United States Patent r19J
`Ueno et al.
`
`I 1111111111111111 11111 111111111111111 IIIII IIIII IIIII lllll 111111111111111111
`US005574785A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,574,785
`Nov. 12, 1996
`
`[54] ENCIPHERED COMMUNICATION SYSTEM
`
`[75]
`
`Inventors: Tomoyuki Ueno; Mitsuru Seta, both of
`Kawasaki, Japan
`
`3,538,242
`5,297,208
`5,392,352
`5,432,848
`
`11/1970 Hepner .................................. 380/20 X
`3/1994 Schlafly et al. ........................... 380/49
`2/1995 Han ......................................... 380/9 X
`7/1995 Bulter et al ................................. 380/2
`
`[73] Assignee: Fujitsu Limited, Kanagawa, Japan
`
`(21] Appl. No.: 365,915
`Dec. 29, 1994
`
`(22] Filed:
`
`[30]
`
`Foreign Application Priority Data
`
`[JP)
`
`Japan .................................... 6-117828
`May 31, I 994
`[51) Int. Cl.6
`............ ............................... ......... .... H04L 9/00
`[52J U.S. Cl . ..................................... 380/2; 380/9; 380/21;
`380/49
`(58] Field of Search ............................... 380/2, 9 , 20, 21,
`380/28, 48, 49
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`Primary Examiner-Bernarr E. Gregory
`
`[57]
`
`ABSTRACT
`
`An enciphered communication system is provided which has
`a plurality of cipher keys selectively used for enciphering
`data, wherein even when a cipher key number used at a
`transmitting side is not correctly transmitted to a receiving
`side, the receiving side can change the cipher key to a correct
`one. A transmitter has appendant data affixing means for
`affixing appendant data to information to be enciphered, and
`a receiver has appendant data detecting means for detecting
`the appendant data from deciphered data, and cipher key
`determining means for successively changing the cipher key
`of the receiver when the appendant data is not accurately
`detected. Consequently, when the cipher key is changed, for
`example, the receiving side itself can restore data even if the
`cipher key number is not correctly transmitted thereto.
`
`3,244,806
`3,466,385
`
`4/1966 Morris ................................... 380/20 X
`9/1969 Hendrickson ......................... 380/20 X
`
`13 Claims, 17 Drawing Sheets
`
`\ 10 0 TRANSMITTER
`
`\ 200 RECEIVER
`
`( 201
`
`( 202
`
`IN
`
`APPENDANT
`PUT DATA ,_ - DATA AFFIX-
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`-
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`IO I
`
`162
`
`2J3
`
`CIPHER KEY
`DETERMINING
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`
`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0001
`IPR2020-00614 (Netflix, Inc. and Hulu, LLC v. DivX, LLC)
`
`

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`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0002
`IPR2020-00614 (Netflix, Inc. and Hulu, LLC v. DivX, LLC)
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`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0003
`IPR2020-00614 (Netflix, Inc. and Hulu, LLC v. DivX, LLC)
`
`

`

`U.S. Patent
`
`Nov. 12, 1996
`
`Sheet 3 of 17
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`5,574,785
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`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0004
`IPR2020-00614 (Netflix, Inc. and Hulu, LLC v. DivX, LLC)
`
`

`

`U.S. Patent
`
`Nov. 12, 1996
`
`Sheet 4 of 17
`
`5,574,785
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`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0005
`IPR2020-00614 (Netflix, Inc. and Hulu, LLC v. DivX, LLC)
`
`

`

`U.S. Patent
`
`Nov. 12, 1996
`
`Sheet 5 of 17
`
`5,574,785
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`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0006
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`
`

`

`U.S. Patent
`
`Nov. 12, 1996
`
`Sheet 6 of 17
`
`5,574,785
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`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0007
`IPR2020-00614 (Netflix, Inc. and Hulu, LLC v. DivX, LLC)
`
`

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`
`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0008
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`
`

`

`U.S. Patent
`
`Nov. 12, 1996
`
`Sheet 8 of 17
`
`5,574,785
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`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0009
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`
`

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`
`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0010
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`
`

`

`U.S. Patent
`
`Nov. 12, 1996
`
`Sheet 10 of 17
`
`5,574,785
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`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0011
`IPR2020-00614 (Netflix, Inc. and Hulu, LLC v. DivX, LLC)
`
`

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`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0012
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`
`

`

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`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0013
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`
`

`

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`-llllllllllf I-II Ill!! l-llllllllllll-llllllllllll-llllllllllllllllllllllll-llll-llllllllllll ~111-1111-llllllllllll ~11111111111-
`
`Fl G.130 R.;oro t·J.?1.VE
`
`k--ENCIPHERED~ ~ENCIPHERED~ k--ENCIPHERED~
`-----~-·------------
`
`-------· -
`
`F IMAGE DATA -1 CHK F IMAGE DATA -2 CHK F IMAGE DATA -3 CHK
`
`ENCIPHERED DATA
`
`FIG.I3C
`
`F IMAGE DATA -3
`
`F IMAGE DATA -2
`
`F IMAGE DATA -1
`
`VIDEO DATA
`DIGITAL COMPRESSED
`
`FIG.I38
`
`ANALOG VIDEO SIGNAL
`
`FIG.I3A
`
`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0014
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`
`

`

`~ ... ....;a
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`T RANSMIT SIGNAL
`
`SECTION
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`DAT.!\.
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`CODING SECTION
`ERROR-DETECTION
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`(533
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`TABLE
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`NUMBER
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`
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`CIPHER KEY
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`
`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0015
`IPR2020-00614 (Netflix, Inc. and Hulu, LLC v. DivX, LLC)
`
`

`

`01
`~
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`DATA
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`
`SECTION
`DETECTING
`ERROR
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`DATA DECIPHER
`
`-
`
`SIGNAL
`RECEIVED
`
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`
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`
`CIRCUIT
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`NUMBER
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`l
`
`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0016
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`
`

`

`tll
`00
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`RECEIVING
`NUM.BER
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`
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`
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`
`(21
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`
`PRIOR ART
`
`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0017
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`
`

`

`U.S. Patent
`
`Nov. 12, 1996
`
`Sheet 17 of 17
`
`5,574,785
`
`LL
`
`I
`
`Cl
`[i]
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`
`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0018
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`
`

`

`5,574,785
`
`1
`ENCIPHERED COMMUNICATION SYSTEM
`
`BACKGROUND OF THE INVENTION
`
`5
`
`2
`mission line 3 from the transmitter 1 consists of input data
`D enciphered by the data enciphering section 11, the cipher
`key number N(ks) output from the cipher key number
`sending section 14 and multiplexed at the multiplexing
`section 15, and frame synchronizing signals F. The cipher
`key number N(ks) is usually transmitted only when it bas
`been changed; in some cases, the cipher key number is
`transmitted at the start of data communication or at regular
`intervals, or is transmitted with each of frames.
`ln the conventional enciphered commurucation system
`having a plurality of cipher keys, information about the
`cipher key number is transmitted from the transmitter to the
`receiver. Thus, if one of data items relating to the cipher key
`number, among the information transmitted when the cipher
`key number is changed, is accidentally in error, for example,
`all the other received data becomes erroneous because the
`receiver deciphers the received data by means of the cipher
`key corresponding to the previously notified cipher key
`number, making normal deciphering impossible. In such
`cases, moreover, received data continues to become errone(cid:173)
`ous until the cipher key_ number is correctly notified.
`In the case of a two-way communication system, retrans(cid:173)
`mission of the cipher key number can be requested upon
`detection of discrepancy between the cipher key numbers.
`However, in a one-way communication system such as a
`broadcasting system which allows no such retransmission
`request, received data continues to become erroneous until
`the cipher key number is correctly notified.
`
`SUMMARY OF THE INVENTION
`
`(1) Field of the Invention
`The present invention relates to an enciphered communi(cid:173)
`cation system, and more particularly, to a system for enci(cid:173)
`phered communications in a data communication system
`wherein a plurality of cipher keys are used for enciphering 10
`data and are switched as required.
`(2) Description of the Related Art
`Conventionally, measures arc taken to encipher secret
`data before transmission so that the contents of the data may
`be unintelligible even if intercepted during transmission via 15
`a communication line. Enciphering methods include DES
`(Data Encryption Standard) and FEAL (Fast data Enciphcr(cid:173)
`ment ALgorithm) using secret or publicly open cipher keys,
`and an identical cipher key is used at transmitting and
`receiving sides to accomplish normal data communications. 20
`FIG. 16 illustrates the configuration of a conventional
`enciphered communication system. As shown in FIG. 16,
`the conventional enciphered communication system com(cid:173)
`prises a transmitter 1 for enciphering and transmitting data,
`and a receiver 2 for receiving and deciphering the enci- 25
`phered data. A transmission line 3 connecting the transmitter
`1 and the receiver 2 is not particularly limited, and may be
`of a wired type such as a telephone line or a wireless type
`as used in communications utilizing a satellite. FIG. 16
`illustrates only the enciphering/deciphering-related parts of 30
`the transmitter 1 and the receiver 2.
`The transmitter 1 includes a data enciphering section 11
`for enciphering input data by means of a cipher key ks, a
`cipher key table 12 for converting a specified number N(ks)
`to a cipher key ks, a cipher key number setting section 13 for
`setting a number N(ks) by which a cipher key k~ in the
`cipher key table 12 is selected to be used for enciphering the
`input data, a cipher key number sending section 14 for
`sending the cipher key number N(ks) selected by the cipher
`key number setting section 13 to the receiver 2, and a
`multiplexing section 15 for multiplexing the enciphered data
`and the cipher key number N(ks).
`The receiver 2 includes a separating section 21 for receiv(cid:173)
`ing data transmitted via the transmission line 3 and sepa(cid:173)
`rating the received data into enciphered data and a cipher
`key number, a cipher key number receiving section 22 for
`receiving the separated cipher key number, a cipher key
`table 23 having the same contents as the cipher key table 12
`of the transmitter 1, and a data deciphering section 24 for 50
`deciphering the separated enciphered data by means of a
`cipher key ks specified by the cipher key number N(ks)'.
`Thus, the transmitter 1 and the receiver 2 have identical
`cipher key tables 12 and 23, respectively, each having a
`plurality of cipher keys, and only the cipher key number
`corresponding to the cipher key which is used to encipher
`the transmit data is transmitted to the recci ver 2. The
`receiving side decodes the received data to acquire the
`cipher key number, and obtains the same cipher key as used
`at the transmitting side from the cipher key number to
`decipher the enciphered data. This arrangement permits the
`cipher key number to be changed as needed, and also
`ensures high-secrecy transmission because the cipher key
`itself is not transmitted.
`FIG. 17 schematically illustrates data on a transmission 65
`line of the conventional enciphered communication system.
`As shown in FIG. 17, the data transmitted onto the trans-
`
`40
`
`45
`
`One object of the present invention is to provide an
`enciphered communication system which uses a plurality of
`cipher keys and which is capable of changing an erroneously
`35 notified cipher key number to a correct cipher key number
`in cases where the cipher key number is transmitted only
`infrequently, for example, at the time when the cipher key is
`changed.
`Another object of the present invention is to provide an
`enciphered communication system wherein a receiving side
`can find the same cipher key number as used at a transmit(cid:173)
`ting side even in cases where the cipher key number itself is
`not transmitted and, when the cipher key is changed, the
`receiving side follows such change and obtains the same
`cipher key number as used at the transmitting side.
`Still another object of the present invention is to provide
`an enciphered communication system in which all transmit(cid:173)
`ted data can be received without any error being caused.
`To achieve the above objects, there is provided according
`to the present invention an enciphered communication sys(cid:173)
`tem having a plurality of cipher keys to be switched as
`required. The enciphered communication system comprises
`a transmitter including appendant data affixing means for
`55 affixing appendant data to input data to be enciphered, and
`enciphering means having a plurality of cipher keys selec(cid:173)
`tively used for enciphering the input data and the appendant
`data output from the appendant data affixing means, and a
`receiver including deciphering means for deciphering the
`60 enciphered data received via a transmission line, appendant
`data detecting means for detecting the appendant data
`affixed to the input data, and cipher key determining means
`for determining whether a cipher key used for the decipher-
`ing is correct, based on · an error rate of the detected
`appendant data, and for instructing the deciphering means to
`change the cipher key used for the deciphering when it is
`judged that the cipher key is not correct.
`
`Netflix, Inc. and Hulu, LLC - Ex. 1004, Page 0019
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`

`

`5,574,785
`
`3
`The above and other objects, features and advantages of
`the present invention will become apparent from the fol(cid:173)
`lowing description when taken in conjunction with the
`accompanying drawings which illustrate preferred embodi(cid:173)
`ments of the present invention by way of example.
`
`BRIEF DESCRJPTION OF THE DRAWINGS
`FIG. 1 is a diagram illustrating the principles of the
`present invention;
`FIG. 2 is a diagram illustrating the configuration of an
`enciphered communication system according to a first
`embodiment of the present invention;
`FIG. 3 is a diagram showing an example of the arrange(cid:173)
`ment of a cipher key determining section;
`FIG. 4 is a diagram schematically showing data on a
`transmission line of the enciphered communication system
`according to the first embodiment;
`FIG. 5 is a diagram illustrating the configuration of an
`enciphered communication system according to a second
`embodiment of the present invention;
`FIG. 6 is a diagram schematically showing data on a
`transmission line of the enciphered communication system
`according to the second embodiment;
`FIG. 7 is a diagram illustrating the configuration of an
`enciphered communication system according to a third
`embodiment of the present invention;
`FIG. 8 is a diagram schematically showing data on a
`transmission line of the enciphered communication system
`according to the third embodiment;
`FIG. 9 is a diagram illustrating the configuration of an
`enciphered communication system according to a fourth
`embodiment of the present invention;
`FIG. 10 is a diagram schematically showing data on a
`transmission line of the enciphered communication system
`according to the fourth embodiment;
`FIG. 11 is a diagram illustrating the configuration of an
`enciphered communication system according to a fifth
`embodiment of the present invention;
`FIG. 12 is a diagram showing an example wherein the
`enciphered communication system of the present invention
`is applied to digital image broadcasting;
`FIG. 13 is a chart schematically showing data at various
`parts in a digital image broadcasting system;
`FIG. 14 is a diagram showing an example of the arrange(cid:173)
`ment of a transmitting-side enciphering device in the digital
`image broadcasting system;
`FIG. 15 is a diagram showing an example of the arrange(cid:173)
`ment of a receiving-side enciphering device in the digital
`image broadcasting system;
`FIG. 16 is a diagram illustrating the configuration of a
`conventional enciphered communication system; and
`FIG. 17 is a diagram schematically showing data on a
`transmission line of the conventional enciphered communi(cid:173)
`cation system.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIME!\1TS
`
`Embodiments according to the present invention will be
`described in detail.
`FIG. 1 is a diagram illustrating the principles of the
`present invention. In an enciphered communication system
`according to the present invention, a transmitter 100 com-
`
`25
`
`4
`prises appendant data affixing means 101 for affixing appcn(cid:173)
`dant data to input data to be enciphered, and enciphering
`means 102 for enciphering each of the input data and
`appendant data output from the appendant data affixing
`5 means 101, and a receiver 200 comprises deciphering means
`201 for deciphering the enciphered data received via a
`transmission line, appendant data detecting means 202 for
`detecting the appendant data affixed to the input data, and
`cipher key determining means 203 for causing the decipher-
`10 ing means 201 to change a cipher key used for the deci(cid:173)
`phering, in accordance with an error rate of the detected
`appendant data.
`In the transmitter 100, the appendant data, which allows
`the occurrence of an error on the transmission line to be
`detected, is affixed to the input data to be enciphered, and the
`15 appendant data and the input data are enciphered at the
`enciphering means 102. The enciphering means 102 has a
`table including a plurality of cipher keys, and occasionally
`changes the cipher key used for the enciphering as required.
`In the receiver 200, the deciphering means 201 deciphers the
`20 received data, and the appendant data detecting means 202
`detects the appendant data from the deciphered data. The
`cipher key determining means 203 first calculates the error
`rate of the detected appendant data, and if the calculated
`error rate is small, judges that an error has occurred on the
`transmission line. If the error rate is greater than a prede(cid:173)
`termined value, the determining means 203 judges that an
`erroneous cipher key is used by the deciphering means 201,
`and instructs the deciphering means 201 to use a different
`cipher key. Thus, a correct cipher key is always selected and
`30 used at the receiving side.
`FIG. 2 illustrates the configuration of an enciphered
`communication system according to a first embodiment of
`the present invention. As shown in the figure, the enciphered
`35 communication system of the present invention comprises a
`transmitter 100, a receiver 200, and a transmission line 300
`connecting the transmitter and the receiver.
`The transmitter 100 includes an error-detection coding
`section no for receiving input data and affixing an error-
`40 detecting code to the input data. The error-detection coding
`section no corresponds to the appendant data affixing
`means 101 in FIG. 1 illustrating the principles of the
`invention, and for the error-detecting code, an error-detect(cid:173)
`ing/correcting code such as a parity-checking code, a BCH
`(Bose-Chaudhuri-Hocquenghem) code, or a convolutional
`code is used. The transmitter 100 further includes a data
`enciphering section 111 for enciphering the input data by
`means of a cipher key ks, a cipher key table 112 for
`converting a specified number N(ks) to a cipher key ks, a
`so cipher key number setting section 113 for setting a number
`N(ks) by which a cipher key ks in the cipher key table 112
`is selected to be used for enciphering the input data, a cipher
`key number sending section 114 for sending the cipher key
`number N(ks) selected by the cip~er key number setting
`55 section 113 to the receiver 200, and a multiplexing section
`115 for multiplexing the enciphered data and the cipher key
`number N(ks), these elements corresponding to the enci(cid:173)
`phering means 102 in FIG. 1 illustrating the principles of the
`present invention.
`The receiver 200 includes a separating section 210 for
`receiving data transmitted via the transmission line 300 and
`separating the received data into the enciphered data and the
`cipher key number, a cipher key number receiving section
`211 for receiving the separated cipher key number, a cipher
`65 key table 212 having the same contents as the cipher key
`table 112 of the transmitter 100, and a data deciphering
`section 213 for deciphering the separated enciphered data by
`
`45
`
`60
`
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`

`5,574,785
`
`15
`
`25
`
`5
`means of a specified cipher key ks. These elements com:-(cid:173)
`spond to the deciphering means 201 in FIG. 1 illustrating the
`principles of the invention. The receiver 200 further includes
`an error detecting section 214 for detecting the error-detect(cid:173)
`ing code in the data deciphered by the data deciphering 5
`section 213 and for identifying erroneous bit(s), and a cipher
`key determining section 215 for causing the cipher key
`being used for the deciphering to be changed in accordance
`with the number of errors detected within a fixed time by the
`error detecting section 214, i.e., the error rate. The error 10
`detecting section 214 corresponds to the appendant data
`detecting means 202 in FIG. 1, and the cipher key deter-(cid:173)
`mining section 215 corresponds to the cipher key determin(cid:173)
`ing means 203.
`Thus, the transmitter 100 and the receiver 200 are each
`provided with a plurality of cipher keys, a cipher key
`number is allotted to each cipher key, and a collation table
`consisting of the cipher keys and the cipher key numbers
`corresponding thereto is stored in each of the cipher key
`tables 112 and 212. When the cipher key is to be changed,
`the cipher key number setting section 113 of the transmitter
`100 sets a cipher key number N(ks) so that a corresponding
`one of the pre-stored cipher keys ks may be selected. The
`cipher key number N(ks) thus set is converted to a corre(cid:173)
`sponding cipher key ks at the cipher key table 112, and the
`cipher key ks is used at the data enciphering section 111.
`Also, the cipher key number N(ks) is notified to the receiv(cid:173)
`ing side via the cipher key number sending section 114 and
`the multiplexing section 115. The error-detecting code is
`affixed to the input data at the error-detection coding section 30
`110, and the data is enciphered at the data enciphering
`section 111.
`1n the receiver 200, the separating section 210 separates
`the cipher key number from the multiplexed data, and the
`cipher key number thus separated is supplied to the cipher
`key number receiving section 211. The received cipher key
`number may have become erroneous during transmission via
`the transmission line 300, and thus is indicated at N(ks)'.
`Assuming that the received cipher key number N(ks)' equals
`the correct cipher key number N(ks), the cipher key deter- 40
`mining section 215 refers to the cipher key table 212 and
`selects a cipher key ks corresponding to the received cipher
`key number N(ks), and the data deciphering section 213
`deciphers the data by using the selected cipher key ks. Using
`the error-detecting code, the error detecting section 214 45
`determines whether the error-detection coded data deci(cid:173)
`phered by the data deciphering means 213 contains an error.
`If an error is detected, the error detecting section 214 outputs
`error-detection infonnation ERR. On receiving the error
`detection information ERR from the error detecting section 5o
`214, the cipher key determining section 215 determines
`whether the error has occurred accidentally on the transmis(cid:173)
`sion line 300 or has occurred because the cipher key is in
`error. If !he error rate is high and thus it is judged that the
`cipher key is in error, the cipher key number is changed to 55
`a new one and the deciphering is carried out again using a
`cipher key corresponding to the new cipher key number.
`Change of the cipher key number is repeated until no error
`is detected by the error detecting section 214 or the error rate
`becomes smaller than a predetermined error rate.
`FIG. 3 shows an example of the arrangement of the cipher
`key determining section. As illustrated, the cipher key
`determining section 215 comprises an error rate calculating
`section 2151 for receiving the error detection information
`ERR from the error detecting section 214, an error rate 65
`setting section 2152, a determining section 2153, and a key
`number switching section 2154 for receiving and holding the
`
`6
`cipher key number N(ks)' supplied from the cipher key
`number receiving section 211 and supplying the cipher key
`number to the cipher key table 212 as the cipher key number
`N(ks).
`.
`The error rate calculating section 2151 calculates the error
`rate based on the error detection information ERR supplied
`from the error detecting section 214. The determining sec(c