Patent Publication Number: US-9432194-B2

Title: Recording medium with authentication and encryption/decryption functions

Description:
RELATED APPLICATIONS 
     This application claim the benefit of Japanese Application No. 2013-052848, filed on Mar. 15, 2013 and Japanese Application No. 2013-259755, filed Dec. 17, 2013, the disclosures of which Applications are incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present technique relates to a recording medium having a security function and used in a photographing apparatus, for example. 
     2. Description of the Related Art 
     Conventionally, such a recording medium has been realized that can encrypt and store image data captured by a photographing apparatus. To realize encryption, an encryption key is required to encrypt plane text data. Also, a decryption key is required to decode the encrypted data. In some encryption systems, the same key is used as both the encryption key and the decryption key. One or both of the encryption key and the decryption key must be managed securely so as not to be leaked to a third party. 
     As means for securely keeping these key data, such an IC card is considered potent that is designed to make it difficult to decode the stored data on software and on hardware. For example, Unexamined Japanese Patent Publication No. 2001-320668 discloses a photographing apparatus which stores key data confidentially in a storage device such as an IC card, and encrypts digital data with the stored key. 
     Further, such a recording medium having a security function is known that makes it possible, when an authentication procedure has not been completed, to select either a mode in which the captured image data are not encrypted and stored or a mode in which the captured image data are encrypted and stored. 
     On the other hand, in the business-use photographing apparatus used for news reporting or the like, such an instantaneous operation is required that can start shooting immediately after power-on. However, the recording medium having a security function cannot execute the encryption-recording operation, nor confirm the recorded encrypted contents data, before completing authentication. Therefore, it was difficult for the recording medium having a security function used in the business-use photographing apparatus to balance the instantaneous operation to allow quick start of shooting after power-on with the operation to secure the confidentiality of the recorded data. 
     SUMMARY OF THE INVENTION 
     A recording medium according to the present technique is attachable to and detachable from an apparatus body, and is supplied with power from the apparatus body when it is attached to the apparatus body. This recording medium includes: an encryption/decryption control unit that performs encryption and decryption of data transmitted from the apparatus body; an authentication control unit that performs an authentication procedure for authentication a password sent from the apparatus body; a non-volatile memory that stores an encryption key to be used in the encryption/decryption control unit and the authentication password to be used for authentication in the authentication control unit, and has a data recording area for recording data encrypted by the encryption/decryption control unit; and a volatile memory for storing recorded-position information of data recorded in the data recording area of the non-volatile memory under an unauthenticated condition in which the authentication procedure by the authentication control unit has not been performed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram showing a schematic configuration of a photographing apparatus using a recording medium according to the present technique; 
         FIG. 2  is a block diagram showing a schematic configuration of a recording medium according to an embodiment of the present technique; 
         FIG. 3  is a flowchart showing an operation flow in a case that the recording medium according to the present technique receives an authentication password setting command during a write operation; 
         FIG. 4  is a flowchart showing an operation flow in a case that the recording medium according to the present technique does not receive an authentication password setting command during a write operation; and 
         FIG. 5  is a flowchart showing an operation flow during a read operation of the recording medium according to the present technique. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A recording medium having a security function according to an embodiment of the present technique will hereinafter be described with reference to the drawings. However, unnecessarily detailed description may occasionally be omitted. For example, detailed description of well-known matters and redundant description of substantially the same configurations may occasionally be omitted. This is to avoid the following description from becoming unnecessarily redundant, and to ease understanding of those skilled in the art. 
     Incidentally, the inventor intends to provide the following description and the accompanying drawings to allow any person skilled in the art to fully understand the present technique, and does not intend to limit the subject matter defined in the claims by the following description. 
     The recording medium according to the present technique is used in a photographing apparatus. A schematic configuration of a business-use photographing apparatus will hereinafter be described. 
       FIG. 1  is a block diagram showing a schematic configuration of a photographing apparatus using a recording medium according to the present technique. 
     As shown in  FIG. 1 , apparatus body  10  of a photographing apparatus has: signal input/output unit  11  for inputting and outputting a video signal and an audio signal; signal processing unit  12  that performs signal processing including analog to digital conversion of the video signal and the audio signal and conversion of the video and audio signals to signals in specified signal formats; storage unit  13  such as a flash memory; monitor  14  such as a liquid crystal display; wireless communication unit  15  that performs wireless data transmission to and reception from external equipment; interface unit  16  that performs data transmission and reception between apparatus body  10  and recording medium  20 ; and control unit  17  that controls each of these components. The components in apparatus body  10  perform data transmission and reception via bus  18 . 
     Further, apparatus body  10  is provided with an adapter (not shown in the figure) with which a user can arbitrarily attach and detach recording medium  20 . The adapter is connected to interface unit  16 . Recording medium  20  is supplied with power by being attached to the adapter of apparatus body  10 . This allows recording medium  20  to execute an encryption-recording of data produced by apparatus body  10  and an operation to decode and read out the encryption-recorded data. 
     Signal input/output unit  11  has functions of inputting a video signal and an audio signal from an imaging device, a microphone or the like and outputting a signal processed by signal processing unit  12  to an external monitor, speaker or the like. Signal input/output unit  11  may be configured as communication means that exchange a video signal and an audio signal with external equipment via a communication path. 
     Signal processing unit  12  has signal conversion units such as an encoder and a decoder, and also a buffer for temporarily storing data. 
     Storage unit  13  is provided for storing various setup information of apparatus body  10 . Control unit  17  stores various setup information set by a user in storage unit  13  via bus  18 . The setup information includes information whether or not contents should be encrypted and recorded. 
     Wireless communication unit  15  is an interface module for connecting the apparatus to the internet, and is configured by a wireless LAN module or the like. Wireless communication unit  15  is responsive to an instruction from control unit  17  to communicate with a management server managing authentication passwords, and inquire an authentication password based on a serial number of recording medium  20 . If an authentication password corresponding to the serial number of recording medium  20  is obtained from the management server, the authentication password is stored in a memory of control unit  17 . 
     Control unit  17  has a general arithmetic processor, a memory, a storage area storing programs for operating the arithmetic processor, and the like. Further, control unit  17  has onboard a file system for recording desired data in recording medium  20  as files. 
     The video signal and the audio signal inputted from signal input/output unit  11  are processed in signal processing unit  12  to be converted to encoded digital data. These digital data are stored in the buffer, and then recorded by control unit  17  as data files in recording medium  20  via interface unit  16 . At this time, control unit  17  produces data of a first frame of the encoded digital data as thumbnail images, which are image files in a bitmap format, and records the data in recording medium  20 . The thumbnail images can be displayed as a list of thumbnails on monitor  14  by a user operation. The thumbnail image data are prepared so that, for example, a desired image data can be easily found from recording medium  20 . Accordingly, each image data is compressed to an image data of, for example, vertical 80 pixels by horizontal 60 pixels with each pixel being composed of 24 bits. 
     Further, control unit  17  produces clip management information used for managing and connecting such information as the frame rate, the number of frames, and the duration representing the data size by the number of frames, of the video signal and the audio signal, and produces XML format data files. The clip management information is also recorded in recording medium  20  by the file system. 
       FIG. 2  is a block diagram showing a schematic configuration of a recording medium according to an embodiment of the present technique. 
     As shown in  FIG. 2 , recording medium  20  has operation unit  21 , control unit  22 , storage unit  23  composed of a ROM (Read Only Memory) as a non-volatile memory, volatile memory  24  composed of a RAM (Random Access Memory), non-volatile memory  25  composed of a flash memory, bus  26  for transmitting data between apparatus body  10  and control unit  22 , and bus  27  connecting operation unit  21 , control unit  22 , storage unit  23 , volatile memory  24  and non-volatile memory  25  to allow data transmission among them. With this configuration, operation unit  21  is accessibly connected to control unit  22  containing register group  22   a , storage unit  23 , volatile memory  24  and non-volatile memory  25  via bus  27 . Further, once recording medium  20  is detached from apparatus body  10  and thus power supply is cut, data stored in volatile memory  24  are erased. However, data stored in storage unit  23  and non-volatile memory  25  are kept without being erased even after power supply is cut. 
     Operation unit  21  is connected to bus  27 , and executes control program  23   a  stored as a firmware in storage unit  23  to perform control of control unit  22 . Control program  23   a  stored in storage unit  23  includes therein encryption/decryption control unit  23   b  performing encryption and decryption of data transmitted from apparatus body  10 , and authentication control unit  23   c  performing an authentication procedure for authenticating a password sent from apparatus body  10 . 
     Control unit  22  has register group  22   a , and receives a control command sent from apparatus body  10  via bus  26 . Control unit  22  analyzes the received control command, and stores a command number, a command argument and the like in register group  22   a . Operation unit  21  refers to the values stored in register group  22   a , and executes control program  23   a.    
     Volatile memory  24  is connected to bus  27 , and functions as a work memory of operation unit  21 , while storing various data necessary for the processes performed in recording medium  20 . Volatile memory  24  also contains recorded-position information  24   a  for holding recorded position of data which have been encrypted and recorded under an unauthenticated condition. Here, the unauthenticated condition means a condition in which authentication control unit  23   c  does not perform any authentication procedure for authenticating a password. Further, when recording medium  20  is detached from apparatus body  10  and power supply is cut, data stored in volatile memory  24  are erased. 
     Non-volatile memory  25  is connected to bus  27 , and has an area storing encryption key  25   a  to be used by encryption/decryption control unit  23   b  and authentication password  25   b  to be used for authentication by authentication control unit  23   c , and data recording area  25   c  for recording data encrypted by encryption/decryption control unit  23   b.    
     Encryption key  25   a  is produced at random by encryption/decryption control unit  23   b  when authentication password  25   b  is set by a control command sent from apparatus body  10 . Encryption key  25   a  is used, when a write command is received from apparatus body  10 , by encryption/decryption control unit  23   b  to encrypt data set in a specified address of register group  22   a  from apparatus body  10 . Also, encryption key  25   a  is used, when a read command is received from apparatus body  10 , as a decryption key by encryption/decryption control unit  23   b  to decrypt data read from data recording area  25   c.    
     Authentication password  25   b  is set by an authentication password setting command sent from apparatus body  10 . Authentication password  25   b  is used as a password for authentication by authentication control unit  23   c  when the authentication password setting command is received from apparatus body  10 . 
     Authentication control unit  23   c , when it has received the authentication password setting command from apparatus body  10 , compares a password received as an argument of the authentication password setting command with authentication password  25   b , and, in the case of coincidence, records a success of authentication in volatile memory  24 . Specifically, authentication control unit  23   c  compares the received authentication password with authentication password  25   b  stored in non-volatile memory  25  to check whether or not they coincide with each other. If the received authentication password coincides with the stored authentication password  25   b , or authentication succeeds, authentication control unit  23   c  writes an authentication flag “1” indicating an authenticated state into volatile memory  24 . 
     On the other hand, if authentication does not succeed for the reason that any authentication password is not received from apparatus body  10 , or authentication does not succeed for the reason that the received authentication password does not coincide with the stored authentication password  25   b , authentication control unit  23   c  writes an authentication flag “0” indicating an unauthenticated state into volatile memory  24 . In this way, the authentication flag indicating either the authenticated state or the unauthenticated state is stored in volatile memory  24  as a result of the authentication procedure by authentication control unit  23   c . The authentication flag information indicating the authenticated or unauthenticated state in volatile memory  24  is set to be the unauthenticated state as an initial value at the power up time of recording medium  20 , or the time when recording medium  20  is attached to apparatus body  10 . 
     Data recording area  25   c  is an area for storing data from apparatus body  10  and reading out the stored data. When a write command is received from apparatus body  10 , data set in a specified address of register group  22   a  from apparatus body  10  are recorded in data recording area  25   c  by control program  23   a . At this time, when the write command is received from apparatus body  10 , the data set in the specified address of register group  22   a  from apparatus body  10  are encrypted by encryption/decryption control unit  23   b , and then recorded in data recording area  25   c . Incidentally, in the case of the unauthenticated state, when the write command is received from apparatus body  10 , and data are encrypted by encryption/decryption control unit  23   b  and recorded in data recording area  25   c , recorded-position information  24   a  indicating the recorded position of the data is written into volatile memory  24 . Information used as this recorded-position information  24   a  is file system management information of non-volatile memory  25 . 
     Further, when a read command is received from apparatus body  10 , data read from data recording area  25   c  are recorded in a specified address of register group  22   a  by control program  23   a . At this time, when the read command is received from apparatus body  10 , the data read from data recording area  25   c  are decrypted by encryption/decryption control unit  23   b , and then recorded in register group  22   a . Incidentally, in the case of the unauthenticated state, when the read command is received from apparatus body  10 , recorded-position information  24   a  of non-volatile memory  24  is referred to, and data are read from the position in data recording area  25   c  contained in recorded-position information  24   a.    
     Although encryption/decryption control unit  23   b  and authentication control unit  23   c  are realized by software in the present embodiment described above, they may be realized by hardware by preparing dedicated circuits. 
     Next, an operation of writing data transmitted from apparatus body  10  into a recording medium according to the present technique will be described. 
       FIG. 3  is a flowchart showing an operation flow in a case that the recording medium according to the present technique receives an authentication password setting command during a write operation. 
     First, by inputting an authentication password from apparatus body  10 , recording medium  20  receives an authentication password setting command at step S 301 . 
     Next, authentication control unit  23   c  compares the received authentication password with authentication password  25   b  stored in non-volatile memory  25  to check whether or not they coincide with each other at step S 302 . If the received authentication password coincides with the stored authentication password  25   b , or authentication succeeds, authentication control unit  23   c  writes the authentication flag “1” indicating the authenticated state into volatile memory  24  at step S 303 . Incidentally, the authentication flag information indicating the authenticated or unauthenticated state in volatile memory  24  is set the unauthenticated state as an initial value at the power up time of recording medium  20 , or the time when recording medium  20  is attached to apparatus body  10 . 
     When the information stored in volatile memory  24  indicates the authenticated state, the write data sent from apparatus body  10  are encrypted at step S 304 . The operation of encrypting the write data is performed by encryption/decryption control unit  23   b , which encrypts data set in a specified address of register group  22   a  from apparatus body  10  by using encryption key  25   a  when an encryption-recording command is received from apparatus body  10 . Then, the write data having been encrypted are recorded in data recording area  25   c  of non-volatile memory  25  at step S 305 . 
     After completing recording of the write data in data recording area  25   c  of non-volatile memory  25  at step S 306 , if recording medium  20  is detached from apparatus body  10  at step S 307 , the authentication flag indicating the authenticated state stored in volatile memory  24  is initialized at step S 308 . This ends the write operation in the case that an authentication password setting command is received and authentication succeeds. 
     On the other hand, in a case that the received authentication password does not coincide with the stored authentication password  25   b , or authentication is unsuccessful, at step S 302 , the authentication flag “0” is written into volatile memory  24  at step S 309 . Also, recorded-position information  24   a  of the unauthenticated write data is written into volatile memory  24  at step S 310 . 
     In the following steps, similarly to the authenticated case, the write data sent from apparatus body  10  are encrypted at step S 304 , and the encrypted write data are recorded in data recording area  25   c  of non-volatile memory  25  at step S 305 . When recording of the write data in data recording area  25   c  of non-volatile memory  25  is completed at step S 306 , and recording medium  20  is detached from apparatus body  10  at step S 307 , the authentication flag stored in volatile memory  24  is initialized at step S 308 , and data of recorded-position information  24   a  of the unauthenticated write data is also erased. This ends the write operation in the case that an authentication password setting command is received and authentication does not succeed. 
     In the write operation when an authentication password setting command is received, as described above, the write data are recorded regardless of whether authentication succeeds or not. However, in the case that authentication did not succeed, recorded-position information  24   a  of the write data is erased by detaching recording medium  20  from apparatus body  10 , and consequently it becomes difficult to read out the write data recorded in data recording area  25   c  of non-volatile memory  25 . 
       FIG. 4  is a flowchart showing an operation flow in a case that an authentication password setting command is not received during a write operation. 
     In this case, in which no authentication password is inputted from apparatus body  10 , it is determined at step S 401  whether the authentication flag stored in volatile memory  24  is the authentication flag “1” indicating the authenticated state or the authentication flag “0”. 
     If the information stored in volatile memory  24  is the one indicating the authenticated state, the write data sent from apparatus body  10  are encrypted at step S 402 . The operation of encrypting the write data is performed by encryption/decryption control unit  23   b , which encrypts data set in a specified address of register group  22   a  from apparatus body  10  by using encryption key  25   a  when an encryption-recording command is received from apparatus body  10 . Then, the write data having been encrypted are recorded in data recording area  25   c  of non-volatile memory  25  at step S 403 . 
     After completing recording of the write data in data recording area  25   c  of non-volatile memory  25  at step S 404 , if recording medium  20  is detached from apparatus body  10  at step S 405 , the authentication flag indicating the authenticated state stored in volatile memory  24  is initialized at step S 406 . This ends the write operation in the case that an authentication password setting command is not received and the information stored in volatile memory  24  is the authentication flag “1”. 
     On the other hand, if the information stored in volatile memory  24  is the authentication flag “0” at step S 401 , recorded-position information  24   a  of the unauthenticated write data is written into volatile memory  24  at step S 407 . 
     In the following steps, similarly to the case of the authenticated state, the write data sent from apparatus body  10  are encrypted at step S 402 , and the encrypted write data are recorded in data recording area  25   c  of non-volatile memory  25  at step S 403 . When recording of the write data in data recording area  25   c  of non-volatile memory  25  is completed at step S 404  and recording medium  20  is detached from apparatus body  10  at step S 405 , the authentication flag stored in volatile memory  24  is initialized at step S 406 , and data of recorded-position information  24   a  of the unauthenticated write data is also erased. This ends the write operation in the case of the unauthenticated state. 
     In the write operation when the authentication password setting command is not received, as described above, the write data are recorded regardless of whether recording medium  20  is in the authenticated state or the unauthenticated state. However, in the case of the unauthenticated state, since recorded-position information  24   a  of the write data is erased by detaching recording medium  20  from apparatus body  10 , it becomes difficult to read out the write data recorded in data recording area  25   c  of non-volatile memory  25 . 
     Next, an operation of reading out data recorded in a recording medium according to the present technique will be described. 
       FIG. 5  is a flowchart showing an operation flow during a read operation. 
     When a read command is inputted from apparatus body  10 , control program  23   a  first refers to the status of volatile memory  24 . In other words, it is determined whether the authentication flag stored in volatile memory  24  is the authentication flag “1” indicating the authenticated state or the authentication flag “0” at step S 501 . 
     In the case that the information stored in volatile memory  24  is the one indicating the authenticated state, in which data read-out is possible, data are read out from data recording area  25   c  of non-volatile memory  25  at step S 502 , and the read-out data are decrypted at step S 503  to complete the data read operation at step S 504 . Decryption of data is executed at step S 503  by encryption/decryption control unit  23   b  of storage unit  23  by using encryption key  25   a  as a decryption key. The decrypted data are recorded in a specified address of register group  22   a  by control program  23   a  to be in a state transmissible to apparatus body  10 . 
     In the case that the information stored in volatile memory  24  is the authentication flag “0”, or in the unauthenticated case, the process proceeds to step S 505  to confirm whether recorded-position information  24   a  exists in volatile memory  24  or not. If recorded-position information  24   a  exists at step S 505 , an operation of reading out recorded-position information  24   a  is executed at next step S 506 . In the following steps, similarly to the case of the authenticated state, operations of reading out data from data recording area  25   c  of non-volatile memory  25  based on recorded-position information  24   a  at step S 502  and decrypting the read-out data at step S 503  are performed to complete the data read operation at step S 504 . If recorded-position information  24   a  does not exist at step S 505 , the process ends as an error. 
     Here, the confirmation whether recorded-position information  24   a  exists or not is made by control program  23   a  by referring to, in recorded-position information  24   a , a value of a bit corresponding to a sector of a read address set as an argument of a read command from apparatus body  10 . If the corresponding bit is “1”, it is determined that the recorded-position information exists, and the process proceeds to step S 506 . If the corresponding bit is “0”, it is determined that the recorded-position information does not exist. In this case, a register for notifying an error is set in register group  22   a  to notify the error to apparatus body  10 , and the process ends. 
     Further, even in the case that the information stored in volatile memory  24  is the authentication flag “0”, since it is possible to read out data which were written in a write operation under such a condition that an authentication password setting command had been received and authentication had succeeded, the process proceeds to step S 507  to check the authentication password. 
     In step S 507 , an authentication password is received from apparatus body  10  in the same manner as in the write operation. Then, it is determined whether the input authentication password coincides with authentication password  25   b  stored in non-volatile memory  25  at step S 508 . If the input authentication password coincides with authentication password  25   b , operations of reading out data at step S 502  and decrypting the read-out data at step S 503  are performed, in the same way as in the case of the authenticated state, to complete the data read operation at step S 504 . If the input authentication password does not coincide with authentication password  25   b , the process ends without performing the data read operation. 
     In the read operation, as described above, even in the case that the authentication flag stored in volatile memory  24  is checked whether it indicates the authenticated state or not and determined to be the unauthenticated state, it is possible to read out data written in data recording area  25   c  of non-volatile memory  25  if recorded-position information  24   a  exists in volatile memory  24 . Even in the unauthenticated state, it is of course possible, if the input authentication password coincides with authentication password  25   b , to read out data written in the write operation under condition of successful authentication. 
     As described above, a recording medium according to the present technique has non-volatile memory  25  for recording encrypted data, and volatile memory  24  for storing an authentication flag indicating whether an authentication by an authentication password has been completed or not, and recorded-position information  24   a  of data recorded in non-volatile memory  25  when the authentication flag indicates an unauthenticated state. With this configuration, even in the case that any authentication password has not been obtained, it is possible to encrypt and record data in non-volatile memory  25  by storing recorded-position information  24   a  in volatile memory  24 , as well as to decrypt and read out the encrypted data by referring to recorded-position information  24   a  in volatile memory  24 . Accordingly, if recording medium  20  is in the condition kept attached to apparatus body  10 , it is possible without the password authentication to perform the operation of writing data transmitted from apparatus body  10  and the operation of reading out the written data. 
     Further, by detaching recording medium  20  from apparatus body  10 , the authentication flag stored in volatile memory  24  is initialized, and recorded-position information  24   a  is also erased. Therefore, since an operation of reading out data recorded in non-volatile memory  25  of recording medium  20  cannot be performed under the condition that no authentication password is obtained, it is possible to let recording medium  20  have a security function based on an authentication password. 
     A recording medium used in a business-use photographing apparatus, which is used for news reporting or the like, is required to provide both an instantaneous operation enabling quick start of shooting after power-on and an operation securing confidentiality of recorded data. A recording medium according to the present technique is able to perform an operation of immediately writing shot data and an operation of reading out the written data at the stage when it is attached to apparatus body  10 , or power supply is started, and thus has an instantaneous operation capability. In addition, since it is made impossible to read out data which have been recorded without an authentication based on an authentication password by stopping supply of power by detaching the recording medium from apparatus body  10 , it is possible to secure confidentiality of the recorded information. 
     In the above, an embodiment has been described as an example of the technique according to the present disclosure. The detailed description and accompanying drawings have been provided for that purpose. Accordingly, components shown in the accompanying drawings and described in the detailed description include not only components which are essential to solve the problems, but also components which are not essential to solve the problems, but are used for exemplifying the above-mentioned technique. Therefore, those non-essential components should not be immediately construed as essential for the reason that the non-essential components are shown in the accompanying drawings or described in the detailed description. 
     Also, since the above-described embodiment is to exemplify the technique according to the present disclosure, various modifications, substitutions, additions or omissions may be possible within the scope of the claims or equivalents thereof.