Patent Publication Number: US-6703923-B2

Title: Apparatus for providing security on a powerline-modem network

Description:
BACKGROUND 
     1. Technical Field 
     This disclosure relates to power-line modem networks, and more particularly, to an apparatus which permits a user to create a secure network over a powerline when employing powerline modems. 
     2. Description of the Related Art 
     Powerline modems communicate by employing a power network as a transmission medium. Since modems in a plurality of locations share the power network, the shared powerline is a medium that permits a powerline modem in one house to “see” the powerline modems (and their data) at other locations, for example, other homes. Since the powerline is shared and is common to all homes data can be accessed freely over the powerline. 
     Therefore, a need exists for an apparatus and method where a user programs the same private key into all powerline modems that need to be secured. A further need exists for an apparatus and method which permits the user to program the private key into the modems without using the powerline network. This method would prevent other modems on the network from maliciously gaining access to the private key. 
     SUMMARY OF THE INVENTION 
     The present invention creates a secure powerline modem network by using a portable security device which includes a powerline modem. The security device is capable of randomly generating a number and may have the ability to let the user enter a number. This number is preferably stored in the portable security device, and the number will be a private key (y) for all of the modems on a given secured network. Each modem that needs to be secured is disconnected from the powerline modem network and then connected to the portable security device. The portable security device will provide power to the powerline modem of the device to be secured on the network, while simultaneously isolating the device&#39;s modem from the rest of the powerline modem network. 
     The portable security device then transmits the value of the private key to the other powerline modem device over their direct connection. Following this programming step, the powerline modem device is reconnected to the powerline network. Once all devices to be secured have been programmed in this manner, the master device on the network will transmit its public key (X). All powerline modems, both secured and unsecured, can hear this public key. Since all powerline modems that were programmed by the user&#39;s portable security device have the same private key, they are all able to compute a same shared key (Y) by mathematically combining the master&#39;s public key and their programmed private key (e.g., Y=(X) y ). All communication on the secured network is then encrypted using this same shared key. 
     A portable security device for setting up secure powerline modem networks is disclosed. The portable security device includes a memory which stores a protocol for communicating with powerline modem devices, and a socket configured to receive a power cord from a powerline modem device. A number assigning device transmits a private key to powerline modem devices such that the private key is stored in the powerline modem devices and is used to associate a plurality of powerline modem devices and exclude unauthorized powerline modem devices. 
     Another portable device for communicating with powerline modems includes a memory which stores a protocol for communicating with powerline modem devices. A communication link is configured to communicate with a powerline modem device such that when a communication connection is made with the powerline modem device an entire available bandwidth of the powerline modem device is available for communication. 
     A relay may be connected between the power line and the socket, which switches off power to the powerline modem device to prove that the portable device is actually connected to the powerline modem device. A filter is preferably coupled to the power line, which permits power to pass therethrough but filters out other frequencies. 
     These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     This disclosure will present in detail the following description of preferred embodiments with reference to the following figures wherein: 
     FIG. 1 is a block diagram showing a security synch device (SSD) in accordance with the present invention; and 
     FIG. 2 is a block diagram showing a system/method for securing a powerline network in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention provides an apparatus and method for creating a secured powerline network. In one embodiment, powerline modem networks can be secured by the use of cryptographic algorithms known as ciphers. A cipher is a reversible mathematical algorithm that modifies the original input data. The output of the cipher is the “secured” version of the data and it is known as ciphertext. Most modern ciphers require the use of a number known as a key. This key may be a very large number, and the key acts as the seed for the cipher. That is, encrypting the same data with the same cipher but with different keys results in completely different ciphertext outputs. The intended recipient of the data will have knowledge of the key and can decrypt the data to restore it to its original form. Unintended recipients will not have knowledge of the key and it will ideally take them an enormous amount of time to try and decrypt the data by trying all possible key combinations. 
     The level of security in the system of the present invention may be scaled based on the size of the key. Small keys make the encryption/decryption process easier, but the security is weaker. Larger keys provide more security at the expense of encryption/decryption complexity. 
     In many practical applications, the type of cipher being used, as well as the details of the cipher itself, is known (e.g., provided on a data sheet). The security of such a system depends on keeping the value of the key secret since anyone who obtains knowledge of the key could decrypt the data. 
     Setting up a secure powerline modem network provides that each modem to be secured has knowledge of an agreed-upon key. Only those modems on the secured network will have knowledge of the key and this key can be used to encrypt all data transmitted among the secure modems. By keeping the value of this key secret, a secure powerline modem network can be implemented. However, secure communication is not possible until all intended modems have knowledge of the key. Until the modems know the key value, the modems can only communicate in an unsecured mode and any data transmitted in such a mode is susceptible to unintended interception. 
     One difficulty in setting up a secured network is determining a method for informing all modems of the value of the key. A unique ID may be imprinted on each modem when it is manufactured. The user sets up a secure network by typing in the IDs of all modems to be secured into a computer with a powerline modem. This modem will be the master of the network and the master modem knows the IDs of all of the modems that will be on the secure network. It can then communicate with those modems to establish a key to be used for secure communications. A number of methods exist for setting up such a key, for example, a public key agreement scheme such as Diffie-Hellman may be employed. 
     The public key agreement technique may work as follows. The powerline modem that is the master of the network broadcasts a value known as a public key and all the modems on the network (whose IDs have been programmed into the master) will respond with their own public keys. Any modem on the network, including devices belonging to other users, can receive the public keys. The devices that the user wishes to secure will mathematically combine the public key with their own private key. The private key is stored internally in each modem and its value is kept secret. By using well-known cryptographic techniques, the combination of the public key and the private key will allow each modem to agree on a shared key that is known only by the master and the respective modem. This shared key can be used to encrypt all data transmitted between the two devices. Using the same private key for all modems immediately gives each modem on the secured network the ability to communicate securely with any other secured modem since they would all compute the same shared key. 
     It is cumbersome for the user to type in the ID numbers for each modem on the network. These numbers would tend to be long and it may not be possible for the user to bring the device near the computer. For example, if the modem is included in a television or stereo, the user would have to write down the ID code, and then enter it into a computer, which controls the network. This only works if there is a computer on the network. It will not work for networks that do not have data entry devices such as keyboards. For example, this technique will not work for a network including only a stereo and networked speakers or multiple phones or a television and DVD player. There is also the possibility that a hacker will eavesdrop on the network and obtain the IDs of other modems. The hacker could then use the ID of another modem in an attempt to appear as one of the modems on the secure network. 
     The master device would need to use a different shared key for each modem since every modem on the network would have a different private key. For the modems to be able to communicate with modems other than the master, a new shared key would need to be agreed upon by all modems on the network. 
     The present invention provides an apparatus which provides security for a powerline modem system. In one embodiment, the apparatus include a security synch device (SSD) which randomly generates a number or permits a user to enter a number. This number is a unique identification number which identifies a powerline modem or a plurality of powerline modem systems (e.g., modems at a same location). One or more powerline modems or powerline modem enabled devices (PMEDs) are each connected directly to the SSD which sends or assigns this number to the modem device. Each device at a single location may include the same number as other devices at that location or a single location may include multiple numbers. Using the assigned number, mathematically encrypted messages can be sent such that only modems on the same network or modems having a predetermined type can communicate with each other. The present invention also provides a plurality of ways of proving to the powerline modems that the SSD is located near the powerline modem instead of the signal coming from a malicious user&#39;s location. 
     For modems having a unique identification (ID) number or key, a user enters these ID numbers into a computer with a powerline modem which is the master of the network. The computer knows that only the modems with the IDs that have been entered belong to its network, and it can encrypt its data for those modems. However, the user has to type in a number for each modem and also the network needs a personal computer to enter these numbers. Powerline modem networks may include only a stereo and speaker, or two phones, or a TV and VCR, etc., where no personal computer is present, and thus there is no way to enter these numbers into the network master modem. In addition, an unauthorized user can listen to the network to hear the IDs being broadcast and then pretend to be one of those modems by using another modem&#39;s ID. 
     Referring now in specific detail to the drawings in which like reference numerals identify similar or identical elements throughout the several views, and initially to FIG. 1, a security synch device (SSD)  10  is shown in accordance with one embodiment of the present invention. SSD  10  may include a box or other shape, which is preferably small in size (portable) and inexpensive. SSD  10  includes a power plug/cord  13  (to get power from the wall outlet) and a power socket  14  (to plug a powerline-modem-enabled device (PMED) into the SSD). SSD  10  includes a random number generator  12  which can generate a random number for use as a unique ID. SSD  10  may also include a keypad or other input device  16  to permit the user to enter a number for use as the unique ID. SSD  10  includes a memory device  18  for storing the ID numbers generated or entered. Memory device  18  may further include a protocol(s)  19  for communicating with PMEDs and an operating system for controlling system functions and interactions with a user. The protocols stored therein may be any protocol known in the art, for example, TCP. SSD  10  may also include other circuitry  20  such as a processor or other devices which perform other operations such as power distribution, data transfer, logic circuits etc. as will be described herein. 
     To create a secure network, the user will take SSD  10  around to each PMED  22  and plug or otherwise connect the PMED  22  into SSD  10  using a power plug  23  which normally is used to power device  22 . Socket  14  is adapted to receive plug  23  and interface with PMED  22  in isolation from other devices. In one embodiment, a button or other mechanism  24  on the PMED  22  will be pushed to initiate a synch procedure. SSD  10  will transmit, for example, a low bit rate (so an inexpensive modem can be used in the SSD) number which may be randomly generated by SSD  10  or input by a user at input  16  to the PMED  22 . The length of the number may be selected by the user to determine the level of security. The user will repeat this process for each PMED in the home or at the given location which will be permitted to share access of the same data. The synch procedure may only need to be done at the time of purchase of a PMED or when a new network is set up (say, a subnetwork in a home). Advantageously, the PMED being set up is isolated from the powerline network during this synchronization process. SSD includes a filter  28  which permits power to pass through and filters out all other frequencies (e.g., eliminates any data transfer). Thus, no other devices can hear this transaction. 
     Once this procedure is complete, all devices in a user&#39;s home will be loaded with the same number (or multiple numbers if subnetworks are employed). Other devices outside of the network will have a different number (or none at all). In this way, access devices with a common ID can communicate to the exclusion of other devices (for example, devices at other locations). 
     Referring to FIG. 2, in accordance with one embodiment, the procedure to set up a secure network is as follows. After PMED devices  22  on a network  30  negotiate, one device  32  becomes a master of the network. Assume that the number from the SSD  10  (FIG. 1) is y, a private key, and this number will be fixed for a duration on the network  30  (e.g., months or longer). The master  32  will select a number x and only the master will know this number x can be a randomly generated private key, generated by the master. The master is also programmed with y from SSD  10 . The devices will be programmed at the factory with two numbers, g and n. The master  32  will compute a public key, for example, X=g x  mod n. Note that this is equivalent to exponentiation over a Galois (or finite) field of size n. Although this operation is easy to do, it is very difficult to compute x from X based on the mathematical fact that it is difficult to take logarithms over finite fields. Other computations and equations may also be employed. 
     In this example, the master  32  sends X out over the powerline network  30 , and all devices (the user&#39;s  22  and devices  34  outside the network) can “hear” X. The master  32  also requests that each modem on the network respond with their unique ID number after encrypting the request message (and all others that follow) with a shared key, for example, Y=(g x ) y  mod n=(X) y  mod n. The modems for devices  22  will have received X=g x  from the master  32 , and they know y from the SSD  10 . In FIG. 2, y is downloaded to devices  22  as described above with reference to FIG. 1, connections between SSD  10  and devices  22  are illustratively shown to indicate the origin of y. The master  32  will be able to decrypt the message since x is chosen by master  32  and the master  32  knows y from the SSD  10 . Any messages sent by the other modems (devices  34 ) from a different network will not know y, and the master  32  will realize that the devices  34  are not on the same network. Thus, a network of PMEDs is secured without mistakenly including (or allowing a hacker to insert) other modems. 
     Other embodiments may include simpler or more complex security schemes. For example, after each device  22  is assigned a private key y. Master  32  generates a public key X and sends X to devices  22 . A shared key Y is computed based on X and y at each device. (for example Y=(X) y ). Y is then employed for encrypted communications within the secured network. 
     Referring again to FIG. 1, instead of pushing a mechanical mechanism  24  to initiate synch (which needs a small button to be added to the PMED or SSD), there are other methods for initiating the synch process. The goal is for the PMED to be sure that the random number y is really coming from its owner&#39;s SSD  10 , and not an unauthorized user&#39;s SSD or modem. Button  24  provides a way to prove that the SSD  10  is directly connected to the PMED (and not connected via the powerline from an unauthorized user&#39;s location). Making a user perform an overt act, e.g., to push a button on the PMED is one way of ensuring that the PMED is set up properly. A direct connection between SSD  10  and the device  22  may include a wireless radio frequency or infrared link. Instead of plug  23  and sockets  14 , antennae are employed. 
     In another embodiment, a relay  40  may be provided in SSD  10 . In this alternate embodiment, since the PMED will be receiving its power from the SSD  10 , the SSD  10  can initiate a shutdown sequence of the PMED to prove that it is actually connected to the PMED. The PMED would then load the random number after the SSD turns power back on. 
     SSD  10  controls relay  40 , which may be used to switch off the PMED and then switch the PMED back on. This proves to the PMED that the PMED is connected directly to SSD  10  and is not being connected to an unauthorized user. SSD  10  may be employed for other uses as well. For example, SSD  10  may be employed to directly connect to a powerline modem enabled device using a full bandwidth of the modem (instead of sharing bandwidth with other devices on the powerline network). In addition, using the full bandwidth avoids impairments on a main powerline network. These advantages may be employed to, for example, quickly download audio, video, computer programs or other data onto a device. In one embodiment, software in a device  22  may be updated (e.g., user programs or device drivers) by downloading data or programs from memory  18  onto a device  22 . 
     Having described preferred embodiments for an apparatus for providing security on a powerline-modem network (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art in light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments of the invention disclosed which are within the scope and spirit of the invention as outlined by the appended claims. Having thus described the invention with the details and particularity required by the patent laws, what is claimed and desired protected by Letters Patent is set forth in the appended claims.