Message storage security system

A voice message system having a plurality of user voice mailboxes is disclosed. The voice message system utilizes a method in which a message is encrypted using a unique encrypting key corresponding to a designated user. The encrypted message is then stored in one location while the encrypting key is stored in another location. The encrypted message is retrieved by the designated user by utilizing a decrypting key which corresponds to the stored encrypting key. The decrypted message is then played by the designated user.

BACKGROUND OF THE INVENTION 
The present invention relates to a voice message system (VM System) and 
more particularly to a message storage security system for use in the VM 
System. 
In a voice message system (VM System), a calling party wishing to leave a 
message for another designated user, calls in to the VM System. The 
incoming voice message is digitized, stored on a disk, later retrieved by 
the designated user and converted back to voice. Most VM Systems enable 
several callers to transact with the system at the same time. When this 
happens, added measures are desirable to assure that message security is 
maintained. 
For example, when a designated user A signs on the system and tries to 
receive his messages, it is very important that that user A get his and 
only his messages. The integrity of message security is vulnerable if, for 
example, the VM System system should fail in the processing of updating 
pointers on the disk which identify a particular user's message as his. 
The messages typically are stored on disk memory, and directory entries 
are placed in a location assigned specifically to that user. The directory 
entries are stored both in random access memory (RAM) and on disk memory. 
Vulnerability occurs if, in the process of writing the directory to the 
disk memory, a system failure occurs. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an improved message 
storage security system for use in a voice message system. 
It is a more particular object of the present invention to provide for 
improved security so that a designated user of a VMS system has access to 
only his messages. 
It is a further object of the present invention to provide an improved 
security system that will provide security to messages stored in the VM 
System in the event of a system failure. 
Briefly, the invention provides for the unique encoding or encryption for a 
particular message for a designated user where the encoding key is stored 
on the designated user's message directory. For example, Message 1 for 
designated User A is scrambled using an encoding or encryption technique. 
The unique key that reverses the scrambling or encoding is stored on the 
user directory associated with Message 1 for designated User A. In a 
preferred embodiment, Message 2 for designated User A has a different 
encoding keythan for Message 1. 
In a preferred embodiment, the storage of the encoding key is the last item 
to be posted for the user directory. Consequently, a system failure can 
occur at any time without availing any user's message to anyone else. For 
example, if a system failure causes User B's directory to point to a 
message that in reality belongs to User A, the encoding key (or more 
properly decoding key) will be incorrect. Consequently, the message that 
is being fetched will not play. 
Similar protection is offered if the message disk should be copied and an 
attempt is made to play back all messages. It would then be necessary to 
know the encryption or encoding technique, which is stored in a different 
disk and processed with a separate circuit card than the card which 
processes disk activity. It would also be necessary to know which encoding 
and decoding keys are associated with which messages. This is a further 
security aspect of the present invention. 
In accordance with the foregoing summary, the present invention achieves 
the object of providing an improved message storage security system for 
use in a voice message system (VM System). Other objects, features and 
advantages of the present invention will become apparent from the 
following detailed description when taken in conjunction with the 
accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
Referring now to FIG. 1, a block diagram of a voice message system (VM 
System) is depicted. The present invention is incorporated into the VM 
System 10 of FIG. 1. 
VM System 10 of FIG. 1 is shown with system hardware components for 
purposes of providing a general description of a VM System system. A 
suitable VM System such as depicted in FIG. 1 is manufactured by Octel 
Communications Corporation of San Jose, Calif. However, the present 
invention would be applicable to other types of VM System as well. 
In FIG. 1, VM System 10 includes a CPU board 14 executes the operation 
system and the applications software. Typically, there are four serial I/O 
ports on CPU board 14 plus a standard disk interface to cartridge driver 
12. CPU board 14 also interfaces with a control bus 16 and a digital 
voice/data bus 18. CPU board 14 is electrically isolated from input 
signals from any I/O device by passing all external signals through 
light-emitting diodes (optical path). CPU 14 can manage over twenty-four 
separate transaction channels simultaneously. 
The file board 22 of FIG. 1 performs disk control functions for the 
Winchester drives 20. File board 22 also serves as a primary file manager 
in the system. File board 22 communicates with both CPU board 14 and line 
card 24. File board 22 handles both digitized voice and data and uses 
separate error correction and detection techniques for each, and is able 
to store both on the same disk. 
File board 22 has standard interfaces with Winchester disk drives 20, and 
is connected to control bus 16 and digital voice/data bus 18. 
Line card 24 of FIG. 1 has four channels, with each channel associated with 
a channel on a telephone interface card (TIC) 30. Only one TIC is 
associated with a line card 24. Line cards 24 are connected to control bus 
16 and to digital voice/data bus 18. Line card 24 performs the functions 
of voice digitizing; tone detection, including dual tone multifrequency 
(DTMF) detection; silence detection; automatic gain control and 
multiplexing. Also, line card 24 provides speed control over the speed of 
speech playback. 
The telephone interface card (TIC) 30 provides FCC-approved interfaces 
(Part 68) to either the public switched network (including Centrex) or to 
a customer's PBX. TIC 30 provides signaling detection; transformer 
isolation of various types such as Plain Old Telephone Service (POTS); tie 
trunk; DID trunk and integrated PBX. 
The scanner board 32 of FIG. 1 includes integral modems, an analog switch, 
an internal TIC function, a tone generator for testing, conference 
circuits and four serial I/O ports which optically connect to the serial 
I/O ports of CPU port 14. Winchester disk drive 20 of FIG. 1 stores system 
software, files and directories, digitized voice prompts and provides 
storage of digitized voice messages in personal greetings. 
Cartridge disk drive 12 of FIG. 1 accepts a 5-megabyte cartridge and 
provides software updates including new feature additions, system 
enhancements and the like. 
The digital voice/data bus 18 is a high speed serial bus used to transfer 
large amounts of both voice and data. Digitized voice can be sent at 
greatly accelerated speeds to buffers and played back at a listener's 
normal speed. 
Control bus 16 of FIG. 1 is a second high speed serial bus designed to 
automatically transfer small packets of control information. It processes 
large numbers of these packets while consuming very little overhead. 
The polling status control bus 34 of FIG. 1 interconnects the scanner board 
32 and TIC 30. Control bus 34 operates on a polled basis under control of 
scanner board 32. 
VM System 10 of FIG. 1 maintains a system directory (customer data base) of 
all user "mailboxes" with their associated class of service and associated 
passwords. There is no access to password information by a system manager 
or other technicians as the resident software makes passwords 
inaccessible. Every subscriber (user) has his own directory which contains 
information about messages in their "mailbox." VM System 10 of FIG. 1 also 
maintains message directories which tell where the various messages in the 
system are stored (i.e., which disk and where on each disk). All directory 
information is stored on both software/storage disks in disk drive 20 and 
cartridge disk drive 12. 
The hardware components of FIG. 1 have been described in order to simplify 
the description of the present invention, which is directed toward a 
message storage security system and which will now be described in detail 
in conjunction with FIGS. 2-4, taken with reference to the block diagram 
of FIG. 1. 
FIGS. 2A and 2B depict the sequence of events occurring externally to VM 
System 10 of FIG. 1. In FIG. 2A, a user will call in to the VM System of 
FIG. 1 and in normal operation the VM System answers, as indicated at step 
52. In typical VM System operation, the user (caller) records a message 
for deposit in a designated user's mailbox, as indicated in step 54 of 
FIG. 2A. VM System 10 of FIG. 1 stores the digitized message and makes a 
directory entry into the software as indicated by steps 56 of FIG. 2A. 
Subsequently, another user (the designated user) calls in to review any 
messages for him as indicated in FIG. 2B at step 60. The VM System answers 
the designated user's inquiry at step 62 and at step 64 the designated 
user identifies himself and enters his password into the VM System. 
At step 66, the designated user commands the VM System to present any 
messages for his review, and at step 68 the user listens to any messages. 
The sequence of events illustrated in FIGS. 2A and 2B is typical operation 
well known in VM Systems. 
Referring now to FIGS. 3A and 3B, the sequence of events occurring 
internally within VM System 10 of FIG. 1 is depicted. 
In FIG. 3A, the caller's voice is digitized by VM System 10 of FIG. 1. In 
step 70, the voice is digitized using a unique scramble code so that the 
message is scrambled, encoded or otherwise encrypted. The particular 
encoding technique could be any one of a number of well known techniques 
for encoding information. For purposes of this description, the term 
"encoded" is intended to encompass other similar terms such as 
"scrambling," "encrypting" and other known terms. Similarly, the 
corresponding "decoding" of a scrambled word is intended to include, in 
terms of meaning, "decrypting," "descrambling" and the like. 
In FIG. 3A, the encoded or scrambled message is stored by Vm System 10 of 
FIG. 1 in Winchester disk drive 20 (in typical operation). This is 
indicated by step 72. 
Also, in FIG. 3A, the encoded or scrambled code is set to the designated 
user's (recipient's) mailbox directory, and associated with the scrambled 
voice message on disk drive 20 of FIG. 1. This is indicated by step 74 of 
FIG. 3A. 
In FIG. 3B, the designated user desires to retrieve his messages and enters 
his mailbox number and password number into VM System 10 of FIG. 1, and 
then enters a command to review any messages waiting for him. This is 
indicated by step 80. Subsequently, at step 82, VM System 10 of FIG. 1 
"attaches" the scrambled code to a channel to connect the message to the 
user. At step 84, the scrambled encoded message is retrieved from disk 
drive 20 and played through the channel with the scrambled code. This is 
indicated in step 84. 
One important note is that if any disk errors occur or the system retrieves 
an incorrect message, the scrambled code in the channel will not be 
unscrambled, and consequently there will not be any playing of 
unauthorized voice messages to a non-designated user. This is a security 
aspect of the present invention. 
Referring now to FIG. 4A, the sequence of events occurring in conjunction 
with the telephone line controller of FIG. 1 is depicted. 
In FIG. 4A, line card circuit 24 of FIG. 1 adds a scramble code and 
digitizes the voice message, as indicated at step 90. 
At step 92, line card circuit 24 passes the scrambled digitized voice to 
file board circuit 22. This is indicated at step 92. 
Line card circuit 24 of FIG. 1 also passes the actual scramble code to file 
card circuit 22, as indicated at step 94 of FIG. 4A. 
Finally, disk drive 20 of FIG. 1 receives the scrambled voice and the 
encoded message is stored in disk drive 20 of FIG. 1. 
Similarly, as indicated by step 98, the scrambled code is filed in a user 
message directory. 
FIG. 4B illustrates the sequence of events occurring when the user is 
obtaining his message for playback. In FIG. 4B, file card circuit 22 
responds to the request for scrambled voice message, as indicated by step 
100, and retrieves the scrambled voice message from disk drive 20, as 
indicated by step 102. 
At step 104, the retrieved message is played back through line card circuit 
24 of FIG. 1. 
Step 106 of FIG. 4B illustrates that file card 22 requests the scramble 
code from the user message directory. 
At step 108, the scrambled code is retrieved from disk drive 20, and at 
step 110 the scrambled code is assigned to the same channel as the 
scrambled message via line card 24. 
Finally, at step 112, the unscrambled voice message is available through 
line card 24 to telephone interface card 30 for playback to the designated 
user via analog voice line 36 of FIG. 1. 
As can be seen from the foregoing description, a message storage security 
system for use in a voice message system has been described. The technique 
and method described herein provide improved security aspects in a voice 
message system. The security provided only permits a designated authorized 
user to have access to his or her recorded messages by using encoding or 
scrambling techniques in a particular fashion. Also, in the event of a 
system failure, such as when a user's directory points to a different user 
because the encoding keys are totally different, there is no unauthorized 
playback of a particular message. 
It is therefore intended that the scope of the present invention only be 
limited by the appended claims.