Abstract:
An IP telephone apparatus includes a recording unit, a timestamp token obtaining unit, an operation unit and a data accumulation unit. The recording unit generates recorded data by recording a voice. The timestamp token obtaining unit obtains a timestamp token including encrypted data of the recorded data or digest-data thereof with time information attached. The operation unit initiates the timestamp token obtaining process of the timestamp token obtaining unit. The data accumulation unit accumulates, together with the recorded data, the timestamp token obtained by the timestamp token obtaining unit. By using the IP telephone apparatus, notarized recorded data can be easily obtained and freely handled.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an IP telephone apparatus, an IP telephone system and an IP facsimile apparatus that have a timestamp function for notarizing recording date and time of recorded data.  
         [0003]     2. Description of Related Art  
         [0004]     In recent years, an IP telephone apparatus that communicates voice data with a destination apparatus via an IP network is rapidly gaining popularity, because of the advantages of low rates and multifunctionality. Further, a recording function for recording voice during user&#39;s absence or during a call is normally provided in a telephone apparatus, and the recording function has been frequently used.  
         [0005]     Related to the call recording function, there is a system which, linked to a timestamp server and a time notary center, can issue a timestamp token for notarizing date and time of data recorded during a call and facsimile data (see Related Art 1). In this system, a client obtains a timestamp token for recorded data and facsimile data by using a timestamp-obtaining unit provided in a switch.  
         [0006]     [Related Art 1] Japanese Patent Laid Open Publication 2004-194306.  
         [0007]     However, in the case of a recording function usually provided in a telephone apparatus, time information based on an internal clock is attached to recorded data. Although a user can recognize date and time of recording based on the time information, the time information has no notarizing authority. Therefore, there is a problem that the time when the recording was performed cannot be clearly and strictly certified.  
         [0008]     On the other hand, in the above-mentioned system, in which a timestamp token is created in a switch, time of a call and time of a facsimile communication can be certified with notarizing authority. However, there is a problem that the created timestamp token is kept in the server and cannot be easily obtained and used by a general user according to the user&#39;s needs.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention is provided to resolve the above-described problems associated with the conventional technology. The main purpose of the present invention is to provide a telephone apparatus, a telephone system and a facsimile apparatus, which are so configured that a timestamp token can be easily obtained on the user side and, further, the obtained timestamp token can be freely utilized.  
         [0010]     In order to achieve the above-described objective, as indicated in claim  1 , the telephone apparatus of the present invention, which is connected with another telephone apparatus and a time delivery authority to transmit time information via a network, comprises a memory to store data, a recording unit to record recording data in said memory according to voice data communicated with the another telephone apparatus, a communication unit to transmit a request for the time information to the time delivery authority, a digest data generator to generate digest data based on the recording data recorded in said memory, a time stamp unit to encrypt the digest data and the time information and to generate time stamp token, and a data writing unit to record the time stamp token in said memory.  
         [0011]     According to the present invention, the timestamp token notarizing the date and time of the recorded data can be easily obtained on the user side.  
         [0012]     In this case, for the digest-data, data based on an irreversible transformation, in particular, hash values computed by using a hash function, are among the most suitable. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The present invention is further described in the detailed description which follows, with reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:  
         [0014]      FIG. 1  is a block diagram illustrating an IP telephone apparatus according to a first embodiment of the present invention;  
         [0015]      FIG. 2  is a plain view showing an exterior appearance of the IP telephone apparatus of  FIG. 1 ;  
         [0016]      FIG. 3  shows an example of a list of recorded data sets in the IP telephone apparatus of  FIG. 1 ;  
         [0017]      FIG. 4  is a flow chart describing an operation for generating notarized recorded data in the IP telephone apparatus of  FIG. 1 ;  
         [0018]      FIG. 5  is a flow chart describing a modified example of the operation of the IP telephone apparatus shown in  FIG. 4 ;  
         [0019]      FIG. 6  is a block diagram illustrating an IP telephone apparatus according to a second embodiment of the present invention;  
         [0020]      FIG. 7  is a flow chart describing an operation for generating notarized recorded data in the IP telephone apparatus of  FIG. 6 ;  
         [0021]      FIG. 8  is a flow chart describing a modified example of the operation of IP telephone apparatus shown in  FIG. 7 ;  
         [0022]      FIG. 9  is a block diagram illustrating an IP telephone apparatus according to a third embodiment of the present invention; and  
         [0023]      FIG. 10  is a block diagram illustrating an IP facsimile apparatus according to a fourth embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0024]     The embodiments of the present invention are explained in the following with reference to the above-described drawings.  
       First Embodiment  
       [0025]      FIG. 1  is a block diagram illustrating an IP telephone apparatus according to a first embodiment of the present invention. IP telephone apparatus  1  performs voice communication with IP telephone apparatus (hereafter referred to as “destination apparatus”)  3  via IP network  2  by using a VoIP (voice over internet protocol) technology to convert voice into IP packets. IP telephone apparatus  1  has a timestamp function for notarizing recorded data generated by recording voice in the voice communication. IP telephone apparatus  1  includes chiefly IP communication unit  11 , voice processing unit  12 , recording unit  13 , timestamp obtaining unit  14 , data writing unit  15 , memory card  16 , reader/writer  17 , reproduction unit  18 , verification unit  19 , operation panel  20 , main controller  21 , memory  22 , speaker  23 , microphone  24 , speaker/microphone I/F  25  and operation panel I/F  26 . Besides destination apparatus  3 , IP telephone apparatus  1  is connected via IP network  2  to time-delivery authority (TA)  31 , time stamping authority (TSA)  32  and certification authority (CA)  33 . All of these collectively comprise IP telephone system  40 .  
         [0026]     In IP telephone system  40 , time-delivery authority  31  delivers, to time stamping authority  32 , time information  41  based on a standard time, and authenticates the time of time stamping authority  32 .  
         [0027]     Time stamping authority  32  receives authentication of time from time-delivery authority  31 , and issues a timestamp token (time certificate)  42  in response to a timestamp request from IP telephone apparatus  1 . Timestamp token  42  is issued as an encryption of a combination of hash value  43  sent from a user and time information and the like attached to hash value  43 , by using a private key (that is, it is issued as a digital signature). Timestamp token  42  enables certification that a user&#39;s electronic data (recorded data and the like) corresponding to hash value  43  are in a state as of the time indicated by time information  41  contained in timestamp token  42  (that is, no improper alteration after the time), and that the user&#39;s electronic data existed before the time.  
         [0028]     Certification authority  33  certifies validity of a public key by issuing public key certificate  44 , which correlates the public key to an entity on the network. In the current embodiment, certification authority  33  certifies the issuer of timestamp token  42  by issuing public key certificate  44  for the public key corresponding to the private key used by time stamping authority  32  when issuing timestamp token  42 . This enables a receiver of the public key (verifier of the time) to confirm whether the public key is valid (i.e., whether or not the public key is issued by time stamping authority  32 ) by using public key certificate  44 . Further, it is possible to prevent alteration of the public key certificate itself by adding an electronic signature of certification authority  33  to public key certificate  44 .  
         [0029]     IP communication unit  11  of IP telephone apparatus  1  transmits and receives voice data related to a telephone call to and from destination apparatus  3  via IP network  2  according to a predetermined communication protocol, and also transmits and receives, to and from time stamping authority  32  and certification authority  33 , data related to the timestamp function (a timestamp request, a timestamp token, a public key certificate and the like).  
         [0030]     Voice processing unit  12  has a function for AD and D/A conversions of transmission data and reception data, and a voice CODEC function based on a predetermined encoding method (for example, ITU-T recommendation G.711 and G.729). In other words, voice processing unit  12  creates transmission data by performing an AND conversion for analog signals of a transmission voice and encoding the converted digital data; and, at the same time, voice processing unit  12  generates analog signals of a reception voice by decoding encoded reception data and performing a D/A conversion for the decoded digital data.  
         [0031]     Recording unit  13  records transmission voice transmitted to destination apparatus  3  and reception voice received from destination apparatus  3  (voice of a telephone call). Generated recorded data  51  are saved to memory  22 . Recorded data  51  can be generated in a variety of file formats based on the transmission data and reception data obtained from voice processing unit  12 , and can be suitably compressed as far as voice quality required for reproducing voice can be maintained. Further, the voice, which is to be recorded, is not limited to voice during a telephone call. It may also include sound captured by microphone  24  and reception voice recorded by using an answering machine function, when IP telephone apparatus  1  is not used for a telephone call.  
         [0032]     Timestamp obtaining unit  14  executes a process for obtaining timestamp token  42  from time stamping authority  32 . Hash value computing unit  52  of timestamp obtaining unit  14  obtains recorded data  51 , which require notarization, from memory  22 , computes hash value  43  as digest data of recorded data  51 , and requests a timestamp by transmitting hash value  43  to time stamping authority  32 . The digest data is a fixed length data obtained from original data by using an irreversible one-way function, for example, hash value obtained by using hash function. The same digest data can be obtained from identical data, while there is a very few probability that the same digest data is obtained from different data.  
         [0033]     Data writing unit  15  performs a process for saving recorded data  51 , timestamp token  42  and public key certificate  44  to memory card  16  through reader/writer  17 , recorded data  51  being accumulated in memory  22  and requiring notarization, timestamp token  42  being issued from time stamping authority  32 , and public key certificate  44  being issued from certification authority  33  and containing a public key. When doing so, by creating an information table which correlates among recorded data  51 , timestamp token  42  and public key certificate  44 , it is also possible to save these data separately to different memory devices. Alternatively, it is also possible to put recorded data  51 , timestamp token  42  and public key certificate  44  together and save them as one set of data.  
         [0034]     Memory card (data accumulation unit)  16  is a nonvolatile memory medium, capable of storing a wide variety of data. By using reader/writer  17 , a user can removably attach memory card  16  to IP telephone apparatus  1 . Thereby, recorded data and the like can be saved to memory card  16 , and recorded data and the like already stored in memory card  16  can be read out. The use of memory card  16  makes storing and handling of notarized recorded data easy.  
         [0035]     Reproduction unit  18  performs a process for reproducing recorded data stored in memory card  16  and memory  22  and outputting voice from speaker  23 . Thereby, a user can retrieve required voice data and determine whether notarization is required, by checking the content of the recorded data.  
         [0036]     Verification unit  19  performs a process for verifying time by analyzing recorded data that have already been notarized and the corresponding timestamp token  42 . More specifically, verification unit  19  makes hash value computing unit  52  to compute the hash value of the recorded data, which is to be verified, and compares the resulting hash value with the hash value obtained from the timestamp token, which is to be verified. As a result of the comparison, verification unit  19  determines that the time information of the timestamp token is valid when the two hash values are identical. In this case, the validity of the timestamp token can be determined based on the public key certificate.  
         [0037]     It is also possible for verification unit  19  to perform verification by analyzing recorded data and a corresponding timestamp token obtained through memory card  16 , the recorded data having been already notarized (with a timestamp token attached) by a separate data processing apparatus.  
         [0038]     It is also possible to have a configuration in which IP telephone system  40  includes a data processing apparatus having the same function as verification unit  19 , and the same verification is performed by the data processing apparatus. In this case, memory card  16  storing notarized recorded data is attached to the data processing apparatus so that the recorded data can be read to the data processing apparatus. Thereby, verification and reproduction can be easily performed.  
         [0039]     Operation panel  20  is for use to input settings related to the operation of IP telephone apparatus  1  and to obtain various information. As shown in  FIG. 2 , operation panel  20  includes display  61 , recording button  62 , timestamp button (operation unit)  63 , speaker button  65 , and answering machine button  66 . Display  61  displays various information. Recording button  62  is used to make recording unit  13  to start recording voice. Timestamp button  63  is used to make hash value computing unit  52  to send out a timestamp request. Speaker button  65  is used to switch to a hands-free mode to output voice from speaker  23  without lifting handset  64 . Answering machine button  66  is used to activate the answering machine function. When a user determines that it is necessary to record a telephone call or to record a message and the like when there is no telephone call in progress, the user can start recording by depressing recording button  62 . When a user determines that it is necessary to notarize recorded data  51 , the user can start a process for notarization by depressing timestamp button  63 . Alternatively, it is also possible to have a configuration in which, without the need of depressing recording button  62 , voice of a telephone call is always recorded and saved to memory  22 , and, upon depressing timestamp button  63 , a process for notarizing the recorded data stored in memory  22  is executed.  
         [0040]     As shown in  FIG. 3 , a list of recorded data sets stored in memory  22  or memory card  16  can be displayed on display  61  of operation panel  20 . Relevant information helpful for identifying each recorded data set is displayed. In this example, as relevant information, information for “date,” “time,” “timestamp” and “called party” of a recording are displayed. “Date” shows the date when each recorded data set was recorded. “Time” shows the starting and ending times of each recorded data set. “Timestamp” indicates whether a recorded data set has been notarized, using a circle mark. “Called party” shows a called party&#39;s telephone number “xx-xxxx-xxxx” for data recorded during a telephone call, and “memo” (which indicates a message recording) for data recorded when there was no telephone call in progress.  
         [0041]     Thereby, a user can easily check whether a recorded data set has been notarized already, its attributes and the like, and can easily handle generated recorded data. The relevant information of a recorded data set is not limited to what is described above. A variety of information can be saved beforehand together with recorded data and displayed as needed on display  61 .  
         [0042]     Main controller  21  has an overall control over operations of the above-described units. In particular, with regard to the timestamp function of IP telephone apparatus  1 , main controller  21  controls operations of the above-described recording unit  13 , timestamp obtaining unit  14 , operation panel  20  and the like.  
         [0043]     Although destination apparatus  3  is not required to have a timestamp function as that of IP telephone apparatus  1 , destination apparatus  3 , same as IP telephone apparatus  1 , has a function enabling voice communication by converting voice to IP packets, based on the VoIP technology.  
         [0044]     Next, operations related to the above-described timestamp function of IP telephone apparatus  1  according to the first embodiment will be explained.  
         [0045]      FIG. 4  is a flow chart describing an operation for generating notarized recorded data in the IP telephone apparatus shown in  FIG. 1 .  FIG. 4  describes a case where a notarization process is executed after recording has started, according to an operation by a user during a telephone call.  
         [0046]     First, the user picks up a handset of IP telephone apparatus  1  and starts a telephone call with destination apparatus  3  according to a predetermined connection protocol (for example, the H.323 protocol) (ST 101 ). When the user decides that it is necessary to record the telephone call and depresses recording button  62  (ST  02 ), recording of the telephone call by recording unit  13  starts (ST 103 ). Next, when the user decides that it is necessary to notarize the recorded data and depresses timestamp button  63  (ST 104 ), main controller  21  activates the timestamp function. Thereafter, once the user terminates the telephone call by putting down the handset (ST 105 ), the recording of the telephone call terminates (ST 106 ). The termination of the recording does not always have to be after the termination of the telephone call. For example, it is also possible to have a configuration in which the recording is terminated by depressing the recording button again during the telephone call. Further, the depressing of timestamp button  63  in step ST 104  does not always have to be in the middle of the recording. It is also possible for the user to do the operation when the user decides that it is necessary to notarize the recorded data after the telephone call has ended.  
         [0047]     Once recorded data  51  are generated upon the termination of the recording, based on the activated timestamp function, hash value computing unit  52  computes hash value  43  of recorded data  51  (ST 107 ), and timestamp obtaining unit  14  transmits, to time stamping authority  32 , a timestamp request for hash value  43  (ST 108 ). Time stamping authority  32  receives the timestamp request (ST 201 ). In response to the request, time stamping authority  32  generates timestamp token  42  (ST 202 ) and transmits timestamp token  42  to IP telephone apparatus  1  (ST 203 ).  
         [0048]     Once IP telephone apparatus  1  receives timestamp token  42  from time stamping authority  32  (ST 1  O 9 ), data writing unit  15  obtains recorded data  51 , which are to be notarized, from memory  22 , and saves recorded data  51 , timestamp token  42  and corresponding public key certificate  44  to memory card  16  (ST 110 ). By the series of operations described above, recorded data having date and time of recording notarized are obtained.  
         [0049]     Public key certificate  44  relates to a public key corresponding to a private key of a digital signature when time stamping authority  32  issues timestamp token  42 . Although omitted from the steps described above, after receiving timestamp token  42 , IP telephone apparatus  1  can obtain public key certificate  44  by transmitting a request to certification authority  33 .  
         [0050]      FIG. 5  is a flow chart describing a modified example of the operation of the IP telephone apparatus shown in  FIG. 4 . The operation shown in  FIG. 5  is different from that of  FIG. 4  in that recording of the voice of a telephone call is constantly performed, independent of the recording button. Further, items that are not specifically mentioned are the same as in the case of  FIG. 4 .  
         [0051]     First, when a user starts a telephone call with destination apparatus  3  (ST 301 ), recording of the voice of the telephone call is automatically started by recording unit  13  (ST 302 ). Thereafter, when the user decides that it is necessary to notarize the recorded data and depresses timestamp button  63  (ST 303 ), main controller  21  activates the timestamp function. Thereby, the data being recorded is specified to be notarized, and a notarization process will be executed after recorded data  51  is generated.  
         [0052]     After timestamp button  63  is depressed, the operation of IP telephone apparatus  1  (ST 304 -ST 309 ) and the operation of time stamping authority  32  (ST 401 -ST 403 ) are the same as the operation of IP telephone apparatus  1  (ST 105 -ST 110 ) and the operation of time stamping authority  32  (ST 201 -ST 203 ) shown in  FIG. 4 , respectively.  
         [0053]     According to the above-described configuration, even in a case such as when the user realized in the middle of (or after) a telephone call that notarization is necessary, it is still possible to specify the data recorded from the beginning of the telephone as data to be notarized. Further, it is also possible to have a configuration in which the constantly recorded voice of a telephone call is temporarily accumulated in a separate memory device or the like, and, by depressing the timestamp button, the temporarily accumulated recorded data is saved to memory  22  as data to be notarized. In this case, unneeded recorded data is not accumulated and can be deleted sequentially, thereby enabling an effective use of memory  22 .  
       Second Embodiment  
       [0054]      FIG. 6  is a block diagram illustrating an IP telephone apparatus according to a second embodiment of the present invention. Although IP telephone apparatus  101  has a configuration that is basically the same as IP telephone apparatus  1  shown in  FIG. 1 , it is different from IP telephone apparatus  1  shown in  FIG. 1  in that a timestamp obtaining unit has the same function as time stamping authority  32  shown in  FIG. 1 . In  FIG. 6 , the components that are the same as in IP telephone apparatus  1  of  FIG. 1  are assigned the same numbers, and items that are not specifically mentioned are the same as in the case of IP telephone apparatus  1  of  FIG. 1 . In the present embodiment, time stamping authority  32  shown in  FIG. 1  is no longer required in IP telephone system  140 .  
         [0055]     In timestamp obtaining unit  114  of IP telephone apparatus  101 , hash value computing unit  52  computes hash value  43  as a digest data of recorded data  51 , which requires notarization, and timestamp unit  127  attaches time information and the like to hash value  43  and generates a digital signature using private key  128 . Thereby, timestamp obtaining unit  114  issues timestamp token  142 .  
         [0056]     At this time, time-delivery authority  31  delivers time information  41 , which is based on a standard time, to timestamp unit  127 , and certifies the time of timestamp unit  127 . Certification authority  33  certifies the issuer of timestamp token  142  by issuing public key certificate  144  for a public key corresponding to private key  128 , which is used by timestamp unit  127  when issuing timestamp token  142 . Data writing unit  15  saves recorded data  51 , timestamp token  142  and public key certificate  144  to memory card  16  via reader/writer  17 , recorded data  51  being accumulated in memory  22  and needing notarization, timestamp token  142  being issued by timestamp unit  127 , and public key certificate  144  containing the public key and being issued by certification authority  33 .  
         [0057]      FIG. 7  is a flow chart describing an operation for generating notarized recorded data in the IP telephone apparatus of  FIG. 6 . Similar to the case of  FIG. 4 ,  FIG. 7  describes a case where a notarization process is executed after recording has started, in response to an operation by a user during a telephone call.  
         [0058]     First, the user picks up a handset of IP telephone apparatus  101  and starts a telephone call with destination apparatus  3  according to a predetermined connection protocol (for example, the H.323 protocol) (ST 501 ). When the user depresses recording button  62  (ST 502 ), recording of the telephone call by recording unit  13  starts (ST 503 ). Next, when the user depresses timestamp button  63  during recording (ST 504 ), timestamp unit  127  transmits a time-delivery request to time-delivery authority  31  (ST 505 ). Upon receiving the time-delivery request (ST 601 ), time-delivery authority  31  transmits current time information  41  to IP telephone apparatus  101  in response to the request (ST 602 ). IP telephone apparatus  101  receives time information  41  from time-delivery authority  31  (ST 506 ). Thereafter, when the user puts down the handset and terminates the telephone call (ST 507 ), the recording of the telephone call terminates (ST 508 ). The termination of the recording does not always have to be after the termination of the telephone call. For example, it is also possible to have a configuration in which the recording is terminated by depressing recording button  62  again during the telephone call. Further, the depressing of timestamp button  63  in step ST 504  does not always have to be during the recording. It is also possible for the user to do the operation when the user decides that it is necessary to notarize the recorded data after the telephone call has ended.  
         [0059]     Once recorded data  51  are generated upon the termination of the recording, timestamp obtaining unit  114  computes hash value  43  of recorded data  51  by using hash value computing unit  52  (ST 509 ), and generates timestamp token  142  by attaching time information  41  and the like to hash value  43  and generating a digital signature using private key  128  (ST 510 ). Data writing unit  15  obtains timestamp token  142  generated by timestamp obtaining unit  114 , obtains recorded data  51 , which is to be notarized, from memory  22 , and saves timestamp token  142  and recorded data  51 , together with public key certificate  144 , to memory card  16  (ST 511 ). By the above described series of operations, recorded data having notarized recording time are obtained.  
         [0060]     Public key certificate  144  relates to a public key corresponding to a private key of a digital signature when timestamp unit  127  issues timestamp token  142 . Although omitted from the steps described above, public key certificate  144  can be obtained by transmitting a request to certification authority  33 , when timestamp token  142  is generated.  
         [0061]      FIG. 8  is a flow chart describing a modified example of the operation of the IP telephone apparatus shown in  FIG. 7 . The operation shown in  FIG. 8  is different from that of  FIG. 7  in that the recording of a telephone call is constantly performed during the telephone call, independent of the recording button. Further, items that are not specifically mentioned are the same as in the case of  FIG. 7 .  
         [0062]     First, when a user starts a telephone call with destination apparatus  3  (ST 701 ), recording of the telephone call is automatically started by recording unit  13  (ST 702 ). Thereafter, when the user decides that it is necessary to notarize the recorded data and depresses timestamp button  63  (ST 703 ), main controller  21  activates the timestamp function. Thereby, the data being recorded is specified to be notarized, and a notarization process will be executed after recorded data  51  is generated.  
         [0063]     After timestamp button  63  is depressed, the operation of IP telephone apparatus  101  (ST 704 -ST 709 ) and the operation of time-delivery authority  31  (ST 801 , ST 802 ) are the same as the operation of IP telephone apparatus  101  (ST 505 -ST 511 ) and the operation of time-delivery authority  31  (ST 601 , ST 602 ) shown in  FIG. 7 , respectively.  
       Third Embodiment  
       [0064]      FIG. 9  is a block diagram illustrating an IP telephone apparatus according to a third embodiment of the present invention. Although IP telephone apparatus  201  has a configuration that is basically the same as IP telephone apparatus  1  according to the first embodiment shown in  FIG. 1 , it is different from IP telephone apparatus  1  shown in  FIG. 1  in that relevant information is added to the recorded data, which is to be notarized. In  FIG. 9 , the components that are the same as in IP telephone apparatus  1  of  FIG. 1  are assigned the same numbers, and, for simplicity, only substantial components are shown. Omitted components and items that are not specifically mentioned are the same as in the case of IP telephone apparatus  1  of  FIG. 1 .  
         [0065]     In timestamp obtaining unit  14  of IP telephone apparatus  201 , hash value computing unit  52  computes hash value  43  as a digest data of recorded data  51 , which requires notarization, and main controller  21  obtains relevant information  253  of recorded data  51 . Relevant information  253  includes information about the beginning and ending times of the telephone call, which are obtained from local clock (internal clock)  254  when the telephone call is made, and information about the caller and receiver telephone numbers (information identifying the caller and receiver), which are obtained from IP communication unit  11  when the telephone call is made. Further, hash value computing unit  52  combines computed hash value  43  and obtained relevant information  253 , and transmits the combination to time stamping authority  32 , thereby making a timestamp request. Time stamping authority  32  adds time information  41  to the data combining hash value  43  and relevant information  253 , and issues timestamp token  242 . Data writing unit  15  saves recorded data  51 , timestamp token  242  and public key certificate  44  to memory card  16  via reader/writer  17 , recorded data  51  being accumulated in memory  22  and needing notarization, timestamp token  242  being issued by time stamping authority  32 , and public key certificate  44  containing the public key and being issued by certification authority  33 .  
         [0066]     As an alternative method, it is also possible to have a configuration in which hash value computing unit  52  combines recorded data  51  and relevant information  253 , and computes the hash value of the combined data, and time stamping authority  32  issues a timestamp token for the hash value.  
         [0067]     Further, the above described configuration, in which relevant information is added to the recorded data to be notarized, is similarly applicable to the IP telephone apparatus according to the second embodiment shown in  FIG. 6 . In this case, when the timestamp button is operated, based on the time information (confirmation time) obtained from the time delivery authority in response to the operation, it is possible to obtained a timestamp token having as the object of notarization the recorded data that has been attached the information, related to the beginning and ending times of the telephone call.  
       Fourth Embodiment  
       [0068]      FIG. 10  is a block diagram illustrating an IP facsimile apparatus according to a fourth embodiment of the present invention. Although IP facsimile apparatus  301  has a configuration that is basically the same as IP telephone apparatus  1  according to the first embodiment shown in  FIG. 1 , it is different from IP telephone apparatus  1  in that a facsimile function is added and in that, in addition to recorded data, image data of a facsimile is also notarized. In  FIG. 10 , the components that are the same as in IP telephone apparatus  1  of  FIG. 1  are assigned the same numbers, and items that are not specifically mentioned are the same as in the case of IP telephone apparatus  1  of  FIG. 1 .  
         [0069]     In addition to the configuration of IP telephone apparatus  1  shown in  FIG. 1 , IP facsimile apparatus  301  further has document reading unit  334 , image processing unit  335 , image formation unit  336  and voice recognition unit  337 . Document reading unit  334  scans documents and generates image data for facsimile communication. Image processing unit  335  has A/D and D/A conversion functions and performs predetermined image processing, such as image composition, reduction and rotation, to the image data. Image formation unit  336  produces images on predetermined papers, based on the processed image data. Voice recognition unit  337  generates text data by executing a voice recognition process on recorded data  51 .  
         [0070]     In IP facsimile apparatus  301 , notarization process of recorded data  51  can be executed the same way as in the case of IP telephone apparatus  1  of  FIG. 1 . Notarization process of image data  340  is executed as follows.  
         [0071]     First, image data received from a facsimile apparatus, are processed by image processing unit  335 , and then accumulated in memory  22  as image data  340 , which is to be notarized. In timestamp obtaining unit  14 , hash value computing unit  52  obtains image data  340  that needs notarization, computes hash value  343  as a digest data of image data  340 , and performs a timestamp request by transmitting hash value  343  to time stamping authority  32 . Time stamping authority  32  adds time information to hash value  343  and issues timestamp token  342 . Data writing unit  15  saves image data  340 , timestamp token  342  and public key certificate  44  to memory card  16  via reader/writer  17 , image data  340  being accumulated in memory  22  and needing notarization, timestamp token  142  being issued by time stamping authority  32 , and public key certificate  44  containing a public key and being issued by certification authority  33 . Thereby, image data having notarized recording date and time are obtained.  
         [0072]     Image data  340  to be notarized is not limited to image data received from a facsimile apparatus, as described above. For example, image data  340  can also be image data generated by document reading unit  334  through scanning, or text data obtained by voice recognition unit  337  through performing a voice recognition process on recorded data  51 . It is also possible to have a configuration in which image data  340  and recorded data  51  are combined together for notarization, and a timestamp token is issued by time stamping authority  32  for the hash value of the combined data.  
         [0073]     It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to exemplary embodiments, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular structures, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.  
         [0074]     The present invention is not limited to the above described embodiments, and various variations and modifications may be possible without departing from the scope of the present invention.  
         [0075]     This application is based on the Japanese Patent Application No. 2005-263573 filed on Sep. 12, 2005 entire content of which is expressly incorporated by reference herein.