FIELD OF THE INVENTION
The invention relates in general to electronic systems for safe exchange of electronic information between computer networks and in particular to a secured transfer system (STS) between a private network and a public network. The private network can be a real private network (RPN) or integrated real private network (IRPN) of an organisation and public networks can be networks like the Internet. It facilitates free exchange of electronic information, data, and mail between and, without compromising the security of the former (i.e. RPN or IRPN).
BACKGROUND AND PRIOR ART
Private networks for multi-location organisations have become a must for reasons of security, in the wake of enterprise-wise computerisation and computing across geographically separated locations.
The VPN or virtual private network is a poor substitute for RPN or real private network which ensure 100% security, achieved by point-to-point leased lines between organisation locations, and there is growing realisation of this fact.
While on one hand, for reasons of security, RPNs are required to ensure safety of organisational data bases in the process of WAN computing, on the other hand, organisations and enterprises have to be a part of the Global Information Highway, which is the Internet, and make all its publishable information available to the business community and the general public to facilitate the emerging e-Commerce activity. Such exchanges of electronic data must therefore be secured.
In the present state-of-the art, the security requirement is met predominantly through
either various software firewalls, or through software firewalls aided by router access
controls etc.
However, the systems in the prior art are not able to deny telnet access from the public
telephone networks to the real private networks (RPN or IRPN), thereby leaving the
networks unsafe to a large extent.
The present invention seeks to overcome this and other drawbacks of the prior art.
OBJECTS OF THE INVENTION
Therefore the primary object of the present invention is to provide a system that ensures secured exchange of electronic data between different networks and also ensures that there is no telnet access from the Internet LAN to the real private network LAN of an organisation.
Another object of the invention is to provide a cost-effective system that secures data stored in an organisation's private network while sharing them with the Internet.

Yet another object of the invention is to provide a system that secures an organisation's data during e-commerce processes.
How the foregoing objects are achieved will be clear from the following description. In this context it is clarified that the description provided is non-limiting and is only by way of explanation of the invention.
SUMMARY OF THE INVENTION
A secured transfer system (STS) between a private network and a public network comprises of at least one company proxy mail server and at least one company proxy web server which are connected to an internet LAN. It has at least one electromechanical three-way switch, one end of which is permanently connected to the LAN card of an intermediate server and the other two ends are optionally connected to either the internet LAN or the company real private network LAN respectively. It also has at least one company mail server and a plurality of company servers which are connected to INTRANET (RPN) LAN.
The electromechanical switch physically separates the Internet from the real private network (RPN) of an organisation by creating an air gap between the Internet and the enterprise/organisation RPN and yet allows free exchange of information/data/mail between the two networks.
A second electromechanical switch is connected to LAN card of associated Internet-browsing nodes and the other end of the switch is connected to either the internet LAN or the company real private network LAN.
Thus, it ensures that there is no telnet access from the Internet LAN to the RPN LAN, thereby ensuring total security of the RPN LAN while allowing free exchange of data between the two. Moreover, it gives the enterprise/organisation the facility for e-Commerce without compromising the security of its internal data bases.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The nature and scope of the present invention will be better understood from the accompanying drawings, which are by way of illustration of a preferred embodiment and not by way of any sort of limitation. In the accompanying drawings:-
Figure 1 is a schematic representation of the method of connecting an organisation's LANs / WAN to the Internet according to the prior art.
Figure 2 is a schematic representation of the method of Internet connection to company LAN according to the present invention.
Figure 3 shows how computers in the company location may connect either to the Internet LAN or the Company LAN using the invented system.
Figure 4 is a schematic representation of the invented Secured Transfer System (STS).

Figure 5 shows the data flow through the Secured Transfer System (STS) according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Having described the main features of the invention above, a more detailed and non-limiting description of a preferred embodiment will be given in the following paragraphs with reference to the accompanying drawings. In all the figures, like reference numerals represent like features.
The stated objects are met by this invention which provides a Secured Transfer System (STS) between a private network and a public network for transferring information, data, and mail back and forth between the 100% secure real private networks (RPNs) of the enterprise / organisation and the open public information highway - the Internet. The following description explains how it is done.
Figure 1 shows an arrangement of connection of company LAN to the Internet according to the prior art. Here, the company has own mail and WEB servers with authentication which receive all incoming mails. Company LAN members must access their mails from this server through leased lines. The company's own mail and WEB servers are connected to the Internet hub through a gateway router, which is also connected to public subscriber telephone networks (PSTN), thereby compromising the security of the stored data in company servers.
Reference is now made to figures 2 and 4. Figure 2 shows the connection scheme deploying the secured transfer system (STS) according to this invention, while figure 4 shows the layout of the physical connections between its components. All the information which the enterprise/organisation wants to publish is loaded onto a proxy server (3), also referred as PS. This server is connected to the Internet LAN bus (2) in the company premises. The proxy server (3) has two primary functions.
A. To display all publishable information of the enterprise/organisation, to
which everybody logging in will have read-only access.
B. To have WEB-based interactive screens through which outsiders to the
organisation may transact business e.g. submit offers, place orders, exchange
information of mutual benefit, etc.
The proxy server (1) has the following functions.
C. To receive and send mails from the employees of the organisation to
outsiders of the organisation, and act as the organisation's Internet Mail
Gateway.

A company server (9), also called CS, is connected to the RPN LAN bus (6) in the organisation's premises and has fields identical to those of the proxy servers (1, 3). These are fields which are updated continuously from the other data base servers (10, 11) connected to the RPN LAN bus (6) of the organisation.
An Intermediate Server (4), also called IS and best shown in figure 5, which has the same fields as the proxy servers (1, 3) and the company server (9), connects periodically (settable) to either proxy servers (1 or 3) or the company server (9) to synchronise information/data/ mail with these servers, both ways.
One end of an electro-mechanical three-position switch (5) is permanently connected to the LAN card of the intermediate server (4). This switch connects the IS either to the Internet LAN bus (2) or the RPN LAN bus (6), but never to both together. The switch also has a null position in which state the IS LAN card is not connected to either of the LAN buses (the Internet or RPN LAN buses). In this null state, a cleansing software residing in the intermediate server (4) cleans the content from viruses, worms, etc. which may have come from either of the LAN buses (Internet or RPN) during the last connect period, before transferring the information/data/mail to either server (1, 3) or server (9) through their respective LAN buses. The cleansing software patches are updated every time the IS (4) connects to the Internet LAN bus (2).
The change-of-state commands for the three position switch (5) also reside in the IS and are given through the serial ports of the IS and the switch.
Reference is now made to figure 3 which shows the connections of three-way switch (5). The three-way LAN switch (5) is an Ethernet change-over switch with a null state. It needs some ASCII characters through the serial port of the computer to change its state. The commands could be simple like
Command -IN, Action : Connect to internal network
Command - EX, Action : Connect to proxy server
Command - NC, Action : Connect to None
For the switch connected to intermediate server (4), the commands are initiated by this computer based on a time period which is settable. The dwell period in the null state is also settable, and is sufficient to clean the data received from the Internet from viruses before connecting to the company LAN.
For the switch (7) connected to the Internet-browsing nodes (8), the commands are manual. The software provides an interlock which prevents change-over from null state to company LAN connection before the node has been thoroughly cleaned, after being connected to the Internet.
The switch (7), which too is an electromechanical tree-way switch similar to switch (5), may additionally be used to connect a node computer in an organisation location or

employee's work place either to the Internet LAN bus or the RPN LAN bus through the respective I/O boxes placed at the location. This is best shown in figure 3.
The null position of the switch and the preselected dwell time in this position ensures that the node computer may not connect to either LAN bus, before it is properly cleansed from viruses/worms/etc., through a built-in cleansing software. The cleansing software patches are updated every time the node computer connects to the Internet LAN bus.
Whereas the change-of-state commands for the IS are settable and automatic, the change-of-state commands for the node computers are given through manual ASCII commands.
Figure 5 shows the data flow through the STS according to the invention. The data flow for all publishable information is unidirectional from company server (10) to IS (4) to web server (3) as shown in this diagram. The WEB based inputs of information/ submissions on the interactive screens are unidirectional from web server (3) to IS (4) to company server (11) as shown. The email flows are however bidirectional from PS (1) to IS (4) to CS (9) to IS (4) to PS (1), also shown here.
Movement of data through the STS according to the present invention is given in details below.
1. All mail for the company from the Internet arrives at the company proxy mail server (1) connected to the Internet.
2. This data is exchanged with the outgoing mail residing in the Intermediate Server IS (4) at the time when the latter is connected to the Internet LAN.
3. The incoming mail gets transferred to the company mail server (9), best shown in figure 2, which is connected to the RPN LAN (6) at the time the IS (4) connects to the RPN LAN (6) bus. At this time all mails meant for outsiders get transferred to the IS.
4. The movement of mail between the company proxy mail server (1) and the company mail server (9) is bidirectional through the IS (4).
5. Individual mail box owners can access their mail boxes through the CMS (9) through the RPN LAN (6)/WAN as best shown in Fig. 4, both for internal and external mails. The internal mail is never moved to the CPMS (1) through IS (4).
6. The company proxy WEB Server (3) which is connected to the Internet LAN (2) has a read only section which contains the company's publishable information, and is periodically updated from the company servers (10, 11). The movement of information is unidirectional as shown in figure 5. The data contained in this section cannot be tampered with by outsiders accessing the WEB server.

7. A second section of the WEB server (3) is provided with interactive screens which
are adapted to support the company's e-Commerce and e-Business activity. The data/ inputs received in this section from the clients/vendors on the Internet are moved to the company servers (10, 11) connected to the RPN LAN (6). This data too moves in a unidirectional mode from server (3) connected to Internet LAN, to IS (4) to servers (10, 11), connected to RPN LAN.
In this manner, free flow of information is conducted between the Internet LAN and the RPN LAN, but without any compromise of security of the RPN LAN and the data bases connected to it.
The principal aim of the STS described above is to ensure that there is no telnet access from the Internet LAN to the RPN LAN. This is achieved by the air gap created by the electromechanical three position switch (5).
This system does not allow browsing of Internet from the RPN LAN bus (6). Those within the company, who are authorised to avail Internet browsing facility, are provided with a separate I/O box for the Internet LAN at their location. One end of switch (7) is then connected to the LAN card of the particular node computer (8), which also connects to the two I/O boxes from the Internet LAN and the RPN LAN. The switch (7) ensures a forced null period to cleanse the node (8) with the help of a cleansing software loaded on the node computer, before connecting either to the RPN or the Internet LAN. The switch also ensures that the node computer cannot be connected to both LANs together.
ADVANTAGES
The principal technical advantage achieved by the present invention is that the electromechanical switch (5) ensures that there is no telnet access from the Internet LAN (2) to the RPN LAN (6) by physically separating the Internet from the RPN by creating an air gap, thereby providing total security of the RPN LAN (6) while allowing free exchange of data between the two.
The non-limiting advantages of the present invention, the secured transfer system (STS), are as follow.
a. It facilitates free flow of information/data/mail between the company RPN and
the Internet.
b. It ensures that there is no telnet access from outsiders of the organisation to the
organisation's RPN LAN and the data bases that are connected to it.
c. It ensures 100% security of the RPN LAN and the data bases connected to it.
d. It physically separates the Internet from the real private network (RPN) of an
organisation by creating an air gap between the Internet and the enterprise/
organisation RPN and yet allows free exchange of information/data/mail between
the two networks.

r
e. It gives the enterprise/organisation the facility for e-Commerce without
compromising the security of its internal data bases.
f. It removes all major impediments to the growth of e-Business, namely the
security concerns for internal data bases of the enterprise/organization.
The present invention has been described with reference to some drawings and a preferred embodiment purely for the sake of understanding and not by way of any limitation and the present invention includes all legitimate developments within the scope of what has been described herein before and claimed in the appended claims.

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I claim:
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1. A secured transfer system (STS) between a private network and a public network comprising of at least one company proxy mail server (1) and at least one company proxy web server (3) connected to an internet LAN (2), characterized in that there is a first electromechanical three-way switch (5),
15 which is permanently connected to the LAN card of an intermediate server (4)
at one end and the other end of said switch is connected to either the internet LAN (2) or the company real private network LAN (6), and in that one end of at least a second electromechanical switch (7) is connected to LAN card of associated Internet-browsing nodes (8) and the
20 other end of the switch is connected to either the internet LAN (2) or the
company real private network LAN (6),
and at least one company mail server (9) and a plurality of company servers (10,11) are connected to the company real private network LAN (6).
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ASBTRACT

A Secured Transfer System (STS) Between A Private Network And A Public Network
A secured transfer system (STS) has company proxy mail server (1) and company proxy web server (3) connected to an internet LAN (2), one end of a first electromechanical three-way switch (5) is connected to intermediate server (4) and the other end is connected to either internet LAN (2) or company network LAN (6). One end of a second electromechanical switch (7) is connected to associated Internet-browsing nodes (8) and the other end is connected to either LAN (2) or LAN (6). A company mail server (9) and company servers (10,11) are connected to LAN (6).
The electromechanical switch (5) ensures no telnet access from the Internet LAN (2) to the RPN LAN (6) by physically separating the Internet from the RPN by creating an air gap, thereby providing total security of the RPN LAN (6) while allowing free exchange of data between the two.