Cryptography – Key management
Reexamination Certificate
1998-09-23
2001-04-10
Barron, Jr., Gilberto (Department: 2767)
Cryptography
Key management
C380S279000, C380S282000, C713S163000, C713S171000, C713S152000
Reexamination Certificate
active
06215877
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a chat system for performing the communication real time using a character or the like, a chat system terminal unit, a key management server for supplying a key to the encryption of the communication, and a recording medium readable between computers on a computer network such as the internet or the intranet.
FIG. 1
is a diagram for explaining the principle of a conventional chat system. In this chat system, communication channels A to C (
51
to
53
) are opened on a chat server
50
connected to a computer network. The user connects the chat server
50
by chat clients (terminal units)
60
to
69
and thus selectively connects the channels A to C (
51
to
53
). As a result, the communication using a character or the like can be accomplished between users connected to the same channel. Generally, the information transmitted from a user is distributed to all the users connected to the same channel. Also, even on a channel connected with three or more users, one-to-one communication between users is possible.
FIG. 2
is a block diagram showing a configuration example of the essential parts of the conventional chat system. In this chat system, first, an input unit
14
of a chat client
5
receives an input signal from a keyboard (not shown). In
FIG. 2
, only a single chat client
5
is shown as a representative. An input signal received by the input unit
14
is transmitted by a transmission section
16
to a channel X(
4
) which, in the chat server
2
is selected by a channel selection section
10
. A signal arriving from other chat clients through the channel X(
4
) in the chat server
2
is received by a receiving section
17
. The signal received by the receiving section
17
is output by an output unit
19
to and is displayed on a display screen (not shown).
In this chat system, the communication between the chat client and the chat server is carried out in a plaintext and therefore a communication text is liable to be eavesdropped midway of the communication line.
A method suggested for preventing the eavesdropping is to encrypt the communication text using a secret key prepared by a chat server.
FIG. 3
is a block diagram showing an example configuration of the essential parts of a conventional chat system with the communication text encrypted. The chat server
7
of the chat system includes a channel secret key generation section
34
, an encryption section
33
, a channel secret key request receiving section
31
and a channel secret key distribution section
32
. The channel secret key generation section
34
generates a channel secret key unique to each channel for encrypting/decrypting the communication data exchanged through a channel in the server
7
managed by the server
7
. The encryption section
33
encrypts the channel secret key generated by the channel secret key generation section
34
. The channel secret key request receiving section
31
receives a distribution request of the channel secret key unique to the channel X(
4
) from a chat client
6
through the channel X(
4
). When the channel secret key request receiving section
31
receives the distribution request, the channel secret key distribution section
32
distributes the channel secret key unique to the channel X(
4
) encrypted by the encryption section
33
to the chat client
6
through the channel X(
4
). In
FIG. 3
, only one chat client
6
is shown to represent all chat clients.
The chat client
6
of the chat system includes a channel selection section
10
for selecting a connected channel, a channel secret key request section
11
for requesting a channel secret key unique to the channel X(
4
) through the channel X(
4
) selected by the channel selection section
10
, a channel secret key receiving section
12
for receiving the channel secret key requested by the channel secret key request section
11
, a channel secret key decryption section
13
for decrypting the channel secret key received by the channel secret key receiving section
12
, and an input unit
14
for receiving the input signal from a keyboard (not shown).
The client
6
of the chat system includes an encryption section
15
for encrypting the input signal received by the input unit
14
using the channel secret key decrypted by the channel secret key decryption section
13
, a transmission section
16
for transmitting the input signal encrypted by the encryption section
15
to the channel X(
4
), a receiving section
17
for receiving the signal arriving from other channel clients through the channel X(
4
), a decryption section
18
for decrypting the signal received by the receiving section
17
using the channel secret key, and an output unit
19
for outputting and displaying the received signal decrypted by the decryption section
18
in the form of character on a display screen (not shown).
With the chat system having this configuration, the chat server
7
generates a secret key of each channel at the channel secret key generation section
34
and encrypts the channel secret key at the encryption section
33
.
The chat client
6
selects the connected channel at the channel selector
10
, and the channel secret key request section
11
requests the chat server
7
for a channel secret key unique to the channel X(
4
) through the channel X(
4
) selected by the channel secret key request section
11
. The chat server
7
accepts the request at the channel secret key request receiving section
31
and distributes the encrypted channel secret key unique to the channel X(
4
) to the chat client
6
through the channel X(
4
).
The chat client
6
receives the requested channel secret key unique to the channel X(
4
) at the channel secret key receiving section
12
, and decrypts the received channel secret key at the channel secret key decryption section
13
. The chat client
6
encrypts/decrypts the signal transmitted/received to and from the channel X(
4
) at the encryption section
15
/decryption section
18
using the decrypted channel secret key.
In the above-mentioned chat system, however, the communication text on the chat server
7
can be modified into a plaintext and eavesdropped by reconstructing the chat server
7
. Even when the plaintext is encrypted by the secret key prepared by the chat server, therefore, the likelihood of eavesdropping is not eliminated.
BRIEF SUMMARY OF THE INVENTION
The present invention is intended to solve the above-mentioned problems and the object thereof is to provide a key management server, a chat system terminal unit, a chat system and a recording medium for realizing the chat system and the terminal unit thereof which are capable of keeping a communication secret even in the case where the chat server is low in reliability.
According to the present invention, there is provided a key management server comprising means for generating a channel secret key unique to each channel for encrypting/decrypting the communication data exchanged through a plurality of channels managed by one or more chat servers, means for encrypting the channel secret key generated by the channel secret key generation means, means for receiving the distribution request of the channel secret key unique to a channel through the channel managed by the chat server from a second terminal unit, and means for distributing the channel secret key unique to the channel encrypted by the encryption means to the second terminal unit through the same channel.
In view of the fact that like the chat client, the key management server constituting a terminal unit as viewed from the chat server generates a channel secret key unique to each channel, the communication can be kept secret even when a chat server low in reliability is used.
Also, in the key management server according to this invention, the channel secret key generation means generates the channel secret key unique to each of the groups which is divided so as to include a plurality of terminal units in the channel, and the receiving means receives the distribution request for the channe
Barron Jr. Gilberto
Fujitsu Limited
Staas & Halsey , LLP
LandOfFree
Key management server, chat system terminal unit, chat... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Key management server, chat system terminal unit, chat..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Key management server, chat system terminal unit, chat... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2462861