Patent Publication Number: US-2007123217-A1

Title: Display of secure messages on a mobile communication device

Description:
This invention relates generally to the display of messages on mobile communication devices, and particularly to the display of secure messages on such devices.  
      Mobile communication devices with display screens are used to receive and display electronic messages in text or graphical format. It is desirable for such devices to display received messages, such as e-mail messages, to users without excessive delay in new information being displayed on the screens of the devices.  
      However, it is common for electronic messages to include more information than that which will typically be displayed by a mobile communication device. For example, an e-mail message as sent may repeat the body of the message several times in different formats. It is common for the same content to be included in plaintext format, in rich text format and in HTML (hypertext markup language) format. At the mobile communication device, it is typically only appropriate to display the message body in one of the possible formats. Often, for reasons of efficiency, only the plaintext version of the message body will be displayed.  
      Where a user employs a mobile communications environment in which messages are forwarded to the device from a message server, the server may be configured to send only a single version of the message body to the mobile communications device. This provides efficiencies in the communication to the mobile communication device. From the perspective of the user of the device, such an approach will reduce the time that would otherwise have been taken for the mobile communications device to receive, process and redraw the screen as required by the device operation when in receipt of the differently formatted information.  
      However, this approach may not be available when mobile communication devices are configured to receive messages that are sent in accordance with a secure message format such as the Secure Multipurpose Internet Mail Extension (S/MIME) format. For such messages to be verified by a mobile communication device, it is often required that the entire message (or a significant portion of the message) be received by the device. However, where differently formatted message body information is repeated in the message, the secure message will include more data than will be displayed by the mobile communication device. As a result, the user of the device may experience undesirably slow performance while the device carries out processing steps relating to the data that is not displayed to the user but which steps are carried out as the device receives the information necessary to enable the message to be verified by the device.  
      Accordingly, it is desirable to provide a system and method for the display of secure messages on a mobile communications device in which a secure message may be received and displayed by the device without causing undue delays in message display. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an overview of an example communication system in which a wireless communication device may be used.  
       FIG. 2  is a block diagram of a further example communication system including multiple networks and multiple mobile communication devices.  
       FIG. 3  is a block diagram of a wireless mobile device usable in the example communication system.  
       FIG. 4  is a flowchart showing the steps taken by a wireless mobile device to communicate with a message server to manage the forwarding of information to the device.  
       FIG. 5  is a flowchart showing the steps taken by a message server to manage the forwarding of information that may be encrypted to a wireless mobile device. 
    
    
     DETAILED DESCRIPTION  
      Accordingly, a system on a mobile communications device is provided for the display of an incrementally received secure message. The system includes a message viewer application for scanning the received portions of the message. On determination that the received portion of the message includes a first displayable portion of the message content, the system signals to a message server to halt the message server from forwarding further portions of the message content. The system further provides a mechanism for the user of the mobile communications device to cause the mobile communications device to further signal the message server to recommence the forwarding of further portions of the secure message content to permit the verification of the e-mail based on the further portions of the secure message content.  
      Advantages include improved display performance for the user of a mobile communications device due to the halt in information being received from the message server where the mobile device will process, but not display, the information that would otherwise be initially received by the mobile communications device. However, the user remains able to carry out a security verification of the received message at the mobile communications device.  
      The invention in one aspect comprises a method for receiving a message on a mobile communications device, the message comprising a displayable message content portion capable of being viewed on the mobile communications device, the end of the displayable message content portion being identified by a predefined indicator, the method comprising the steps of: receiving a first segment of the message; scanning the first segment for the predefined indicator; if the predefined indicator is not found within the first segment, automatically receiving a further segment of the message; and scanning the further segment of the message for the predefined indicator.  
      In another aspect, the invention comprises a method for receiving a message on a mobile communications device, the message comprising a displayable message content portion capable of being viewed on the mobile communications device, the end of the displayable message content portion being identified by a predefined indicator, the method comprising the steps of: receiving a first segment of the message; scanning the first segment for the predefined indicator; if the predefined indicator is not found within the first segment, automatically receiving a further segment of the message; and scanning the further segment of the message for the predefined indicator, wherein the first and any further segment is transmitted to the mobile communications device by a server, the method further comprising the step of automatically transmitting a command to the server to transmit a further segment of the message, said step of transmitting a command being executable at any time during the method.  
      In a further aspect, the invention comprises a computer program product comprising code operative to carry out the steps of any of the aforesaid methods.  
      In a further aspect, the invention comprises a system for the display of a message receivable on a mobile communications device to a user, the message being automatically incrementally forwarded in segments to the mobile communications device by a message server, the message comprising a message content portion displayable on the mobile communications device, the system comprising: means adapted to scan received segments of the message to determine if the entirety of a first displayable portion of the message has been received by the mobile communications device; and means adapted to signal the message server to prevent the automatic incremental forwarding of segments of the message on the determination that the entirety of a first displayable portion has been received.  
       FIG. 1  is an overview of an example communication system in which a wireless communication device may be used. One skilled in the art will appreciate that there may be other different topologies, but the system shown in  FIG. 1  helps demonstrate the operation of the secure message processing systems and methods described in the present application. There may also be many message senders and recipients. The simple system shown in  FIG. 1  is for illustrative purposes only.  
       FIG. 1  shows an e-mail sender  10 , the Internet  20 , a message server system  40 , a wireless gateway  85 , wireless infrastructure  90 , a wireless network  105  and a mobile communication device  100 .  
      An e-mail sender system  10  may, for example, be connected to an ISP (Internet Service Provider) on which a user of the system  10  has an account, located within a company, possibly connected to a local area network (LAN), and connected to the Internet  20 , or connected to the Internet  20  through a large ASP (application service provider) such as America Online (AOL). Those skilled in the art will appreciate that the systems shown in  FIG. 1  may instead be connected to a wide area network (WAN) other than the Internet, although e-mail transfers are commonly accomplished through Internet-connected arrangements as shown in  FIG. 1 .  
      The message server  40  may be implemented, for example, on a network computer within the firewall of a corporation, a computer within an ISP or ASP system or the like, and acts as the main interface for e-mail exchange over the Internet  20 . Although other messaging systems might not require a message server system  40 , a mobile device  100  configured for receiving and possibly sending e-mail will normally be associated with an account on a message server. Perhaps the two most common message servers are Microsoft Exchange™ and Lotus Domino™. These products are often used in conjunction with Internet mail routers that route and deliver mail. These intermediate components are not shown in  FIG. 1 , as they do not directly play a role in the secure message processing described below. Message servers such as server  40  typically extend beyond just e-mail sending and receiving; they also include dynamic database storage engines that have predefined database formats for data like calendars, to-do lists, task lists, e-mail and documentation.  
      The wireless gateway  85  and infrastructure  90  provide a link between the Internet  20  and wireless network  105 . The wireless infrastructure  90  determines the most likely network for locating a given user and tracks the user as they roam between countries or networks. A message is then delivered to the mobile device  100  via wireless transmission, typically at a radio frequency (RF), from a base station in the wireless network  105  to the mobile device  100 . The particular network  105  may be virtually any wireless network over which messages may be exchanged with a mobile communication device.  
      As shown in  FIG. 1 , a composed e-mail message  15  is sent by the e-mail sender  10 , located somewhere on the Internet  20 . This message  15  is normally fully in the clear and uses traditional Simple Mail Transfer Protocol (SMTP), RFC822 headers and Multipurpose Internet Mail Extension (MIME) body parts to define the format of the mail message. These techniques are known to those skilled in the art. The message  15  arrives at the message server  40  and is normally stored in a message store. In a preferred embodiment described in further detail below, messages addressed to a message server account associated with a host system such as a home computer or office computer which belongs to the user of a mobile device  100  are redirected from the message server  40  to the mobile device  100  as they are received.  
      Regardless of the specific mechanism controlling the forwarding of messages to the mobile device  100 , the message  15 , or possibly a translated or reformatted version thereof, is sent to the wireless gateway  85 . The wireless infrastructure  90  includes a series of connections to wireless network  105 . These connections could be Integrated Services Digital Network (ISDN), Frame Relay or T1 connections using the TCP/IP protocol used throughout the Internet. As used herein, the term “wireless network” is intended to include three different types of networks, those being (1) data-centric wireless networks, (2) voice-centric wireless networks and (3) dual-mode networks that can support both voice and data communications over the same physical base stations. Combined dual-mode networks include, but are not limited to, (1) Code Division Multiple Access (CDMA) networks, (2) the Groupe Special Mobile or the Global System for Mobile Communications (GSM) and the General Packet Radio Service (GPRS) networks, and (3) future third-generation (3G) networks like Enhanced Data-rates for Global Evolution (EDGE) and Universal Mobile Telecommunications Systems (UMTS). Some older examples of data-centric network include the Mobitex™ Radio Network and the DataTACTM Radio Network. Examples of older voice-centric data networks include Personal Communication Systems (PCS) networks like GSM, and TDMA systems.  
       FIG. 2  is a block diagram of a further example communication system including multiple networks and multiple mobile communication devices. The system of  FIG. 2  is substantially similar to the  FIG. 1  system, but includes a host system  30 , a redirection program  45 , a mobile device cradle  65 , a wireless virtual private network (VPN) router  75 , an additional wireless network  110  and multiple mobile communication devices  100 . As described above in conjunction with  FIG. 1 , FIG.  2  represents an overview of a sample network topology. Although the message processing systems and methods described herein may be applied to networks having many different topologies, the network of  FIG. 2  is useful in understanding an automatic e-mail redirection system mentioned briefly above.  
      The central host system  30  will typically be a corporate office or other LAN, but may instead be a home office computer or some other private system where mail messages are being exchanged. Within the host system  30  is the message server  40 , running on a computer within the firewall of the host system that acts as the main interface for the host system to exchange e-mail with the Internet  20 . In the system of  FIG. 2 , the redirection program  45  enables redirection of data items from the server  40  to a mobile communication device  100 . Although the redirection program  45  is shown to reside on the same machine as the message server  40  for ease of presentation, there is no requirement that it must reside on the message server. The redirection program  45  and the message server  40  are designed to co-operate and interact to allow the pushing of information to mobile devices  100 . In this installation, the redirection program  45  takes confidential and non-confidential corporate information for a specific user and redirects it out through the corporate firewall to mobile devices  100 . A more detailed description of the redirection software  45  may be found in the commonly assigned U.S. Pat. No. 6,219,694 (“the &#39;694 Patent”), entitled “System and Method for Pushing Information From A Host System To A Mobile Data Communication Device Having A Shared Electronic Address”, and issued to the assignee of the instant application on Apr. 17, 2001, which is hereby incorporated into the present application by reference. This push technique may use a wireless friendly encoding, compression and encryption technique to deliver all information to a mobile device, thus effectively extending the security firewall to include each mobile device  100  associated with the host system  30 .  
      As shown in  FIG. 2 , there may be many alternative paths for getting information to the mobile device  100 . One method for loading information onto the mobile device  100  is through a port designated  50 , using a device cradle  65 . This method tends to be useful for bulk information updates often performed at initialization of a mobile device  100  with the host system  30  or a computer  35  within the system  30 . The other main method for data exchange is over-the-air using wireless networks to deliver the information. As shown in  FIG. 2 , this may be accomplished through a wireless VPN router  75  or through a traditional Internet connection  95  to a wireless gateway  85  and a wireless infrastructure  90 , as described above. A VPN connection could be established directly through a specific wireless network  110  to a mobile device  100 . The possibility of using a wireless VPN router  75  is contemplated to be used with Internet Protocol (IP) Version 6 (IPV6) on IP-based wireless networks. This protocol will provide enough IP addresses to dedicate an IP address to every mobile device  100  and thus make it possible to push information to a mobile device  100  at any time. A principal advantage of using this wireless VPN router  75  is that it could be an off-the-shelf VPN component, thus it would not require a separate wireless gateway  85  and wireless infrastructure  90  to be used. A VPN connection would preferably be a Transmission Control Protocol (TCP)/IP or User Datagram Protocol (UDP)/IP connection to deliver the messages directly to the mobile device  100 . If a wireless VPN  75  is not available then a link  95  to the Internet  20  is the most common connection mechanism available and has been described above.  
      In the automatic redirection system of  FIG. 2 , a composed e-mail message  15  leaving the e-mail sender  10  arrives at the message server  40  and is redirected by the redirection program  45  to the mobile device  100 . As this redirection takes place the message  15  is re-enveloped, as indicated at  80 , and a possibly proprietary compression and encryption algorithm can then be applied to the original message  15 . In this way, messages being read on the mobile device  100  are no less secure than if they were read on a desktop workstation such as  35  within the firewall. All messages exchanged between the redirection program  45  and the mobile device  100  preferably use this message repackaging technique. Another goal of this outer envelope is to maintain the addressing information of the original message except the sender&#39;s and the receiver&#39;s address. This allows reply messages to reach the appropriate destination, and also allows the “from” field to reflect the mobile user&#39;s desktop address. Using the user&#39;s e-mail address from the mobile device  100  allows the received message to appear as though the message originated from the user&#39;s desktop system  35  rather than the mobile device  100 .  
      With reference back to the port  50  and cradle  65  connectivity to the mobile device  100 , this connection path offers many advantages for enabling one-time data exchange of large items. For those skilled in the art of personal digital assistants (PDAs) and synchronization, the most common data exchanged over this link is Personal Information Management (PIM) data  55 . When exchanged for the first time this data tends to be large in quantity, bulky in nature and requires a large bandwidth to get loaded onto the mobile device  100  where it can be used on the road. This serial link may also be used for other purposes, including setting up a private security key  111  such as an S/MIME or PGP (Pretty Good Privacy data encryption) specific private key, the Certificate (Cert) of the user and their Certificate Revocation Lists (CRLs)  60 . The private key is preferably exchanged so that the desktop  35  and mobile device  100  share one personality and one method for accessing all mail. The Cert and CRLs are normally exchanged over such a link because they represent a large amount of the data that is required by the device for S/MIME, PGP and other public key security methods.  
      S/MIME is a message security protocol that enables end-to-end authorization and protection of data integrity and privacy from the time that the originator sends the message until the message recipient decodes and reads the message. S/MIME allows message senders to digitally sign messages using their digital signature, encrypt messages with the recipient&#39;s public key, or both digitally sign and encrypt the message.  
      In the preferred embodiment an S/MIME message may be verified both at message server  40  and at mobile device  100 , both shown in  FIG. 2 . For a user of the mobile communications device, verification at mobile device  100  provides a higher level of security than relying on the verification at message server  40 . In some cases, however, the verification at message server  40  may be sufficient for the user. In mobile device  100 , a verification application is executable to determine if some or all of a received message meets message security protocol requirements. The verification application executed on the mobile device  100  may decrypt the message received at the mobile device  100 , or it may verify a digital signature appended to the message, or it may both decrypt and verify a digital signature, depending on whether the message received was encrypted, signed, or both signed and encrypted, respectively. If the verification application is executed at the message server  40 , the verification application may still decrypt, verify the digital signature of, or both decrypt and verify the digital signature of a message received at the server  40 , but the resultant decrypted message then delivered to the mobile device  100  could thus be subject to tampering undetected by the user of the mobile device  100  upon receipt of the resultant message.  
      In some cases, the verification application executable by mobile device  100  will be unable to complete the verification process without receipt of the entire message or a significant portion of the message. For example, where a portion of a message is digitally signed it is typical for the verification of the signature to rely on the content of that portion of the message. Thus where a portion of the message, perhaps as much as the entire message body itself, is encoded or signed in this way, this portion of the message subject to verification, as well as any digital certificate attached to the message, must be received by mobile device  100  before verification at mobile device  100  is able to be carried out. If the message to be verified comprises other file attachments, then typically all of the attachments must be received by the mobile device  100  before the verification application can verify the message.  
      The above operational characteristic may adversely affect the speed at which information is displayed to a user of mobile device  100 . This is particularly the case where the message being received by mobile device  100  has either repeated message body contents (as where plaintext, rich text and/or HTML formatted message body versions are included) or attachments. In either case, information may be received which information is not displayable to the user or is not intended to be displayed to the user of the mobile device  100 .  
      An approach to solving this potential adverse impact on perceived device responsiveness is for the message server  40  to edit messages being forwarded to the mobile communication device  100 . Such an editing step can remove certain repeated portions of the message body. For example, if the message received at the message server  40  contains the content of the message in plaintext and in HTML, then the server  40  could strip out the HTML portion of the message before forwarding it to the mobile device  100 . However, where the mobile communication device  100  executes a verification application, it will not be possible for the message server  40  itself to automatically edit messages to remove such repeated portions, since this would cause the verification step to fail.  
      Accordingly, the execution of a verification application by the mobile device  100  may require the device  100  to receive non-displayable or repetitive portions before verification can be accomplished, and consequently the mobile device  100  may exhibit slower than optimal display characteristics as the non-displayable or repetitive information is received and processed by mobile device  100 .  
      According to the preferred embodiment, however, a message viewer application for displaying messages to a user executable on the mobile communication device  100  also operates to potentially reduce the number of portions of the message that will be forwarded by the message server  40 . In the preferred embodiment, mobile communication device  100  is able to communicate with the message server  40  to manage the forwarding of information to the device. As shown in  FIG. 4 , the message data for a first message received by the message server  40  is forwarded to the mobile communication device  100  in segments or chunks of predetermined size (for example, in segments of up to 1 kilobyte), initially with a first segment being forwarded at step  405 . This first segment comprises only content that can be displayed to the user on the mobile device  100 ; so, for example, if the message is encrypted, the segment may be empty if the message was not previously decrypted by the message server  40 . In that case, the user would see only header information for the message (e.g., the sender information, the timestamp, or the subject line) and would be advised by the message viewer application that additional content is available for downloading and verification by the verification application. Otherwise, if the message is not encrypted, the first segment sent at step  405  comprises message content.  
      After receipt of each segment at the mobile communication device  100 , the message viewer application scans the message data received in that segment at step  410 . There are two results of the segment scan at step  410  that are shown in  FIG. 4 . At decision step  430  (described below), the renderable nature of the segment determines future steps. At decision step  431 , the presence of a delimiter determines whether a complete renderable portion of the message has been received at the mobile device  100 . For example, if the message viewer application on the mobile device  100  is capable of displaying plaintext content to the user, as opposed to other formats such as Rich Text Format (RTF) or HTML, the message viewer application scans for a predetermined indicator, such as a defined boundary delimiter, that is known to define the end of plaintext content. In the preferred embodiment, the message is defined using the S/MIME protocol and therefore different parts of the message body are delimited in defined ways. For example, a plaintext portion of the message body is preceded by a defined boundary delimiter such as “--Part_Boundary_Alternative” with a content format specifier, for example, “Content-Type: text/plain”. Similar content format specifiers (“Content-Type: text/html” and “Content-Type: text/RTF” for HTML and RTF format, respectively) may be found in message content portions of messages received by the mobile communication device  100 . Thus, the message view application at step  410  may scan or search the received message segment for the presence of “--Part_Boundary_Alternative Content-Type: text/plain”. If such a delimiter, or other predefined indicator, is found in the message segment, then the message view application may determine that it has received a complete portion of plaintext content and instructs the server  40  to cease sending further segments at step  415 . If such a delimiter is not found in the message segment by the scan, then a further message segment is automatically delivered to the mobile communication device  100  by the message server  40  at step  405 . The further message segment is similarly scanned or searched at step  410 , and yet a further message segment is automatically delivered at step  405  from the message server  40  if the delimiter is not found. At any time during this process, the user of the mobile communication device  100  may view the segments of the message that have already been downloaded to the mobile device  100 .  
      Thus, in the preferred embodiment, the scan carried out by the message viewer application parses the incoming message segments to determine whether a first set of plaintext information has been received. In preferred embodiment given above, the delimiters are defined in accordance with Request for Comment 2046 (RFC 2046), which describes MIME alternate encodings of message text. In particular, section 5.1.4 of RFC 2046 describes the inclusion of alternative parts in “order of increasing faithfulness to the original content”. In practice in accordance with this order of increasing faithfulness, the most simple encoding (typically plaintext) is included in the message prior to other encodings (HTML and Rich Text, for example). Thus, by following the method outlined above, a complete portion of plaintext content may be downloaded without user intervention, and without downloading message segments comprising exclusively non-displayable or repetitive information to the mobile device  100 .  
      In the preferred embodiment, the automatic delivery of the further segments with each repeated execution of step  405  is controlled by a command referred to here as the AUTO MORE command. Preferably, the AUTO MORE command is specified by the mobile communication device  100  by default, although it may be manually specified by the user. When the default, or user-specified, AUTO MORE command is invoked, a predefined indicator, which may be a flag set in a communication from the device to the server, is sent by the mobile communication device  100  to the message server  40  at step  395 . On receipt of the predefined indicator, the message server  40  will carry out steps to send the further message segments to the mobile communication device  100 , without further requests being required from the user of the mobile device  100 .  
      Although in  FIG. 4  step  395  is shown as being executed prior to step  405 , persons skilled in the art will appreciate that the step may be executed at other points in the process; for example, the predefined indicator may have already been received by the message server  40  prior to receipt of the message at the server  40  (this may be the case if the AUTO MORE command is invoked by default). Alternatively, step  395  may be executed by the mobile communication device  100  after receipt of a message segment at step  405 ; for example, the indicator may be sent to the message server  40  together with other data acknowledging receipt of the message segment. Preferably, the predefined indicator is communicated to the message server  40  at intervals, or during any other status communication between the mobile communication device  100  and the message server  40 . In the preferred embodiment, the message viewer application communicates the predefined indicator to the message server  40 . In alternate embodiments, a software module on the mobile communication device  100  may instead be configured to communicate the predefined indicator to the message server  40  based on commands sent between the message viewer application and the software module.  
      If the message viewer application on the mobile device  100  detects the predetermined delimiter in a received message segment, the AUTO MORE command for that particular message is disabled, and this is communicated to the server  40  at step  415 . The message server  40  is thus instructed to cease sending segments of that message to the mobile device  100 .  
      This heuristic is adopted in the preferred embodiment based on the assumption that the viewable content to be received by mobile communications device  100  is contained in the first plaintext portion of the message content. In fact, other portions of the message may contain plaintext portions, or the mobile device may include functionality to permit display of the message content having other encodings. In the preferred embodiment efficiencies are obtained by using the heuristic described. Preferably, the downloading of further message segments is executed by the mobile communication device  100  only when the user is viewing the content downloaded so far of that particular message, in order to reduce memory usage on the mobile device  100 . However, in an alternate embodiment, the message viewer application may scan the initial message segments of other messages not currently being viewed by the user and download the remaining displayable portions of those other messages according to the method described above. This embodiment may be less desirable, as it increases the volume of data transmission between the mobile device  100  and the message server  40 .  
      In the preferred embodiment, the potential for perceived delays in the operation of the mobile device is reduced due to the message server  40  halting the automatic forwarding of content to the mobile communication device  100 , as described above. Content that is not viewable in the preferred embodiment by the mobile communication device  100  is not automatically forwarded to the device by the message server  40 . In the situation where the message comprises signed, encrypted, or signed and encrypted content which is not readily viewable by the message viewer application, some efficiencies may still be realized. The message viewer application, upon recognition of the message as an encrypted message at step  430 , may disable the AUTO MORE command at step  415 . The user may then optionally manually invoke the AUTO MORE mode in order to download and verify the content of the entire message. Preferably, if the message viewer application recognizes the application as being digitally signed but not encrypted, the message viewer application still receives a further segment  405  if the delimiter or other predefined indicator is not found in the first segment, since the message still contains displayable content besides the digital certificate attached to the message.  
      Thus, the ability to verify a signed and/or encrypted S/MIME message remains available to the user of the device  100 . In this scenario, the message viewer application may alternatively provide a VERIFY command to be manually invoked by the user, which both invokes the AUTO MORE command, and then invokes the verification application after all segments of the signed and/or encrypted message have been downloaded.  
      It will be appreciated that this approach to the display of secure e-mails will require the user to be familiar with the potential for the received message to have a tentative security status. A received S/MIME message may be accompanied by an indication that the message server  40  has verified the message, but the message may also be indicated to the user to have an indeterminate status as to verification at the mobile device. The user&#39;s command to receive further portions of the message (by use of AUTO MORE, for example), if selected, will result in other parts of the message being forwarded to allow the verification process at the mobile device to be carried out. In the meantime, the user experience is enhanced as there is a reduction in response time at the mobile device  100  due to the reduction in non-viewable information being forwarded to the device  100 .  
      In a further preferred embodiment, further efficiencies are provided for viewing the displayable portions of a message. Referring to  FIG. 5 , after the server  40  receives a message for forwarding at step  440 , server  40  sends a first segment at step  445 . As referred to above, preferably this first segment comprises message content, but in the circumstance where the message is encrypted, the first segment may not comprise any message content unless it is decrypted at the server  40 .  
      If the user of mobile communications device  100  wishes to view the remainder of the displayable portion of the message, the user may send a MORE ALL command to the message server  40 . This MORE ALL command may be invoked manually, or it may be set as a default on the mobile communication device  100 . If the MORE ALL command is not sent to the message server  40 , the steps referred to below will not be carried out by the server of the preferred embodiment. In either case, the mobile device  100  transmits a predetermined indicator to the message server  40  requesting the remainder of the displayable portion of the message. Once the server  40  receives this MORE ALL command (decision branch  450 ), the server  40  parses the remainder of the message at step  455  in order to identify the end of the portion of the message content comprising content that is displayable to the user on the mobile device  100 . This parsing step is generally similar to the step  410  described in the context of the mobile device  100  with respect to each individual segment received at the device  100 . However, in this particular embodiment, it is the message server  40  that scans the message for the delimiter or other predefined indicator identifying the end of the displayable (such as plaintext) portion of the message.  
      As is described in more detail below, once the complete displayable portion of the message is found by identifying the delimiter within the message, the message server  40  then transmits the displayable portion of the message to the mobile device  100 . The transmission of the remaining displayable portion of the message may be carried out in a plurality of segments, as described above, or the remainder of the displayable portion may be transmitted as a single, larger segment. However the remainder of the displayable portion of the message is received by the mobile communication device  100 , it is the message server  40  that scans the message for the appropriate delimiter, and not the mobile device  100 . The transmission of any further segments of the displayable portion of the message by the server  40  is carried out without any further MORE ALL or AUTO MORE commands from the mobile device  100 . The MORE ALL and AUTO MORE commands described above may be used concurrently with respect to the same message being viewed on the mobile device  100 . While the AUTO MORE command may be invoked by default, and the mobile device  100  may scan each received message segment for the predefined indicator or delimiter indicating the end of the displayable portion of the message, the user may manually intervene and hasten the downloading of the entire viewable content of the message to the mobile device by invoking the MORE ALL command. Preferably, the MORE ALL command is available to be invoked by the user via a menu option or other command keystroke or action in the message viewing application.  
      In the event that the message received by the message server  40  is digitally signed, encrypted, or both digitally signed and encrypted, some efficiencies may still be realized using the MORE ALL command. If the message is digitally signed (see decision branch  460 ), then upon receiving the MORE ALL command from the mobile communication device  100 , the message server  40  will have parsed the message to identify the displayable content of the message at step  455 , but also removes any digital certificates attached to the message (step  465 ) before transmitting the displayable message content to the mobile device  100  at step  470 . If the message is encrypted (or signed and encrypted)(see decision branch  475 ), then the displayable content within the message may be transmitted to the mobile device  100  pursuant to a MORE ALL command only if the message server  40  receives the session key applicable to the encrypted message from the mobile device  100  first.  
       FIG. 5  shows steps  480 ,  485  and  490  which carry out the decryption of the message, if the session key is available. As will be appreciated the server  40  will invoke a time out condition if the session key is not received.  
      As will be appreciated by those skilled in the art, this reduces the security of the message and is therefore less desirable. However, if the message server  40  is provided with the key and can decrypt the message, the message may then be parsed at step  455  and then the displayable portions transmitted to the mobile device  100  at step  470 .  
      As another example, the systems and methods disclosed herein may be used with many different computers and devices, such as a wireless mobile communications device shown in  FIG. 3 . With reference to  FIG. 3 , the mobile device  100  is a dual-mode mobile device and includes a transceiver  311 , a microprocessor  338 , a display  322 , non-volatile memory  324 , random access memory (RAM)  326 , one or more auxiliary input/output (I/O) devices  328 , a serial port  330 , an input device, such as a keyboard  332 , a speaker  334 , a microphone  336 , a short-range wireless communications sub-system  340 , and other device sub-systems  342 .  
      The transceiver  311  includes a receiver  312 , a transmitter  314 , antennas  316  and  318 , one or more local oscillators  313 , and a digital signal processor (DSP)  320 . The antennas  316  and  318  may be antenna elements of a multiple-element antenna, and are preferably embedded antennas. However, the systems and methods described herein are in no way restricted to a particular type of antenna, or even to wireless communication devices.  
      The mobile device  100  is preferably a two-way communication device having voice and data communication capabilities. Thus, for example, the mobile device  100  may communicate over a voice network, such as any of the analog or digital cellular networks, and may also communicate over a data network. The voice and data networks are depicted in  FIG. 3  by the communication tower  319 . These voice and data networks may be separate communication networks using separate infrastructure, such as base stations, network controllers, etc., or they may be integrated into a single wireless network.  
      The transceiver  311  is used to communicate with the network  319 , and includes the receiver  312 , the transmitter  314 , the one or more local oscillators  313  and the DSP  320 . The DSP  320  is used to send and receive signals to and from the transceivers  316  and  318 , and also provides control information to the receiver  312  and the transmitter  314 . If the voice and data communications occur at a single frequency, or closely-spaced sets of frequencies, then a single local oscillator  313  may be used in conjunction with the receiver  312  and the transmitter  314 . Alternatively, if different frequencies are utilized for voice communications versus data communications for example, then a plurality of local oscillators  313  can be used to generate a plurality of frequencies corresponding to the voice and data networks  319 . Information, which includes both voice and data information, is communicated to and from the transceiver  311  via a link between the DSP  320  and the microprocessor  338 .  
      The detailed design of the transceiver  311 , such as frequency band, component selection, power level, etc., will be dependent upon the communication network  319  in which the mobile device  100  is intended to operate. For example, a mobile device  100  intended to operate in a North American market may include a transceiver  311  designed to operate with any of a variety of voice communication networks, such as the Mobitex or DataTAC mobile data communication networks, AMPS, TDMA, CDMA, PCS, etc., whereas a mobile device  100  intended for use in Europe may be configured to operate with the GPRS data communication network and the GSM voice communication network. Other types of data and voice networks, both separate and integrated, may also be utilized with a mobile device  100 .  
      Depending upon the type of network or networks  319 , the access requirements for the mobile device  100  may also vary. For example, in the Mobitex and DataTAC data networks, mobile devices are registered on the network using a unique identification number associated with each mobile device. In GPRS data networks, however, network access is associated with a subscriber or user of a mobile device. A GPRS device typically requires a subscriber identity module (“SIM”), which is required in order to operate a mobile device on a GPRS network. Local or non-network communication functions (if any) may be operable, without the SIM device, but a mobile device will be unable to carry out any functions involving communications over the data network  319 , other than any legally required operations, such as ‘911’ emergency calling.  
      After any required network registration or activation procedures have been completed, the mobile device  100  may the send and receive communication signals, including both voice and data signals, over the networks  319 . Signals received by the antenna  316  from the communication network  319  are routed to the receiver  312 , which provides for signal amplification, frequency down conversion, filtering, channel selection, etc., and may also provide analog to digital conversion. Analog to digital conversion of the received signal allows more complex communication functions, such as digital demodulation and decoding to be performed using the DSP  320 . In a similar manner, signals to be transmitted to the network  319  are processed, including modulation and encoding, for example, by the DSP  320  and are then provided to the transmitter  314  for digital to analog conversion, frequency up conversion, filtering, amplification and transmission to the communication network  319  via the antenna  318 .  
      In addition to processing the communication signals, the DSP  320  also provides for transceiver control. For example, the gain levels applied to communication signals in the receiver  312  and the transmitter  314  may be adaptively controlled through automatic gain control algorithms implemented in the DSP  320 . Other transceiver control algorithms could also be implemented in the DSP  320  in order to provide more sophisticated control of the transceiver  311 .  
      The microprocessor  338  preferably manages and controls the overall operation of the mobile device  100 . Many types of microprocessors or microcontrollers could be used here, or, alternatively, a single DSP  320  could be used to carry out the functions of the microprocessor  338 . Low-level communication functions, including at least data and voice communications, are performed through the DSP  320  in the transceiver  311 . Other, high-level communication applications, such as a voice communication application  324 A, and a data communication application  324 B may be stored in the non-volatile memory  324  for execution by the microprocessor  338 . For example, the voice communication module  324 A may provide a high-level user interface operable to transmit and receive voice calls between the mobile device  100  and a plurality of other voice or dual-mode devices via the network  319 . Similarly, the data communication module  324 B may provide a high-level user interface operable for sending and receiving data, such as e-mail messages, files, organizer information, short text messages, etc., between the mobile device  100  and a plurality of other data devices via the networks  319 . The microprocessor  338  also interacts with other device subsystems, such as the display  322 , the RAM  326 , the auxiliary input/output (I/O) subsystems  328 , the serial port  330 , the keyboard  332 , the speaker  334 , the microphone  336 , the short-range communications subsystem  340  and any other device subsystems generally designated as  342 .  
      Some of the subsystems shown in  FIG. 3  perform communication-related functions, whereas other subsystems may provide “resident” or on-device functions. Notably, some subsystems, such as the keyboard  332  and the display  322  may be used for both communication-related functions, such as entering a text message for transmission over a data communication network, and device-resident functions such as a calculator or task list or other PDA type functions.  
      Operating system software used by the microprocessor  338  is preferably stored in a persistent store such as non-volatile memory  324 . The non-volatile memory  324  may be implemented, for example, as a Flash memory component, or as battery backed-up RAM. In addition to the operating system, which controls low-level functions of the mobile device  310 , the non-volatile memory  324  includes a plurality of software modules  324 A- 324 N that can be executed by the microprocessor  338  (and/or the DSP  320 ), including a voice communication module  324 A, a data communication module  324 B, and a plurality of other operational modules  324 N for carrying out a plurality of other functions. These modules are executed by the microprocessor  338  and provide a high-level interface between a user and the mobile device  100 . This interface typically includes a graphical component provided through the display  322 , and an input/output component provided through the auxiliary I/O  328 , keyboard  332 , speaker  334 , and microphone  336 . The operating system, specific device applications or modules, or parts thereof, may be temporarily loaded into a volatile store, such as RAM  326  for faster operation. Moreover, received communication signals may also be temporarily stored to RAM  326 , before permanently writing them to a file system located in a persistent store such as the Flash memory  324 .  
      An exemplary application module  324 N that may be loaded onto the mobile device  100  is a personal information manager (PIM) application providing PDA functionality, such as calendar events, appointments, and task items. This module  324 N may also interact with the voice communication module  324 A for managing phone calls, voice mails, etc., and may also interact with the data communication module for managing e-mail communications and other data transmissions. Alternatively, all of the functionality of the voice communication module  324 A and the data communication module  324 B may be integrated into the PIM module.  
      The non-volatile memory  324  preferably also provides a file system to facilitate storage of PIM data items on the device. The PIM application preferably includes the ability to send and receive data items, either by itself, or in conjunction with the voice and data communication modules  324 A,  324 B, via the wireless networks  319 . The PIM data items are preferably seamlessly integrated, synchronized and updated, via the wireless networks  319 , with a corresponding set of data items stored or associated with a host computer system, thereby creating a mirrored system for data items associated with a particular user.  
      Context objects representing at least partially decoded data items, as well as fully decoded data items, are preferably stored on the mobile device  100  in a volatile and non-persistent store such as the RAM  326 . Such information may instead be stored in the non-volatile memory  324 , for example, when storage intervals are relatively short, such that the information is removed from memory soon after it is stored. However, storage of this information in the RAM  326  or another volatile and non-persistent store is preferred, in order to ensure that the information is erased from memory when the mobile device  100  loses power. This prevents an unauthorized party from obtaining any stored decoded or partially decoded information by removing a memory chip from the mobile device  100 , for example.  
      The mobile device  100  may be manually synchronized with a host system by placing the device  100  in an interface cradle, which couples the serial port  330  of the mobile device  100  to the serial port of a computer system or device. The serial port  330  may also be used to enable a user to set preferences through an external device or software application, or to download other application modules  324 N for installation. This wired download path may be used to load an encryption key onto the device, which is a more secure method than exchanging encryption information via the wireless network  319 . Interfaces for other wired download paths may be provided in the mobile device  100 , in addition to or instead of the serial port  330 . For example, a USB port would provide an interface to a similarly equipped personal computer.  
      Additional application modules  324 N may be loaded onto the mobile device  100  through the networks  319 , through an auxiliary I/O subsystem  328 , through the serial port  330 , through the short-range communications subsystem  340 , or through any other suitable subsystem  342 , and installed by a user in the non-volatile memory  324  or RAM  326 . Such flexibility in application installation increases the functionality of the mobile device  100  and may provide enhanced on-device functions, communication-related functions, or both. For example, secure communication applications may enable electronic commerce functions and other such financial transactions to be performed using the mobile device  100 .  
      When the mobile device  100  is operating in a data communication mode, a received signal, such as a text message or a web page download, is processed by the transceiver module  311  and provided to the microprocessor  338 , which preferably further processes the received signal in multiple stages as described above, for eventual output to the display  322 , or, alternatively, to an auxiliary  1 / 0  device  328 . A user of mobile device  100  may also compose data items, such as e-mail messages, using the keyboard  332 , which is preferably a complete alphanumeric keyboard laid out in the QWERTY style, although other styles of complete alphanumeric keyboards such as the known DVORAK style may also be used. User input to the mobile device  100  is further enhanced with a plurality of auxiliary I/O devices  328 , which may include a thumbwheel input device, a touchpad, a variety of switches, a rocker input switch, etc. The composed data items input by the user may then be transmitted over the communication networks  319  via the transceiver module  311 .  
      When the mobile device  100  is operating in a voice communication mode, the overall operation of the mobile device is substantially similar to the data mode, except that received signals are preferably be output to the speaker  334  and voice signals for transmission are generated by a microphone  336 . Alternative voice or audio I/O subsystems, such as a voice message recording subsystem, may also be implemented on the mobile device  100 . Although voice or audio signal output is preferably accomplished primarily through the speaker  334 , the display  322  may also be used to provide an indication of the identity of a calling party, the duration of a voice call, or other voice call related information. For example, the microprocessor  338 , in conjunction with the voice communication module and the operating system software, may detect the caller identification information of an incoming voice call and display it on the display  322 .  
      A short-range communications subsystem  340  is also included in the mobile device  100 . The subsystem  340  may include an infrared device and associated circuits and components, or a short-range RF communication module such as a Bluetooth™ module or an 802.11 module, for example, to provide for communication with similarly-enabled systems and devices. Those skilled in the art will appreciate that “Bluetooth” and “802.11 ” refer to sets of specifications, available from the Institute of Electrical and Electronics Engineers, relating to wireless personal area networks and wireless local area networks, respectively.  
      The systems&#39; and methods&#39; data may be stored in one or more data stores. The data stores can be of many different types of storage devices and programming constructs, such as RAM, ROM, Flash memory, programming data structures, programming variables, etc. It is noted that data structures describe formats for use in organizing and storing data in databases, programs, memory, or other computer-readable media for use by a computer program.  
      The systems and methods may be provided on many different types of computer-readable media including computer storage mechanisms (e.g., CD-ROM, diskette, RAM, flash memory, computer&#39;s hard drive, etc.) that contain instructions for use in execution by a processor to perform the methods&#39; operations and implement the systems described herein.  
      The computer components, software modules, functions and data structures described herein may be connected directly or indirectly to each other in order to allow the flow of data needed for their operations. It is also noted that a module or processor includes but is not limited to a unit of code that performs a software operation, and can be implemented for example as a subroutine unit of code, or as a software function unit of code, or as an object (as in an object-oriented paradigm), or as an applet, or in a computer script language, or as another type of computer code.  
      Various embodiments of the present invention having been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention. The invention includes all such variations and modifications as fall within the scope of the appended claims.  
      A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by any one of the patent document or patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyrights whatsoever.