

In the linking device 190 of the registration device 30, the random key K _{Ξ is} linked to the usage time n. In the

Encryption device 200 forms a value s by encrypting the output value of the linking device 190 with the aid of the subscriber key K _{A of} the computer 10. The following applies: s = function E (Ks | n, K _A )

The values r and s are now sent to the computer 10.

In the decryption device 210 of the computer 10, the value s is decrypted using the subscriber key K _{A of} the computer 10 in order to obtain the random key K _s and the useful life n. The useful life n indicates how long the random key K _s can be used. The following applies:

K _s | t function D (s, K _A )

The message m to be transmitted is now encrypted in the encryption device 230 with the random key K _s , as a result of which the value v is formed. As used in the example, this security can be implemented by means of an encryption function, a key-dependent hash function, an encrypted hash value or by "message authentication code" MAC based on the key K _s . It is only important for the encryption that the encryption function depends on the key K _s and can be inverted without knowledge of the key K _s . The following applies to the value v: v = function E (m, K _s )

The processed message v with the unencrypted identity ID _{A of} the sending computer 10 and the value r is now sent to the computer 20 via the Internet 50.

The computer 20 receives the information v, ID _A and r.

First, the value r is decrypted in the decryption device 140 using the subscriber key K _B stored in the subscriber key memory 150. The following applies: K _s | ID _A | t = function D (r, K _B )

The decrypted value of ID _A and the unencrypted value of ID _A are now compared in comparator 160. If the values are not identical, the identity ID _{A of} the computer 10 has been manipulated. The result is fed to the decision maker 240, who causes further processing, for example the decryption of the message m, not to be carried out or terminated in the decryption device 145. A manipulated sender identity was thus discovered.

However, if the comparator 160 determines, as in the present example, that the compared values for the identity ID _A match, the decision maker 240 optionally checks, based on the transmitted useful life n and the determined point in time when the random key K _{s is generated} , whether the useful life n is related on the determined time stamp t of the generation of the random key K _{s has been} exceeded. If this is the case, the further processing of the encrypted Message m canceled by the decision maker 240 because the key K _{s is} too old.

The expiry of the usage time n of the key K _s can also be determined by the time expiry calculator 270

Registration devices 30 and 40 are determined, whereupon the respective registration device blocks the use of the random key K _s and deletes the key. The expiration of the useful life can also be determined in the sending computer 10.

If the useful life n has not yet expired, the decryption device 145 is released by the decision maker 240 to apply the function D with the key K _s to the encrypted message v. The function D represents a decryption, a key-dependent hash code check, a check of an encrypted hash code or a check of an encrypted MAC. After successful processing of the message m, where m = function D (v, K _s ), the Message for example shown on the display 170, or stored in the computer 20.

With the encryption of the message m in the computer 10, it can be prevented that the message is researched or manipulated via the Internet 50 to the computer 20. For example, any message could be included in a valid combination of the values of ID _A and r. LIST OF REFERENCE NUMBERS

10 computers (participant A) 20 computers (participant B) 30, 40 registration device 50 Internet (communication network) 60 memory for storing identities, keys, useful life n 70 participant key generator 80 interface for connection to participant A or B 90 timer for Determining the time of origin of the key K _s 100 Interface for connecting to the registration device 30 or 40 110 Interface for connecting the computer 10 to the Internet 115 Interface for connecting the computer 10 to the registration device 30

120 Interface for connecting the computer 20 to the Internet

130 Interface for connecting the computer 20 to the registration device 40

140 decryption device for decrypting the first value r with the subscriber key K _B 145 decryption device for decrypting an encrypted message using the key K _s 150 key memory for storing the keys 160 comparator for comparing the decrypted ID _A with the unencrypted transmitted ID _A 170 display

180 key generator for generating a key K _Ξ 90 linking device for linking the ID _A , the K _s and the useful life n 200 encryption device for encrypting the result from the linking device with K _B and for encrypting the ID _A with K _B 205 encryption device for encrypting the key K _s with K _A

210 decryption device for decrypting a second value s using the subscriber key K _{A '} to obtain the key K _s , 220 key memory for storing the keys 230 encryption device for encrypting a message m with the key K _s 240 decision-maker for activating or deactivating the decryption device 145 and the display 170 250 search device 260 comparator for comparing the received ID _A and ID _B with the content of the memory 60 270 timing calculator

Claims

claims

1. A method for recognizing an unadulterated identity of a subscriber (10) sending a message to a subscriber (20) receiving this message, the subscribers (10, 20) being able to be connected to one another via a computer network (50), with the following steps: a ) the individual identities (ID _A , ID _B ) of several participants (10, 20) are stored in at least one registration device (30, 40); b) at least one individual subscriber key (K _A , K _B ) is generated for each subscriber (10, 20); c) before the start of the transmission of a message from an originating participant (10) to at least one target participant (20), it is checked whether the individual identities (ID _A , ID _B ) of the originating and target participants (10, 20) in the at least one registration device ( 30, 40) are stored; d) if yes, the identity (ID _A ) of the originating subscriber (10) is encrypted with the individual subscriber key (K _B ) of the target subscriber (20) and a first encrypted value (r) is formed; e) the first encrypted value (r) is transmitted to the originating participant (10); f) a message (m), the identity (ID _A ) of the originating participant (10) and the first encrypted value (r) are sent from the originating participant (10) to the target participant (20); g) the first encrypted value (r) is decrypted with the individual subscriber key (K _B ) of the target subscriber (20) in order to obtain decrypted identity (ID _A ) of the originating participant (10); h) the decrypted identity (ID _A ) of the originating participant (10) is compared with the unencrypted transmitted identity (ID _A ) of the originating participant (10); i) if the compared identities match, the received message is forwarded for further processing.

2. The method according to claim 1, characterized in that steps d) to i) are replaced by the following steps: if the individual identities (ID _A , ID _B ) of the origin and destination participants (10, 20) in the at least one registration device (30, 40) are stored, a cryptographic key (K _s ) is generated, - the cryptographic key (K _s ) is linked to the identity (ID _A ) of the originating participant (10), the value obtained then being associated with the individual Subscriber key (K _B ) of the target subscriber (20) is encrypted and forms the first encrypted value (r); the cryptographic key (K _s ) is encrypted with the individual subscriber key (K _A ) of the originating subscriber (10) and forms a second encrypted value (s); the first and second encrypted values (r, s) are transmitted to the originating party (10); the originating subscriber (10) decrypts the second encrypted value (s) with the individual subscriber key (K _A ) of the originating subscriber (10) in order to obtain the cryptographic key (K _s ); the message (m) to be sent is saved using the cryptographic key (K _s ); the secured message (m), the identity (ID _A ) of the originating participant (10) and the first encrypted value (r) are sent from the originating participant (10) to the target participant (20); the first encrypted value (r) is decrypted with the individual subscriber key (K _B ) of the target subscriber (20) in order to obtain the decrypted identity (ID _A ) of the originating subscriber (10) and the cryptographic key (K _s ); the decrypted identity (ID _A ) of the originating participant (10) is compared with the unencrypted transmitted identity (ID _A ) of the originating participant (10); if the compared identities match, the received message is unlocked with the cryptographic key (K _Ξ ) and forwarded for further processing.

3. The method according to claim 2, characterized in that the time of generation of the cryptographic key (K _s ) is determined and stored, and that the use of the cryptographic key (K _s ) by the originating and / or target subscriber (10, 20 ) is blocked after a predetermined period of time.

4. The method according to any one of claims 1 to 3, characterized in that step c) according to claim 1 comprises the following steps: before the start of the transmission of a message, the originating participant (10) sends the individual identities (ID _A , ID _B ) of the origin and Target participants (10, 20) to the registration device (30) assigned to them; it is checked whether the individual identities (ID _A , ID _B ) of the origin and destination subscriber (10, 20) are stored in this registration device (30); if only the individual identity (ID _A ) of the originating participant (10) is stored, the registration device (40) is searched in which the identity (ID _B ) of the destination participant (20) is stored.

5. The method according to any one of claims 1 to 4, characterized in that predetermined identities of other participants are stored in the participants (10, 20), the messages sent to a corresponding target participant are rejected or forwarded.

6. The method according to one of the claims 1 to 5, characterized in that the identities are subscriber addresses, in particular email addresses.

7. The method according to claim 2, characterized in that the cryptographic key (K _s ) is generated according to a random algorithm.

8. Security system for recognizing an unadulterated identity of an originating subscriber (10) sending a message in the case of a destination subscriber (20) receiving this message, in particular for carrying out the method according to one of claims 1 to 7, comprising a communication network (50), in particular a public computer network, at least one originating subscriber and at least one target subscriber (10, 20) connected to the communication network (50), and at least one assigned to the subscribers

Registration device (30, 40), the registration device 30, 40) having the following features: at least one subscriber connection interface (80), a storage device (60) in which at least the identity of a subscriber is stored, a device (70) for generating individual subscriber key (K _A , K _B ) in response to the at least one stored identity, a device (260) for comparing that of one

Origin and / or destination subscriber (10, 20) sent identity (ID _A , ID _B ) with the stored identities, a first device (200) for encrypting the identity (ID _A ) of the originating subscriber (10) with the individual subscriber key (K _B ) of the target participant (20), so that a first encrypted value (r) is created which is intended for the originating participant (10), the originating participant (10) having the following features: a device (110, 115) for communicating with the Registration device (30) and the target subscriber (20), the target subscriber (20) having the following features: a device (140) for decrypting the first encrypted value (r) with the individual subscriber key (K _B ) of the target subscriber (20) to obtain the decrypted identity (ID _A ) of the originating party (10), a means (160) for comparing the decrypted identity (ID _A ) of the originating subscriber (10) with the unencrypted transmitted identity (ID _A ) of the originating subscriber (10), a device for further processing (170) a message received from the originating subscriber (10) when the compared identities match.

9. Security system according to claim 8, characterized in that the registration device (30, 40) further comprises: a device (180) for generating a cryptographic key (K _s ), a device (190) for linking the cryptographic key (K _s ) with the identity (ID _A ) of the originating subscriber (10), the first encryption device (200) being designed to encrypt the value supplied by the linking device (190) with the individual subscriber key (K _B ) of the destination subscriber (20) and encrypting the first Value (r), a second encryption device (205) for generating a second encrypted value (s) by encrypting the cryptographic key (K _s ) with the individual subscriber key (K _A ) of the originating subscriber (10), the originating subscriber (10) has the following further features: a device (210) for decrypting the second encrypted en value (s) with its individual subscriber key (K _A ) in order to obtain the cryptographic key (K _s ); means for securing (230) one to one sending message (m) using the cryptographic key (K _s ), the communication device (110, 115) for sending the secured message (m), the identity (ID _A ) of the originating party (10) and the first encrypted value (r ) to the target participant (20); wherein the target device (20) has the following further features: a device (145) for unlocking the received message using the cryptographic key (K _s ), the decryption device (140) for decrypting the first encrypted value (r) using its individual Participant key (K _B ) is designed to obtain the decrypted identity (ID _A ) of the originating participant (10) and the cryptographic key (K _s ).

10. Security system according to claim 9, characterized in that the registration device (30, 40) has the following further features: a device ^' (90) for determining the point in time (t) at which the cryptographic key (K _s ) was generated, wherein the linking device (190) is designed to link the cryptographic key (K _s ) with the identity (ID _A ) of the originating subscriber (10) and the time (t), the at least one registration device (30, 40), the originating and / or the target subscriber (10, 20) a device (270) for calculating the expiry of a predetermined period of time with respect to the have determined time (t).

11. Security system according to claim 10, characterized in that the target subscriber (20) has a device (240) for discarding a received message.

12. Security system according to one of claims 8 to 11, characterized in that the registration device (30) has an interface (100) for connecting to at least one further registration device (40) and a device (250) for searching the registration device (40), is assigned to the Zi ^{'elteilnehmer} (20).

13. Registration device for use in a security system according to one of claims 8 to 12, characterized by at least one subscriber connection interface (80), a storage device (40) in which at least the identity of a subscriber is stored, a device (70) for Generating individual subscriber keys (K _A , K _B ) in response to the at least one stored identity, a device (260) for comparing the identity (ID _A , ID _B ) sent by an origin and / or destination subscriber (10, 20) with the stored identities, a first device (200) for encrypting the identity (ID _A ) of the original subscriber (10) with the individual subscriber key (K _B ) of the target subscriber (20), so that a first encrypted value (r) is generated which is used for the originator is determined.

14. Registration device according to claim 13, characterized by a device (180) for generating a cryptographic key (K _s ), a device (190) for linking the cryptographic key (K _s ) with the identity (ID _A ) of the originating party (10) , wherein the first encryption device (200) is designed to encrypt the value supplied by the linking device (190) with the individual subscriber key (K _B ) of the target subscriber (20) and supplies the first encrypted value (r), a second encryption device (205) for Generating a second encrypted value (s) by encrypting the cryptographic key (K _Ξ ) with the individual subscriber key (K _A ) of the originating subscriber (10).

15. Registration device according to claim 14, characterized by a device (230) for determining the point in time (t) at which the cryptographic key (K _s ) was generated, the linking device (190) for linking the cryptographic key (K _s ) with the identity (ID _A ) of the original participant (10) and the time (t).

16. Registration device according to claim 15, characterized by a device (270) for calculating the expiry of a predetermined period of time in relation to the determined time (t) and a device for blocking the use of the cryptographic key (K _s ).