GB2377859A

GB2377859A - Providing a text message with a watermark

Info

Publication number: GB2377859A
Application number: GB0117640A
Authority: GB
Inventors: Simon Luttrell
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-07-19
Filing date: 2001-07-19
Publication date: 2003-01-22
Also published as: GB0117640D0

Abstract

Mobile wireless devices used for receipt of text messages can only display a defined set of alpha-numerical characters. A binary-coded sequence of spaces and line returns will not be apparent to the mobile user if this occurs at the end of the text message. Such binary-coded sequence may be used to embed an authentication code within the text message that is sent by the message generating station. This code can then be authenticated by transmitting the text message, as received on the mobile device, to an authentication station. Such mobile devices also support the entry of a defined set of alpha-numerical characters via the keypad. A text message may be sent by a message generating station which includes an alpha-character 'security icon' within the message header that is supported by the mobile device display, but is not supported by the keypad. If this message is forwarded by the intended recipient to an unauthorized second recipient, the 'security icon' will no longer be displayed in the message header. Furthermore, the second recipient will be unable to falsify this sender detail in the mobile device address book since the 'security icon' cannot be entered via the mobile device keypad. It is also possible for the message generating station to synchronise the message time-stamp with a time-stamp contained within the message body to provide a further means of message authentication that is not easily reproducible by unauthorized parties.

Description

MESSAGE SYSTEMS This invention is directed to message systems, and in particular aspects, to such systems as-employed in mobile telephony.

Simple messaging systems are used in various forms of modern communication ; a very important example being-te) messaging systems-such as the Short Message System (SMS) employed by mobile telephones and related devices.

Text messaging has proved to be a popular communication medium with two reasons for the success of the medium being the restricted size of each message and the adherence of multipieperators to a common standard such as SMS. Commercial applications are now being developped for mobile telephony which extend beyond point-to-point communication and it would be-desirable for such -applications to -take advantage of the wide usage of text-messagmg.

Most commercially directed applications will require some form of authentication or other protection against fraud or misuse. A great deal of work has of course already been undertaken within the broad field of electronic-oommerce and a wide variety of solutions exist for providing secure commercial transactions.

Within the field of mobile telephony, and particularly in the field of text messaging, the value of commercial transactions is likely to be modest, but some form of authentication will nevertheless be essential if an attractive range of commercial applications is to become available. Here, the restricted size of text-messages and the universality of the underlying protocols-which are important parts of the success of the medium-present real problems.

Secure transactions or other protections against fraud or mis-use generally involve complex encryption techniques. In text messaging, there is neither the physical space nor appropriate provision in the protocois, for such techniques, The present invention aims therefore to provide a system compatible with existing -text messaging systems for the verification of senders or

recipients or other authentication of messages.

Accordingly, the invention consists in one-aspect in a messaging system m-which text messages are transmitted wiretessiy to mobile handsets each having a display, there being a protocol for the transmission of a defined set of characters with the display of each handset being adapted to display alphanumeric characters from said set, wherein selected text messages are coded by the introduction into the text message of a code sequence-of-characters from the defined sel-which characters are not displayed-on the handset displays.

Preferably, the messaging system, comprises an authentication station adapted to read said code sequence.

Suitably, the code sequence includes the character representing a space or the character representing a return. Such code sequence is not immediateiyappare-nt on the handset display if it occurs at the end of an alpha-numeric text message.

In another aspect, the present invention consists in a messaging system in which-text messages are transmitted wirelessly to mobile handsets each having a display and a-key pad for the-entry of characters, there being a protocol for the transmission of a defined transmission set of characters with the display of each handset being adapted to display each character in 13 display sub-set of the transmission set of characters and with the key pad of each handset being adapted to enter only characters from a key pad sub-set of the transmission set of characters, wherein selected text messages are authenticated at an authenticated message generation station by the introduction into the text message of a one or more authentication characters which form part of the display sub-set but which do not form part of the key pad sub-set.

Advantageously, each text message contains a section which is automatically generated on transmission of the message by a handset message generation station being adapted to introduce the or each authentication character into-said section of a text message.

Preferably, each message contains an identification portion identifying

the sender-of the message, said authenticate character being contained within said identification portion.

In yet another aspect, the present invention consists in a method of authenticating transmission of a textbased message, comprising composing a message--at a higher ievei access centre, entering into a part of the message non-editable at a common level-of access an authentication character not enterable at the common level of access, and transmitting the message to a common level platform, where the message is received, the authentication character in the non-editable part being displayed.

In still another aspect, the present invention consists in a messaging system in-which text messages are transmitted wifeessly between mobile handsets and from at least one authenticated station to multiple handsets, each textmessage generated by a handset comprising first and second automatically generated sections, the content of the first section being under the controt-of the handset user and the content of the second section being under the : controt of the message system, the authenticated station being

adapted oeferate authenticated iessages irhwhich content ofhe first section is-arranged to match the content of the second section.

Advantageously, the content of said second section comprises a time of transmission.

The invention will now be described by way of example with reference to the accompanying drawings, in which : Figure 1 is a diagram illustrating a method of message authentication accordingtoanembodimentoftheinvention; Figure 2 is a diagram illustrating a known-method of message authentication ; and Figure-3 is a diagram iJJustrating a method of message authentication according-to another embodiment of the invention.

Most devices employing-simple messaging systems also employ fairly basic text-entry methods. These will typically involve simple typing of characters, with little or no provision for formatting of the text. The message

eventual) ydisplayed will typically reproduce only the characters entered. However, stiast tavo of the characters which may be entered in composing such messages are characters which are not displayed in the message. The most obvious examples are "SPACE", which inserts a blank space of character size, and "RETURN" which sends the editing cursor to the next line of text Given two such non-displayed characters, it is hence possible to construct a binary code which may not be read by a typical recipient-of the message,-and may only be read by a decoding device, albeit a very simple one. The presence of such a binary code can be'hidden'from a typical recipient of lhe text message if this binary code is positioned at the end of a visible, alpha-numerical text message. In this way, a "watermark" can be added to simple text messages, for purposes of verification.

Figure 1 frustrates an implementation of such non-displayed code in an embodiment of the invention. A message is composed at a message centre (100), which has a higher level of access into the messaging network.

For example, the message maybe able to be edited in different ways from those composed on the recipient devices. A watermark type code is then Inserted into the message, containing details wrnch wit) allow the recipient to be verified as the intended one. This is composed by entenng a sequence of non-pnntll19 characters, such as RETURN and SPACE, to form binary code which translates, for example, to password, a particular date, an intended recipient's identification details, or even a company logo. In the editing application employed to compose the message, the non-printing characters may be denoted by other characters, as is common in word processing applications, in order to verify that the correct code hasten entered.

The message is transmitted {1-02) to a recipient (1D4). In this embodiment, the common part of the message will be viewable by the user, but the code will not. The mark--up characters employed in the editing are not

displayed, merely the RETURN's and SPACE's entered, which, of course, are non-printing characters.

In order for the recipient to demonstrate that they are an intended or genuine recipient, the message is transmitted (1-06) to a decoding platform (108). This-Wil have some means for reading the sequence of non-printing characters, which might be to use a similar system of mark-up characters m employed-in the initial editing stage. The code may then be read, and the recipient verified.

It will be recognized that there are myriad ways in which this and similar techniques of steganographywill beof use in commercial applications of text messaging.

In an alternative embodiment, the watermark may be added automatically to a message. Many text based messaging systems employ a signature-adding function, whereby a short section of text is added to the end of every message sent from a particular user or platform. This could contain the non-printing binary sequence as a type of seal. For example, the

signature-could be programmed mto a particuiarjuser's jnessagB-compiler without their-knowing, as the-signature would not be dspayed. A r-ectpient with theapabUity todecodehegnaturewouMhen ab ! e to distinguish a message from-the parttcuiarsenderfro those-rrom others (assuming no other distinction were available).

On certain platforms, such systems might be circumvented. For example, if a text message is sent via the SMS system from one mobile telephone-to another, it is a simple matter to forward the message ) n to another telephone, thereby forwarding any necessary watermark information, and potentially giving for intended more than one recipient access to the information one recipient only.

The Short Message System- (SMS) ofext jnessaging '"iexting" allows a user of a moere telephone to enter a number of characters into a message via the keypad, and send 4t -to another user with a mobile phone employing-the-same system-When the message is sent, a header and footer are automatical generated to accompany it The header and footer typically

include the telephone number of the sender, and the footer may also include a time and date stamp. When a message is received, the header of the message is typically viewed initially, or alongside the message, in-order to indicate the render, and the footer may also be displayed, or accessed by some means.

One simple commercial application of SMSis for transmitting detail of an event, and SMS may employed in particular to transmit a voucher or permit for entry to or attendance at an event. it would be simple to duplicate such vouchers by sending the message on to any number of other mobile phone users. Rudimentary protection is provided by the fact that a voucher message which was naively forwarded by the intended recipient to on or more unauthorized recipients, would contain in the header, the name or number not of the company distributing the voucher but of the recipient forwarding the message. This rudimentary protection can, however, be overcome rather easily.

This will be+1OW explained in more detail. Referring to Figure 2, in an

attemptrvenfyhata recipient ofhe message js an miendsdme, an initial sender with higher level access to the message system couid replace the number in the header portion with the narne of a company The message would thus be transmitted (102) from the message centre (100) to a recipient (104). If tAts message were then forwarded (100) to other telephones, the header would-simply display the telephone number of the forwarder" (1D4).

Thus, only recipients able to display on their telephone the company name on the message header would be permitted entry.

This simple system may, however, be circumvented. Mobile telephones typically employ an address book system, whereby a particular number may be associated with a particular name, and that name displayed as the message header when a message from that number is received. If a second recipient (108) were to be informed of the company name, they could enter the forwarder's (104) number and associate this with the known company name in the address system. Thus, when the message header is displayed, the company name will be displayed as if the recipient (here

a genuine-one.

This is solved in-a further-embodiment of the invention. Typically, the higher levei access required to atter the header of a message also permits the typing of certain characters into the-header which are notavaiiabie to be entered by user on a typical handset. For example, a triangle or square may be added to the header, which would then be viewed upon receipt, but cotdd

not then be entered into-the addfess bookin order tG-dreumvent the-system.

Referring-te Figure the message (300) would e compoBBd- (100), including the header-or footer conwnftlhe nort-reproducable--characterThis would--then be sent to a recipient (204). If the recipient then forwards the message 206),-the header shown on-a miner iecipjBufs tt3ndsBt- (208) wi ! t be incorrect ; ttwin either the be number of the sender, or some text typed into the address book, but neither will have any of the non-reproduise

characters. The further Tecipjenfs message iMii therBibre tB Tviousiy Tnxaiid when cheeked for authenticity.

In an alternative-embodiment, the time stamp which is typically added to the footer of messages may also be added to the header at the initial composing-stage. In an authenticated message generating station, it will be rdativeJy simple to provide be of the form which entered for the same time value which is costomarily be also enteredasatime stamp Tn the message header. The time-stand in the message footer, to is not-enterable

by a user,-but this is not essential. n thisase, Dniy the first recipient wH < have the cdffecttm staTM, that is to : say a Aftm stwm in-the beader matching a time stamp-m the footer. A forwarded =essageoud of necessity Tiave new time stamp in Iheooler and it-wUi be very-difficult for a user of a mobile handsetio program a time value as a fake time stamp in the message header and then procure that the time stamp entered by the network on transmission of the message exactly matches ! hat fake. time. stamp.

In a further alternative, the construction of a non-viewable simple binary code Watermark', as described in the initial embodiment herein, may be used in the message body, In this case, the sequence may be reproducable by a non-intended recipient, in that the characters RETURN

and SPACE are available to them, but as the sequence is not seen in the message body-by therst recipient it will not be obvious to the bogus recipient to alter the binary code watermark as might be required to authenticate the bogus recipient.

For exampiRaTDBSsage mighib cornposedennitting entry toman event at a highefevei access centfe 00). The message header is given the name of the company, and a binary sequence of non-printing characters is transmitted -Within the message body. This binary sequence is a watermark whose code-reflects some identifiable aspect of the first recipient (204). The

first recipient (2M) might then inform a second recipient (208) of the company O'that'theymigh enr'thatname ilheiraddress hnok system so-as to correspond with the first recipient's number. On feceivina the message, the second recipient wi then display the company name in the header, but will not have the correct watermark in the message body Thus when the message is verified, perhaps by a system in which the message must be forwarded to a decoder upon entry to the event, it will be invalid, and the second recipient could be barred.

When a bogus recipient is discovered, it would then be possible to determine which first recipient sent them the message, and hence this first recipient could also be barred It will be appreciated by those skilled in the art that the invention has been described by way of example only, and a wide variety of alternative approaches may be adopted.

Claims

1. A messaging system in which text messages are transmitted wirelessly to mobile handsets each having a display, there being a protocol for the transmission. of a defined set of characters with the display of each handset being : adapted to dispiay alpha-numeric characters from said set, wherein selected text messages are coded by the introduction into the text message of a code sequence of characters from the defined set, which characters are not displayed on the handset displays.

?. A messaging-system according to Claim 1, comprising an authentication station adapted to read said code sequence.

3. A messaging system according to Claim 1 in which at least some of the mobile handsets have a-keypad enaMngentry of certain characters from the defined character set, thecode-sequence compfising

characteTsected from said certain characters.

/-. A messaging system according to any one of bairns 1 to 3, in which code sequenceindi-the dianacter D--p itbujaspace orthe tharacter representingareturn.

5. A messaging system according to Claim 1, in which-at least some of the mobile handsets have a key pad enabling entry of certain characters from the defined character set, the code sequence comprising

characters sntry TrdchTs not enabled i) y-said key paft,-the system comprising a separate code generating station.

6. A messaging system in which text messages-are transmitted wirelessly to mobile handsets each having a display and a key pad for the entry of characters, there being a protect for the transmission of-aefmed transmissmset-Df zharacters-with Ihe-displaynf Each fumubet being adapted to dtspiay-each-character if) iepiay-sub-eetf the transmission-c, et of charactei : s and with the key pad of each JuiMset being d < AptedoBntertmlycharacters from : a-keypad'snb-=SBt-Df the transmissieset of characters, whefem selected ext meseages ate authenticated. at. an authenticated message generation statlon-by the introduction dniotheext message message of one or more authentication characters wrHC form part of-the display u-set but which do not form part of Ihe key pad sub-set.

A messagmg system accordk to Caim 6, wrMch each-text message contains asectonMdiich is aulomattcatty generated on transmission of the message by attandset. the message-generation statcon being adapted to introduce the or-each atjthenticatton character into said section of-a-text message.

A messaging system according to Claim 6 or Claim 7, in which-each message contains an identification portion identifying the render of the messageaid authentttcation character being contained wtihm-said 4dentificatton portion.

A method of authenticating transmission of a texttased message, comprising composing < )-message at higher 4evei access centre, entering ic p rtnflhBTnessagBitim-BdiiatB tHammDnJeMeiof access an authentication chafacterot-enterabie at the conwnon evei of access, and transmitting the message a common leveiplatform, where the message is received, the authentication character in the non-editabie part being displayed.

) 0. A messaging system in which text messages are transmitted wirelessly between mobile handsets and from at least one authenticated station to multiple-handsets, each text message generated by a handset comprising first and second automatically generated sections, the- content of the first section being under the control of the handset user and the content of the second section being under the control of the message system, the authenticated station being adapted to generate authenticatedmsssages in which content of the first section is arranged to match the content of the second section.

A messaging system according to Claim 10, in which the content of said second section comprises time of transmission.