SUPPLY SYSTEM

Abstract: A system for supplying pre-paid goods or services eg electricity to a user, comprising: a monitoring device locate at the user's premises for monitoring usage of goods or services, the device including a storage means for storing a signal indicative of the current amount of credit, a keyboard for entering an encoded message in the form of a data encryption standard code which includes information indicative of an amount of credit, decryption means for decrypting the encoded message, and processing means for processing the decoded message in order to determine the amount of credit and for updating the storage means; and a message generating device located remote from the user's premises for generating an encoded message in the form of a data encryption standard code in a discernable alpha-numeric format, the encoded message generating device and the decryption means utilising the same key, which key is changed for every transaction.

Description: SUPPLY SYSTEM The present invention relates to the supply of goods and/or services. More particularly, the present invention relates to the supply of utilities such as gas, electricity, water, heat or cable television. In view of the fact that the primary use of the present invention is for the supply of gas or electricity the following description will be based on this use. However, it is to be understood that the invention is of more general application and could apply to other goods or services. The supply of gas or electricity is conventionally monitored by a meter. Traditionally, meters were either simply an accumulation of the amount of gas or electricity used which required the meter to be read periodically so that the customer could be billed or else the meter was a coin released device. However, coin released devices were susceptible to damage by thieves stealing the coins and consequently, more recently, it has become common to have a pre-payment meter which required the entry of information into the meter rather than the insertion of a coin to supply the electricity. One way of achieving this was for the customer to go to a central location and purchase a "key" which could be inserted in the meter and thereby supply a measured quantity of electricity. EP-A-0420466 proposed an alternative to this basic principle by providing a meter with a keypad and arranging for the customer to be given a discernable alpha-numeric code in exchange for handing over cash at a central location. The code supplied to the customer is based on the identification number of the electricity meter concerned and the amount of money which has been handed over by the customer. The problem with this arrangement is that it is not secure and is limited in the amount of information it can carry. It would be relatively easy for a customer to determine the coding scheme utilized in view of the fact that the meter identification is an unvarying number and also the customer determines the amount of money which is also being used as part of the coding process. It is an object of the present invention to provide a system which is much more secure than the above-described prior arrangements but which still enables the customer to simply key-in a code preferably in the form of a discemable alpha-numeric sequence. The present invention is based on the encoding means and the decoding means at the user's premises utilizing the same key, which key is changed for every transaction. Preferably, the plain text message is in the form of a data encryption ' standard code which can be "read" by the meter and checked for accuracy by appropriate signal processing. In order that the present invention be more readily understood, an embodiment thereof will now be described by way of example with reference to the accompanying drawings in which: Fig 1 shows schematically a system according to the present invention; and Fig 2 is a diagrammatic representation of message according to the present invention. The present invention is based on the Calmu technology which has been utilized by the applicants for many years and which includes, inter alia, an electricity meter provided with a keypad and display. It has previously been proposed to supply information to a Calmu meter utilising the electricity supply cables themselves in such a way that each meter can be addressed individually up to 40 times a week. This was proposed in order to provide credit and load-limiting facilities and avoid the need to physically read meters or send information from the meter itself back to a central station. While this system was technically good, an alternative was to get customers to actively participate in the operation by entering data which would credit the meter with an appropriate amount of money in order to continue supply of electricity and we have therefore devised a secure way in which to carry this out. In view of the fact that customers are prepared to leave their homes and go to central locations and purchase "keys" as mentioned before, we have decided to utilize a somewhat similar system in that the customer will still attend at a central location, hand over cash or utilize a credit card or some other payment system and be supplied with a code which can be entered into the meter utilising the keypad. In our system, there is no need for the customer to attend a vending location but for the purposes of the present description we will assume that the customer does indeed attend a vending location 10 where he identifies himself and hands over a sum of money. Information relating to the customer and also the sum of money tendered is fed into a processing machine 11 which is utilized to interrogate a remote computer and database 12 where account history details relating to the tariff of the user, the utility type, ie electricity or gas and the source of the utility, ie the electricity retail company with which the customer is registered, are used and a plain text message is formed which is then encrypted using a key and the encrypted message transmitted back by the computer 12 to the vending location 10. In our preferred system, the encrypted message is a 20 digit alpha- numeric code which is printed out on a slip of paper which is then handed to the customer for him to enter into his meter 21 using the keypad 22 associated therewith. The key utilized to encrypt the plain text message is changed with every transaction so that each plain text message is encrypted using the latest key in a key sequence. Each meter is provided with a key sequence and only a meter utilizing the appropriate key can decrypt the message and utilize the part of the message indicative of the amount of money which in turn is indicative of the amount of electricity which should be permitted to be used. In view of the fact that there is no fixed information which is repeated time after time in respect of the same meter, the above-described system is extremely secure. The key utilized by the central computer 12 to encrypt the plain text message must be the same as that used by the meter 21 to decode the message. This can be achieved in a number of ways depending upon the degree of security required. Basically, one is seeking to ensure that the same 20 digit encoded message cannot be used again by the same meter nor be applied to another meter in order to provide credit to that other meter. One way of synchronising the keys is for the central computer and the meter to utilize the same algorithm for generating keys and "seeding" the algorithms with the same start key, for example depending on the number of times the meter has been incremented with cash payments. The central computer will know this as also will the meter without there being any need to signal this in the plain text message. Such a method means that the same coded text message will not result in a proper decode by the same meter because the meter will move to the next key which is different to that used to produce the plain text message. Also, it is unlikely that even a different meter with the same algorithm will be in the same position in the sequence determined by the algorithm as the meter in which the message was used originally, again resulting in an improper decode. The correctness of the decode can be checked in any one of a number of different ways, eg a check digit or sequence. It is thus not necessary to have each meter uniquely identified nor use any recurring information such as an identification number in the message. The decoded message has a defined structure and this will now be described in relation to Figure 2 which shows the preferred form of the message. The preferred form of message is a 20 digit number each number being a decimal number of 0 to 9. The underlying message is in fact a data encryption standard code which in this example is a 64 bit code formed as two blocks of 32 bits. Figure 2 is a diagrammatic representation of the information which will be contained in the encoded message and is not intended to indicate which particular digits represent information relating to specific parts of the original 64 bit message. As shown in Figure 2, the 20 digit message contains control bits, information relating to the utility being metered, the source of the utility, the amount of money being credited, the tariff and also authentication bits. Once decoded, the appropriate bits of the original plain text message appear in predefined positions within the message and consequently the meter will go through a logical checking sequence after decoding a message to ensure that the decoding has resulted in the correct locations receiving appropriate information. One way of achieving this is to have an account sequence number included in the authentication portion of the message which can be checked against previous account sequence numbers temporarily stored in the meter and overwritten when a correct decode is signalled. A modification to the above basic structure will now be described and this is based on the transfer of more information to the meter, utilising a plurality of encoded messages. The transfer may be achieved in any one of a number of ways. For example, a plurality of 20 digit alpha-numeric sequences can be used with the first sequence signalling to the meter that additional sequences follow. An alternative is to make the sequence of variable length and signal the length in the sequence. In this example, it is assumed that each encoded message is a 20 digit alpha-numeric sequence and in this case the first 20 digit sequence is used to signal to the meter that one or more additional 20 digit sequences are to be expected. This ability to signal that additional information is to be expected can readily be achieved since a 20 digit code with each digit being a decimal number between 0 and 9 inclusive is 5.2 times too big for the DES code hence there are two bits redundant in the 20 digit code. One or both of these redundant bits can be used to signal the presence of an additional encoded 20 digit message or messages. In one particularly preferable solution, the 64 bit DES code is divided into two blocks of 32 bits. The first number in decimal of each group is used as the redundant bit and it is determined that if the decimal value of this bit is less than 5 if encoded directly, then this signals that additional information is present. It is therefore proposed to add 5 (or not) to each of these decimal values in order to carry an un-encoded message with four possible values (00, 01, 10, 11). One of these values (eg 11) is used to indicate that there is another message expected. One of the other logic values could be used to identify that the message is for another utility which would be vital when a different key is essential for each utility, and this must be known before attempting a decode. With the above scheme, before decoding the 20 digit number, the tenth and twentieth digit is examined and if greater than 5, the appropriate flags are set and the value of the tenth and twentieth digit has 5 deducted from it. In this scheme, if the continuity flag is set to the value 1 1, then upon decoding, the amount section of the code is used to indicate a tariff change and not a credit transfer. The scheme then requires another 20 decimal digit message to be received in order to indicate the amount of credit transferred at the new rate which is indicated by the tariff code portion of the second 20 digit message. If the 20 digit messages are entered in the wrong order, the credit transfer block will not be valid since it will be carrying the wrong tariff code. The credit transfer block does not carry any extra bits if it is for an electricity account. The customer then has to enter the tariff change block before he can enter a valid credit transfer block. When more than one 20 digit message is being transferred, it should be remembered that each 20 digit block actually represents a 64 bit message. In these circumstances, it is possible to split the two 64 bit messages in half and send the two first halves in one message and the two last halves in the second message. This requires the meter to store and then reassemble the received half messages into two complete 64 bit messages before decoding. This additional complexity results in a greater degree of security. As indicated above, while it is preferable for the customer to attend a vending location, it is also possible to provide the encrypted message to the customer in other ways, eg by telephone, via the Internet or interactive television.

Claims: CLAIMS 1. A system for supplying pre-paid goods or services to a user, comprising: a monitoring device located at the user's premises for monitoring usage of goods or services, the device including a storage means for storing a signal indicative of the current amount of credit, a keyboard for entering an encoded message which includes information indicative of an amount of credit, decryption means for decrypting the encoded message, and processing means for processing the decoded message in order to determine the amount of credit and for updating the storage means; and a message generating device located remote from the user's premises for generating an encoded message in a discemable alpha-numeric format, characterised in that the encoded message generating device and the decryption means utilize the same key, which key is changed for every transaction. 2. A system according to claim 1 , wherein the encoded message represents a data encryption standard code. 3. A system according to claim 1 or 2, wherein the encoded message includes information indicating extended information. 4. A system according to claim 3, wherein the extended information is in the form of one or more additional encoded messages each of a defined length. 5. A system according to any one of the preceding claims, wherein the encoded message generating means includes means for accessing the account history of the user. 6. A system according to claim 5, wherein the account history of the user is utilized to determine the key used to encode the message. 7. A system for supplying pre-paid goods or services to a user substantially as hereinbefore described with reference to the accompanying drawings.

Inventors: FIELDEN JOHN, JAMES ANDREW, SINGHAL SANJAYA, FIELDEN, JOHN, JAMES, ANDREW, SINGHAL, SANJAYA
Applicants: FIELDEN JOHN, JAMES ANDREW, PRI LTD, SINGHAL SANJAYA, FIELDEN, JOHN, JAMES, ANDREW, PRI LIMITED, SINGHAL, SANJAYA
Application year: 2001
Main classification: G07F15
IPC codes: G07F7, G07F15