GB2460653A

GB2460653A - Encryption using synchronisation

Info

Publication number: GB2460653A
Application number: GB0810102A
Authority: GB
Inventors: Davide Antilli
Original assignee: DMK IO Ltd
Current assignee: DMK IO Ltd
Priority date: 2008-06-03
Filing date: 2008-06-03
Publication date: 2009-12-09
Also published as: GB0810102D0

Abstract

In a secure data transmission system, data is encrypted by a value 50 read by a synchronised clock 35 after start and stop signals are sent from a transmitter 20. After transmitting a list of numbers (perhaps itself in the form of time intervals), sending clock 25 is started and a stop signal sent when the sending clock reaches a value matching a predetermined random number key, with the receiving clock being resynchronised at regular intervals. An optimal counting rate is set by control signals from a controller 38 according to channel parameters, and the rate is reduced as the value approaches to prevent overshoot. Eavesdropping third parties thus cannot acquire the encrypting value.

Description

Method and Apparatus for the transmission of an item of data to a receiver

Description

Title of the Invention

[0001] Method and Apparatus for the transmission of an item of data to a receiver

Cross Reference to Related Applications

[0002] None

Field of the Invention

[0003] The application relates to an apparatus and method for the transmission of a pre-determined value and to an apparatus and method for the transmission of a sequence of predetermined data.

Background to the Invention

[0004] Apparatuses for the transmission of pre-determined values are known in the art. Such apparatuses can transmit the pre-determined value from the sender to a receiver. This can require substantial bandwidth on the data transmission channel to transfer the data.

Furthermore, the data is often transferred in an open manner which could be intercepted by a third party who should not read the pre-determined value.

[0005] Methods have been developed to compress data in order to reduce the amount of data that should be transferred and/or encrypt the data in order to ensure that it is not read by an inquisitive third party.

[0006] Methods for encrypting data include data encryption standards such as the RSA algorithm, disclosed in US Patent 4,405,289.

[0007] Methods for the compression of data are also known in the art. For example, one of the patents which is included in the MPEG-3 standard (otherwise known as MP3) is PCT Application Nr. WO 88/01811.

[0008] Using the above mentioned methods, however, compression of random strings of numbers is, however, not possible.

[0009] Summary of the Invention

[00010] The object of the invention is therefore to improve the method and apparatus for transmitting a pre-determined number in the form of an item of data from a sender to a receiver.

[00011] A further object of the invention is to provide a method and apparatus for efficiently transmitting a random number from a sender to a receiver.

[00012] A further object of the invention is to reduce the amount of bandwidth required on a data transmission channel to transmit the item of data from a sender to a receiver.

[00013] Still a further object of the invention is to provide a secure method and apparatus of transmitting a pre-determined item of data from a sender to a receiver.

[00014] These and other objects of the invention are solved by providing a method comprising the steps of synchronising a sender clock at the sender with a receiver clock at the receiver; sending from the sender to the receiver a start signal; waiting until the sender clock has reached a value matching the item of data; sending a stop signal from the sender to the receiver; and reading the value of the item of data from the receiver clock.

[00015] Using this method, the value corresponding to the item of data is never transmitted directly between the sender and the receiver. Instead only a start signal and a stop signal are transmitted. As a result, the amount of bandwidth used is substantially reduced.

Furthermore, it is not possible for a third party to intercept a data signal and thus determine the value of the transmitted item of data.

[00016] Tn a further aspect of the invention, the method includes a step of re-synchronising the sender clock with the receiver clock at regular intervals. This is to ensure that the value read out at the receiver clock is accurate.

[00017] It is possible for the sender clock and the receiver clock to have variable counting rates. In this case the sender must ensure that the stop signal is sent at a time point which takes into account the variable counting rate.

[00018] Tn order to ensure that an accurate value matching the item of data is transmitted, it might prove useful to reduce the counting rates of the sender clock and the receiver clock as the order of magnitude of the value matching the item of data is approached.

This ensures that the receiver clock cannot "overshoot" the value equating to the item of data and thus give an inaccurate reading.

[00019] Tn order to improve the representation of the item of data, an exchange of control values between the sender and the receiver takes place to determine an optimum counting rate for the sender clock. The specific physical conditions of any given communications channel, notably the variation in signal propagation speed between sender and receiver, will limit the maximum effective clock speed or Sender Frequency'. For example, the clocks might be capable of measuring intervals to within 1012 seconds, but if the transmitted signals were found to reach the sender with an unpredictable delay of +1-10b0 seconds, data could not be accurately represented unless the clock speed were accordingly reduced. Critical factors include, but are not limited to, delay spread', atmospheric conditions, other noisy' effects, and relativistic effects, all of which are well known to those skilled in the Art.

[00020] Advantageously, the method also includes the transmission of control values to verify that speeds of the sender clock and the receiver clock match. This ensures that the time measurement of both the sender clock and the receiver clock is accurate.

[00021] The time interval may also be derived by any other physical analysis, whereby a time lapse between the start signal and stop signals may be derived. Indeed, a time lapse may be calculated in other ways rather than a direct time measurement method of a clock. For example, the time lapse can be measured by wave analysis, where a distance to time conversion may be used for expressing an time interval between two data signals, starting from the overlay between data signals.

[00022] A method for the transmission of a sequence of a given number of items of data from a sender to a receiver is also disclosed. The method preferably comprises sending a first item of data from the sender to the receiver, wherein the first item of data is transmitted as a first data signal, and sending a second item of data using a transmission method, comprising the steps of synchronising a sender clock at the sender with a receiver clock at the receiver; sending from the sender to the receiver a start signal; waiting until the sender clock has reached a value matching the first item of data; sending a stop signal from the sender to the receiver; and reading the value of the first item data from the receiver clock. These steps of sending a first item of data as a data signal and of sending a second item of data as a time interval between the start and the stop data signals, with the above transmission method are repeated until the given number of items of data has been transmitted.

[00023] A method wherein items of data are sequentially sent using a known transmission method is therefore disclosed. The items of data are transmitted as data signals embodying a value representing the item of data, either directly as a symbolic value or as a time interval.

[00024] Advantageously, some of the items of data are transmitted directly between the sender and the receiver while some of the items of data are never transmitted directly.

[00025] Tn a further aspect, the item of data is comprised of odd-numbered items of data and of even-numbered items of data. The odd-numbered items of data are transmitted as corresponding odd-numbered data signals, wherein the corresponding odd-numbered data signals at the receiver acts as the start signal for the transmission of following even-numbered items of data.

[00026] Tn a further aspect, the items of data are comprised of odd-numbered items of data and of even-numbered items of data. The odd-numbered items of data are transmitted as corresponding odd-numbered data signals, wherein the corresponding odd-numbered data signals at the receiver acts as the stop signal for the transmission of preceding even-numbered predetermined data.

[00027] A method is also disclosed wherein the data strings are sequentially sent in alternation as signals having a symbolic value representing the predetermined number, and values expressed as intervals or interstices between start/stop signals, i.e. between signals proper.

[00028] Additionally, using this method may help increase data throughput over a channel. In particular, the transmission of a sequence of a given number of items of data from the sender to the receiver comprising a known method of sending directly each item of data as a data signal, such as wavelength, may require a large amount of bandwidth. On the other hand, the time required to transmit successive items of data using the method of transmitting a sequence of items of data uniquely as intervals between two transmitted data signals will increase exponentially with the size of the predetermined data. The inventive method may advantageously take advantage of the two methods, namely with less bandwidth consumption, and without overrunning the efficiency threshold of the interval method of expressing data values, i.e. the point beyond which it becomes more efficient to express a value as a transmitted data signal rather than as a interval increment, the efficiency of which latter method decreasing exponentially over time.

[00029] In a further aspect, a method for the transmission of a data string is disclosed.

The method comprises the steps of dividing the string into substrings, parsing each substring to determine a substring value representative of data of each substring, obtaining a sequence of numbers corresponding to the substring values of each substring, sending the sequence using the inventive hybrid method for transmitting a sequence of data as described above.

[00030] These and other objects of the invention are also solved by an apparatus with a sender having a sender clock and a receiver having a receiver clock. The sender clock counts to a pre-determined data and ensure that a start signal is transmitted when the sender clock starts counting to the value of the item of data and a stop signal is transmitted when the value of the item of data is reached.

[00031] The receiver has a receiver clock for counting to a value. The receiver clock starts counting on receipt of the start signal from the sender and stops counting on receipt of the stop signal from the sender. Thereafter the value of the item of data can be read out on the receiver clock.

[00032] As discussed above, it is useful to synchronise the sender clock and the receiver clock and with this in mind, the sender is provided with a sender synchronisation module for the transmission of synchronisation signals and the receiver is provided with a receiver synchronisation modules for the receipt of the synchronisation signals.

[00033] Advantageously, the apparatus may be provided with a control transmission to verify that the speeds of the sender clock and the receiver are set at an optimum permissible value given the physical condition of the communications channel, and that they match. This helps to ensure the accuracy of the time interval measurements.

[00034] The receiver may also be provided with means for deriving a time interval is based on other physical analysis, whereby the time lapse between the symbolic start signal and stop signal may be derived, such as wave analysis, in particular overlay between two data signals, the overlay being then converted for expressing an interstice between two data signals.

Description of the Drawings

Fig. 1 shows an example of a transmission and receiver apparatus according to one aspect of this invention.

Fig. 2 shows a flow diagram of a method for the transmission of a data.

Fig. 3a shows a sequence of data and fig. 3b shows a flow diagram of a method for the transmission of the sequence of Fig. 3a.

Fig. 4a shows a flow diagram of a method for the transmission of a data string, and Fig. 4b shows the data string to be transmitted in Fig 4a.

Detailed Description of the Invention

[00035] For a complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the figures.

[000361 It should be appreciated that the aspects of the invention discussed herein are merely illustrative of specific ways to make and use the invention, and do not therefore limit the scope of the invention when taken into consideration with the claims and the following detailed description including the examples of the present invention. In particular it should be noted that the features found in aspects of the present invention can be combined with features for other aspects of the invention [00037] Fig. 1 shows an apparatus 10 for the transmission of a value from a sender 20 to a receiver 30 using a signal 40 over a data transmission channel. The data transmission channel can be, but is not limited to, a copper cable, an optical fibre, or wireless transmission.

The sender 20 has a sender counter 25 which counts at a sender frequency Sf. The receiver 30 has a receiver counter 35 which counts at a receiver frequency Rf. The sender counter 25 and the receiver counter 35 are preferably identical and preferably the sender frequency Sf and the receiver frequency Rf are the same. The sender clock 25 and the receiver clock 35 are provided however with synchronisation means 37 to enable them to synchronise their values if required. Additionally, a control module 38 sends control values to allow the receiver 30 to determine the optimum speed of the sender clock 25, and, further, to verify that the speed of the sender clock 35 and the speed of the receiver clock 35 match.

[00038] The apparatus 10 is further provided with physical analysis device ananged to derive by physical analysis of the data signals a time interval between the start data signal and the stop data signal. In particular, wavelength analysis on the stop data signals and the start data signals can be performed to determine the time interval between the start data signal and the stop data signal.

[00039] The method for transmitting the pre-determined value is shown in Fig. 2. In a first step 100, the sender counter 25 is synchronised with the receiver counter 35. This is achieved by sending a series of test values from a sender synchronisation module 27 as a data signal 40 on the data transmission line from the sender 20 to the receiver 30. The receiver 30 receives the test values as data signals 40 at a receiver synchronisation module 37 and is able to calculate the transmission delay Td from the sender 20 to the receiver 30 and if necessary to modify the optimum sender frequency Sf.

[000401 Tn order to transmit the data, the sender 20 sends in step 110 a data signal 40 to the receiver 30 telling the receiver counter 35 to start counting (step 120). The sender counter is started at the same time. After the sender counter 25 has reached the predetermined value which should be transmitted to the receiver 30, the sender 20 sends a further data signal 40 (step 130) to the receiver 30 to stop the receiver counter 35 from counting (step 140). The sender 20 knows the receiver frequency Rf and the transmission delay Td. It is able to calculate in step 150 the value that the receiver clock 35 has when the data signal 40 indicating stop counting is received. The receiver 35 is able to read this value from the receiver clock 35 and the value has been transmitted. This value can thus be transmitted more efficiently. The value is output on an output device 50 such as a printer or visual display unit.

[00041] Tn a further aspect of the invention, the rate at which the receiver counter 35 and the sender counter 25 are running can be reduced as the sender counter approaches the value to be transmitted. This is done by sending a signal from the sender 20 to the receiver 30 to slow down the rate of counting.

[00042] Tn yet a further aspect of the invention, the sender 20 and the receiver 30 can initiate a dialogue as they approach the value to be transmitted in order to ensure that the sender clock 25 and the receiver clock 35 are in exact synchronisation. This could include sending data signals 40 to instruct the receiver clock 35 to stop, count forward, count backward or count slowly.

[00043] Fig. 3a shows a sequence 42 comprising three items 43, 44 and 45 of numerical data. Fig. 3b shows the method for transmitting the sequence 42.In a first step 1000, the sender counter 25 is synchronised with the receiver counter 35. This synchronisation is achieved by sending a series of test values from a sender synchronisation module 27 as a data signal 40 on the data transmission line from the sender 20 to the receiver 30. The receiver 30 receives the test values as data signals 40 at a receiver synchronisation module 37 and at a control module 38 and is able to calculate the transmission delay Td from the sender 20 to the receiver 30 and to determine the optimum sender frequency Sf by analysing local effects such as the delay spread.

[00044] The first item of data 43 is sent by the sender 20 in step 210 as a first data signal to the receiver 30. The first data signal acts as a start signal telling the receiver counter to start counting, at the step 220. The sender counter 25 is started at the same time. After the sender counter 25 has reached the value corresponding to the second item of data 44 which should be transmitted to the receiver 30, the sender 20 sends a third data signal (step 230) corresponding to the third item of data 45 to the receiver 30. This third data signal data acts as the stop signal telling the receiver counter 35 to stop counting (step 240).

[00045] The sender 20 knows the receiver frequency Rf and the transmission delay Td.

The sender 20 is able to calculate in step 250 the value that the receiver clock 35 has when the third data signal indicating stop counting is received. The receiver 35 is able to read this value from the receiver clock 35 and the value has been transmitted. This value conesponds to the value matching the second transmitted item of data 44.

[00046] The receiver 35 measures the transmitted data signals and can derive the value of the first and third item of data 43, 45 (step 260).

[00047] The sequence 42 is obtained and the values of the items of data are output on the output device 50 (step 270).

[00048] In other words, the second item of data is sent as a measured interval.

[00049] Hence, the sequence of data items is sent using a hybrid method wherein the sequence of data items are sent in alternation as signals having a symbolic value representing the predetermined number, and values expressed as time intervals or interstices between the data signals. Advantageously, the time lapse value of the time interval is independent of the start and stop data signals demarcating the time interval, while the symbolic values of the data signals, for instance wavelength, is independent of the time of its arrival.

[00050] Fig. 4a shows the method for the transmission of a data string 46 and Fig 4b shows the data string 46 at different steps of the transmission method. In a first step 310, the data string 46 can be divided into a given number of data substrings 47, 48, 49, 50, 51, 52, 53.

The odd-numbered substrings 47, 49, 51, etc, in the substring sequence are parsed and their symbolic values 47a, 49a, S la, etc, (e.g., wavelengths) are found. The even-numbered substrings 48, 50, etc, are parsed and are implemented as an interval value 48a, SOa, 52a representative of the data substring, at step 320. The substrings transmitted as symbolic values (eg wavelengths) need not be the same length as those expressed as time intervals. A sequence of seven substring values 47a, 48a, 49a, 50a, 5 la, 52a, 53a, conesponding to the seven data substrings 47, 48, 49, 50, 51, 52, 53, is thus obtained at step 330. The sequence of data substring values is sent using the above method described with reference to Fig. 3 at step 340. More precisely, the first string value 47a is sent as a first data signal to the receiver 30 and acts as the start signal telling the receiver counter 35 to start counting. The sender counter is started at the same time. After the sender counter 25 has reached the second one of the substring values, i.e. the interval value 48a, the sender 20 sends the third data signal corresponding to the third substring value 49a. The third data signal acts as the stop signal for the transmission of the substring value 48a telling the receiver 30 to stop counting.

Additionally, the third data signal also acts as the start signal for the transmission of the next substring value 50a, and so on. The seven values are thus transmitted as an alternate series of symbols and of measured time intervals, in this example five symbols and four time intervals.

[00051] At the receiver, the transmitted symbols 47a, 49a, Sla, 53a, are measured, and is converted back into the data substrings 47, 49, 51, 53. Additionally, the time intervals 48a, 50a, 52a, between the transmitted symbols are also measured, and converted back into the corresponding substrings 48, 50, 52. The substrings 48, 50, 52are then interlaced in order to obtain the data string 46 (step 350).

Claims

Claims 1. Method for the transmission of an item of data from a sender (20) to a receiver (30) comprising the steps of: synchronising (100) a sender clock (25) at the sender (20) with a receiver clock (35) at the receiver (30); sending (110) from the sender (20) to the receiver (30) a start signal (40); waiting until the sender clock (25) has reached a value matching the item of data; sending (130) a stop signal (40) from the sender (20) to the receiver (30); and reading (150) the value of the item of data from the receiver clock (35).
2. Method according to claim 1, further comprising a step of re-synchronising the sender clock (25) with the receiver clock (35) at regular intervals.
3. Method according to any one of claims 1 to 2, where control values are transmitted to allow the receiver (30) to determine an optimum speed of the sender clock (25) for a specific communications channel.
4. Method according to claim 1 or 3, wherein the sender clock (25) and the receiver clock (35) have variable counting rates.
5. Method according to claim 4, wherein the counting rate of the sender clock (25) and the receiver (35) clock are reduced as the value of the item of data is approached.
6. Method according to any one of the above claims, further comprising the exchange of signals between the sender (20) and the receiver (30) whilst the sender clock (25) is counting to the item of data.
7. Method according to claim 1, wherein the time interval between the stop signal (40) and the start signal (40) is calculated by physical analysis of the transmitted signals.
8. Method for the transmission of a sequence of a given number of items of data from a sender (20) to a receiver (30) comprising a) sending (210) a first item (43) of data from the sender (20) to the receiver (30), wherein the first item of data is transmitted as a first data signal, b) sending (220, 230) a second item of data (44) using a method according to any one of claims 1 to 5, c) repeating the steps (a) and (b) until the given number of items of data (45) has been transmitted.
9. Method according to claim 8, wherein the items of data (43, 44, 45) are comprised of odd-numbered items of data (43, 45) and of even-numbered items of data (44), the odd-numbered items of data (43, 45) being transmitted as corresponding odd-numbered data signals, wherein said conesponding odd-numbered data signals at the receiver (30) acts as the start signal for the transmission of following even-numbered item of data (44).
10. Method according to claim 8 or 9, wherein the items of data (43, 44, 45) are comprised of odd-numbered items of data (43, 45) and of even-numbered items of data (44), the odd-numbered items of data (43, 45) being transmitted as corresponding odd-numbered data signals, wherein said corresponding odd-numbered data signals at the receiver acts as the stop signal for the transmission of preceding even-numbered items of data (44).
11. Method for the transmission of a data string comprising the steps of dividing (310) the data string (46) into substrings (47, 48, 49, 50, 51, 52, 53) of given length, parsing (320) each one of the substrings (47, 48, 49, 50, 51, 52, 53) to determine a substring value (47a, 48a, 49a, 50a, 51a, 52a, 53a) representative of data of each one of the substrings (47, 48, 49, 50, 51, 52, 53), obtaining (330) a sequence of numbers conesponding to the substring value (47a, 48a, 49a, 50a, 51a, 52a, 53a) of each one of the substrings(47, 48, 49, 50, 51, 52, 53), sending (340) the sequence using a method according to anyone of claims 8 to 10.
12. Apparatus (10) for the transmission of an item of data to a receiver (30) comprising: a sender (20) having a sender clock (25) for counting to a value matching the item of data and for transmitting (110) a start signal (40) when the sender clock (25) starts counting to the value and a stop signal (40) when the value is reached (130); a receiver (30) having a receiver clock (35) for counting to a value, whereby the receiver clock (35) starts counting on receipt of the start signal (40) from the sender (20) and stops (140) counting on receipt of the stop signal (40) from the sender (20).
13. Apparatus according to claim 12, wherein the sender (20) further comprises a sender synchronisation module (27) for the transmission of synchronisation signals (40).
14. Apparatus according to claim 12 or claim 13 wherein the receiver (30) further comprises a receiver synchronisation module (37) for the receipt of the synchronisation signals (40).
15. Apparatus according to any one of claims 12 to 14 comprising an output means (50) at the receiver (30) for outputting the value.
16. Apparatus according to any one of claims 12 to 15, further comprising a control module (38) for ensuring that the speed of the sender clock (35) and the speed of the receiver clock (45) substantially match an optimum permissible value given physical channel conditions specific to a transmission session.
17. Apparatus according to claim 12, further comprising a physical analysis device (60) for performing physical analysis for deriving the time interval between the start signal (40) and the stop signal (40).