Method of providing secured data traffic in a computer

Abstract: The invention relates to a method of providing secured data traffic in a computer network, which is provided with a central access control device and computers that are distributed and that can be connected and disconnected to the network, wherein each computer is provided with a key whose authenticity, previous two connecting the computer in the network is checked by the access control device, in order to either authorize or refuse connection. The key of each computer is secret and is only present in the respective computer, in that from this key the computer derives a public key with an algorithm preseeded in the computer that is also present in the access control device, in that the public key is sent by that computer to the access control device which processes the received public key in the algorithm into a check value, in that the access control device sends a check key to the computer that in accordance with the algorithm processes the check key together with the key of that control device, and in that the access control device admits the computer to the network if the response is identical with the check value, and in that the algorithm is geared such that any result from the algorithm can be derived from a plurality of possible input parameters of the algorithm, whereas only the key computer into a response which the computer sends to the access present in the computer supplies the check value.

Description: The invention relates to a method of providing secured data traffic in a computer network, which is provided with a central access control device and computers that are distributed and that can be connected and disconnected to the network, wherein each computer is provided with a key whose authenticity, previous to connecting the computer in the network is checked by the access control device, in order to either authorize or refuse connection. Such a method has long since been known in the practice of computer networks application. Desirably, in such computer networks that may be wireless or wired, only authenticated computers are admitted to the network, in order to secure the integrity of the network. Normally computer users enter a password or the like that is checked for authenticity, and access to the network is refused if the password is incorrect. Such a system involves considerable drawbacks. For example, the known system requires that a register of the authenticated passwords be kept. An additional disadvantage for the user is that he runs the risk of forgetting the password, thereby rendering access to the network impossible. In some circumstances such a situation is very undesirable, for example, in the event of access being sought in a crisis situation to data that is only available via the network. Such a situation might arise with a data network as used in a hospital or a nuclear power station. An important drawback is further the continuous attention required of the management of the computer network in connection with, among other things, successive computers that also have to be authenticated. These problems play a role especially in wireless networks, but are not limited to these. Because the communication occurs trough the air, it is in particular the wireless networks that have a more open character than is the case with a wired network. Moreover, due to this open character there is an increased risk that access keys are overheard, so that unauthorized persons are able to gain access to the network by using the overheard keys. It is the object of the invention to provide a method of secured data traffic in which these problems do not occur, and the application of which is easily implemented. A method of providing secured data traffic in a computer network of the above-mentioned type in which the key of each computer is secret and is only present in the respective computer, and wherein from this key the computer derives a public key with an algorithm predefined in the computer that is also present in the access control device, whereby the public key is sent by that computer to the access control device, is known from EP-A-0,725,512. The method according to the invention is characterized in that the access control device processes the received public key in the algorithm into a check value, that the access control device sends a check key to the computer which in accordance with the algorithm processes the check key together with the key of that computer into a response which the computer sends to the access control device, and in that the access control device admits the computer to the network if the response is identical with the check value, and in that the algorithm is geared such that any result from the algorithm can be derived from a plurality of possible input parameters of the algorithm, whereas only the key present in the computer supplies the check value. As mentioned, the key has to be secret; uniqueness is desirable but not essential. Since the number of possible keys is very large, the chance of two computers having the same key is small, provided they have been chosen randomly. Desirably, the key present in every computer is not accessible to users of the computer and cannot be obtained from it. This is made possible, for example, by saving this secret key in the read only memory in a part that is not accessible to users. The respective key can be entered into the computer once only during its manufacture, just like the algorithm that the computer uses in the method according to the invention. As explained above, this algorithm is also a component of the access control device. As a result of the invention, the public key that can be derived by the computer from its secret key may become openly known since, due to the nature of the algorithm that every result can be derived from a plurality of possible input parameters, it is practically impossible to determine the secret key by knowing the public key and the algorithm. As a result of the message traffic between the access control device and the computer that after receipt of the public key is initiated by the access control device according to the invention, and in which a check key is sent to the computer that processes this together with its secret key into a response that has to identify with the check value derived by the access control device on the basis of the public key, a check will finally be carried out to determine whether the respective computer possesses the correct secret key. The attraction of the method according to the invention is that the authorized public keys may become generally known, without compromising the secret keys of the computers to be coupled to the network. The best network security can be obtained if all the authorized public keys are previously entered into the access control device. Advantageously, however, the method according to the invention may also be realized such that at a first attempt to connect a computer, the access control device authenticates the public key sent by said computer as being an authorized public key. This greatly reduces the problems of controlling the secured network, so that the correct algorithm needs only to be put into the access control device and into the computers produced for the network, and the respective computers have to be provided with secret keys. The results of the invention can be achieved in particular with an embodiment characterized in that the computer derives the public key from its secret key according to the algorithm pb = g pv mod p, in which p is a predetermined prime number, and g is a predetermined base number, and in that the access control device processes the received public key pb into a check value cw in accordance with the algorithm cw = (pb) x mod p, in which x is a predetermined check number, and in that the access control device sends a check key cs to the computer, which is determined according to the algorithm cs = (g) x mod p, in that the computer processes the check key cs in the algorithm a = (cs) pv mod p, in which a is the response the computer sends to the access control device, in that the access control device compares the response a with the check value cw, and if identical, admits the computer to the network. In a further aspect of the invention, in which the method can be applied if there are two or more access control devices, it is desirable that the access control devices be in data-sharing communication, so that after a computer has been coupled via a first access control device, the computer is free to switch to a further access control device. These objects are solved in advantageous manner basically by applying the features laid down in claim 1. Further enhancements being provided by the subclaims. The invention will now be explained in more detail with reference a non-limiting exemplary embodiment with reference to the accompanying Figures 1 and 2. Figure 1 shows a flow sheet of a communication course between the computer and the access control device of the network. Figure 2 shows the communication course represented in Figure 1 in the set-up comprising a computer (station) and an access control device (access point). The communication course between the computer and the access control device will now be elucidated with reference to Figure 1, in which a numeral 1 - 7 indicates some step shown in Figure 2. Figure 1 shows that in the access control device (access point) predetermined values are given to a check number x, a prime number p, and a base number g. The prime number p is also present in the computer ( station) seeking access to the network via the access control device. This computer also knows a secret key pv that is only known to said computer. The computer also knows the base number g. In step 1, the computer derives a public key pb from the secret key pv according to the algorithm pb = g pv mod p in order to obtained access. In step 2, the computer sends this public key pb to the access control device. In step 3, the access control device processes the public key pb into a check value cw in accordance with the formula cw = (pb) x mod p. This identifies the check value with (g pv ) x mod p (Formula 1). In step 4, the access control device subsequently sends a check key cs to the computer, determined according to the algorithm cs = (g) x mod p. In step 5, the computer processes the value cs in the algorithm a = (cs) pv mod p, and in step 6, returns a response a to the access control device. The value of the response a equals (g x ) pv mod p, as shown in Formula 2. In step 7, the access control device compares the value of the response a with the value from cw, and if identical (compare Formula 1 and Formula 2), which is determined by the correct value of the secret key pv, the access control device will allow the computer access to the network. The person skilled in the art appreciates that an algorithm other than that explained in the exemplary embodiment may also meet the prerequisites of each result of the algorithm being derivable from a plurality of possible input parameters, while only the key present in the computer is able to supply the check value. The exemplary embodiment therefore must not be understood to be limiting. The person skilled in the art will also appreciate that with a particular choice of algorithm, the choice of the secret key pv, the prime number p, the base number g, and the check number x, may optionally be pre-set and are not limited to specific values.

Claims: A method of providing secured data traffic in a computer network, which is provided with a central access control device and computers that are distributed and that can be connected and disconnected to the network, wherein each computer is provided with a key whose authenticity, previous to connecting the computer in the network is checked by the access control device, in order to either authorize or refuse connection, wherein the key (pv) of each computer is secret and is only present in the respective computer, and wherein from this key (pv) the computer derives a public key (pb) with an algorithm predefined in the computer that is also present in the access control device, whereby the public key (pb) is sent by that computer to the access control device, characterized in that the access control device processes the received public key (pb) in the algorithm into a check value, that the access control device sends a check key to the computer which in accordance with the algorithm processes the check key together with the key (pv) of that control device, and in that the access control device admits the computer to the network if the response is identical with the check value, and in that the algorithm is geared such that any result from the algorithm can be derived from a plurality of possible input parameters of the algorithm, whereas only the key present in the computer supplies the check value. A method according to claim 1, characterized in that the key has been permanently programmed into the computer once only. A method according to claim 1, characterized in that at a first attempt to connect a computer, the access control device authenticates the public key (pb) sent by said computer as being an authorized public key. A method according to one of the claims 1 - 3, characterized in that the computer derives the public key (pb) from its secret key (pv) according to the algorithm pb = g pv mod p, in which p is a predetermined prime number, and g is a predetermined base number, and in that the access control device processes the received public key (pb) pb into a check value (cw) in accordance with the algorithm cw = (pb) x mod p in which x is a predetermined check number, and in that the access control device sends a check key (cs) to the computer, which is determined according to the algorithm cs = (g) x mod p in that the computer processes the check key (cs) in the algorithm a = (cs) pv mod p in which a is the response the computer sends to the access control device, in that the access control device compares the response a with the check value (cw), and if identical, admits the computer to the network. A method according to one of the claims 1-4, characterized in that the access control devices are in data-sharing communication, so that after a computer has been coupled via a first access control device, the computer is free to switch to a further access control device.

Inventors: BROCKMANN RONALD ALEXANDER, HOEBEN MAARTEN, ZWEMMER ARNOUD RODERICK, BROCKMANN, RONALD ALEXANDER, HOEBEN, MAARTEN, ZWEMMER, ARNOUD RODERICK
Applicants: NO WIRES NEEDED B V, NO WIRES NEEDED B.V.
Application year: 2000
Main classification: G06F1
IPC codes: G06F21