embodiments of the invention will now be described with reference to the attached drawings . referring to fig1 , the first embodiment is a printing medium 1 to which a small ic chip 2 is attached . the ic chip 2 is fastened to the printing medium 1 by an adhesive and is sealed by a heat - resistant seal 3 . the ic chip 2 , is surrounded by a loop antenna 4 . in fig1 , the ic chip 2 is attached near the front right corner of the printing medium 1 with respect to the direction in which the printing medium 1 is transported during printing , but the ic chip 2 may be attached anywhere , on either side of the printing medium 1 , as long as it is located near the front of the printing medium 1 with respect to the printing transport direction . the ic chip 2 may be fastened to the printing medium 1 by any means that prevent removal from the printing medium 1 ; for example , the ic chip 2 may be inserted into the printing medium 1 . referring to fig2 , the ic chip 2 attached to the printing medium 1 comprises an antenna unit 5 , an input - output controller 6 , an access controller 7 , a comparison unit 8 , a first memory 9 , and a second memory 10 . the ic chip 2 uses a contactless communication system in which data are transmitted and received from the antenna unit 5 via the loop antenna 4 shown in fig1 . the antenna unit 5 also supplies power received via the loop antenna 4 to the ic chip 2 . the input - output controller 6 controls the input and output of data received and transmitted from the antenna unit 5 . the access controller 7 controls access to the data stored in the ic chip 2 . the comparison unit 8 decides whether access to the data stored in the ic chip 2 is authorized or not . the first memory 9 and second memory 10 are both nonvolatile memories . authentication data used in decision making by the comparison unit 8 are prestored in the first memory 9 ; validation data transmitted and received as described above are stored in the second memory 10 . fig3 illustrates an image forming apparatus 11 used in the first embodiment of the invention . the image forming apparatus 11 is connected to an external device 12 such as a personal computer or other information processing apparatus . the image forming apparatus 11 prints an image on the printing medium 1 , and can also access the ic chip 2 to read and write data . as shown in fig3 , the image forming apparatus 11 comprises an input - output unit 13 , a controller 14 , an operation panel 15 , a communication unit 16 , and an image forming unit 17 . the input - output unit 13 is an interface circuit that exchanges data with the external device 12 . the input - output unit 13 may be , for example , a usb ( universal serial bus ) interface circuit , a lan ( local area network ) interface circuit , or an rs - 232c ( electronic industries association recommended standard no . 232 version c ) interface circuit . the controller 14 receives data from the input - output unit 13 and converts the received data into various forms , as well as controlling the entire image forming apparatus 11 . the controller 14 includes a memory storing various embedded programs , a processor for executing these programs , and a work memory . the operation panel 15 displays the status of the image forming apparatus 11 according to information received from the controller 14 , and has buttons , keys , or other manual controls for input of various types of information , which is sent to the controller 14 . the communication unit 16 exchanges data with the printing medium 1 . referring to fig4 , the communication unit 16 ( not visible ) in the image forming apparatus 11 can communicate with the printing medium 1 when the printing medium 1 is in a communication region 18 . the conditions satisfied by the communication region 18 include , for example , enabling electromagnetic waves transmitted from the communication unit 16 to reach the printing medium 1 with a certain electric power , and not permitting the electromagnetic waves to reach any other printing media which are stacked or stored in preparation for printing . the image forming unit 17 prints an image on a surface of the printing medium 1 as it is transported through the image forming apparatus 11 . the printing medium 1 incorporating the ic chip 2 may be used for various purposes . to address the problems of the prior art described above , the following descriptions will assume that the printing medium 1 is used for printing a negotiable security . to make the printing medium 1 into a negotiable security incorporating the ic chip 2 , two processes must be performed : first , the title and other information of the security must be printed on the printing medium 1 , and second , information that can certify the validity of the printing medium 1 when it is used as a negotiable security must be stored in the second memory 10 of the ic chip 2 . the validity of the negotiable security is verified by comparing the information printed on the printing medium 1 with the information ( validation data ) stored in the second memory 10 . the validation data are stored in the second memory 10 when an image is printed on the printing medium 1 , to certify the validity of the image printed on the printing medium 1 . in this first embodiment , it is assumed that the information printed on the printing medium 1 includes at least the price of the negotiable security , and that the price data are used as the validation data . in practice , the validation data may be any data that can be compared with the image printed on the printing medium 1 for verification purposes . instead of price data , the validation data may be , for example , issuer data , owner data , or issue date data , or an encrypted form of any of these data . to write the validation data when the external device 12 requests printing of the negotiable security by sending data to be printed , the comparison unit 8 first decides whether to permit write access to the second memory 10 . if write access is permissible , the input - output controller 6 transfers the validation data received via the antenna unit 5 to the access controller 7 , which writes the transferred validation data into the second memory 10 . if write access is not permissible , the receiving and writing of the validation data are not carried out . to read the validation data when the external device 12 requests reading of data to verify the authenticity of the negotiable security , the comparison unit 8 first decides whether to permit read access to the second memory 10 . if read access is permissible , the access controller 7 reads the validation data from the second memory 10 and transfers the validation data to the input - output controller 6 , which transmits the transferred data via the antenna unit 5 . if read access is not permissible , the reading and transmitting of the validation data are not carried out . the authentication data prestored in the first memory 9 are used to decide whether to permit these read and write accesses . the authentication data are prestored in the first memory 9 before the ic chip 2 is attached to the printing medium 1 , and used to authorize access to the ic chip 2 . the authentication data may be any data associated with the printing medium 1 , such as data identifying the manufacturer of the ic chip 2 , data identifying the security issuer who performs printing on the printing medium 1 , data identifying the media type of the printing medium 1 , or serial number data . in this first embodiment , data identifying the media type of the printing medium 1 ( media data ) are employed as authentication data . the image forming apparatus 11 is thus equipped both to print a negotiable security on the printing medium 1 and to read and write the security price data in the second memory 10 . printing is carried out according to printing data sent from the external device 12 to the input - output unit 13 . the controller 14 receives the printing data from the input - output unit 13 , and converts the received printing data into image data to be printed on the printing medium 1 and security price data to be stored in the second memory 10 , while transporting or pre - feeding the printing medium 1 to a predetermined location in the communication region 18 . subsequently , the controller 14 causes the operation panel 15 to display a prompt for input of comparison data . after the operator of the image forming apparatus 11 enters the comparison data on the operation panel 15 , the controller 14 sends the comparison data to the printing medium 1 via the communication unit 16 to confirm the possibility of write access to the second memory 10 . after sending the comparison data , the controller 14 receives a comparison result from the printing medium 1 via the communication unit 16 . if the comparison result indicates that data can be written in the printing medium 1 , the image forming unit 17 performs printing on the printing medium 1 while the communication unit 16 sends the security price data to the ic chip 2 attached to the printing medium 1 . if data cannot be written , printing is canceled and the printing medium 1 is fed back from the communication region 18 into the tray shown at the bottom of fig4 . alternatively , the printing medium 1 may be fed through the image forming apparatus 11 and ejected with no printing performed , so that the surface of the printing medium 1 remains blank . the conversion of the printing data to image data may also be delayed until the comparison result has been received , and performed only if the comparison result indicates that the writing of data is possible . when the security price data stored in the second memory 10 are read , a read request sent by the external device 12 initiates processing by the controller 14 , in which the comparison data entered on the operation panel 15 is sent to the printing medium 1 to confirm whether read access to the printing medium 1 is permissible or not . if read access is permissible , the security price data received from the printing medium 1 are displayed on the operation panel 15 . if read access is not permissible , an error message is displayed on the operation panel 15 . alternatively , the price data and / or error message may be displayed on the external device 12 instead of the operation panel 15 . the flowcharts in fig5 a and 5b illustrate the image printing and data writing operations in the first embodiment . fig5 a shows operations performed by the image forming apparatus 11 ; fig5 b shows operations performed by the ic chip 2 . the printing and writing operations will be described below with reference to these flowcharts . first , the controller 14 in the image forming apparatus 11 receives printing data from the external device 12 via the input - output unit 13 ( step 101 in fig5 a ). while pre - feeding the printing medium 1 , the controller 14 converts the received printing data by executing an embedded program to generate image data to be printed on the printing medium 1 and price data to be sent to the printing medium 1 ( step 102 ). after completion of the above data conversion , the controller 14 requests the entry on the operation panel 15 of comparison data necessary for authorization of write access to the second memory 10 , and sends the entered comparison data to the printing medium 1 via the communication unit 16 ( step 103 ). the ic chip 2 transfers the above comparison data received via the antenna unit 5 to the comparison unit 8 via the input - output controller 6 . ( step 111 in fig5 b ). the comparison unit 8 compares the received comparison data with the authentication data ( media data ) prestored in the first memory 9 , and decides from the comparison result whether data can be written into the second memory 10 ( step 112 ). if the comparison result indicates that the comparison data match the authentication data , the comparison unit 8 sends a write access permission signal through the input - output controller 6 and antenna unit 5 , notifying the image forming apparatus 11 that writing of data is possible , while sending the same notification to the access controller 7 in the ic chip 2 ( step 113 ). if the comparison result indicates that the comparison and authentication data do not match , the comparison unit 8 sends a write access denial signal through the input - output controller 6 and antenna unit 5 , notifying the image forming apparatus 11 that writing of data is not possible ( step 114 ). the communication unit 16 in the image forming apparatus 11 receives the comparison result sent from the ic chip 2 and transfers it to the controller 14 ( step 104 in fig5 a ), which decides from the comparison result whether data can be written or not ( step 105 ). if the comparison result indicates that data can be written , the controller 14 controls the image forming unit 17 to print the image data on the pre - fed printing medium 1 , and sends the price data to the printing medium 1 via the communication unit 16 ( step 106 ). if the above comparison result indicates that data cannot be written , the controller 14 returns the pre - fed printing medium 1 to the printer tray without printing ( step 107 ). if the ic chip 2 sends a write access permission signal ( in step 113 in fig5 b ), the price data received via the antenna unit 5 are sent to the access controller 7 via the input - output controller 6 ( step 115 ) and written into the second memory 10 by the access controller 7 ( step 116 ). if the ic chip 2 sends a write access denial signal ( in step 114 ), the price data are not written into the second memory 10 . fig6 a and 6b are flowcharts illustrating the reading of data in the first embodiment . fig6 a shows operations performed by the image forming apparatus 11 ; fig6 b shows operations performed by the ic chip 2 . the reading of data will be described below with reference to these flowcharts . first , the controller 14 in the image forming apparatus 11 receives a read request from the external device 12 via the input - output unit 13 ( step 201 in fig6 a ). the controller 14 then executes an embedded program that causes the operation panel 15 to display a prompt for entry of the comparison data necessary to authorize the reading of data from the second memory 10 , and sends the entered comparison data to the printing medium 1 via the communication unit 16 , while pre - feeding the printing medium 1 ( step 202 ). the ic chip 2 attached to the pre - fed printing medium 1 transfers the comparison data received via the antenna unit 5 to the comparison unit 8 via the input - output controller 6 ( step 211 in fig6 b ). the comparison unit 8 compares the received comparison data with the authentication ( media ) data prestored in the first memory 9 , and decides from the comparison result whether data can be read from the second memory 10 nor not ( step 212 ). if the comparison result indicates that the comparison and authentication data match , the comparison unit 8 sends a read access permission signal to the access controller 7 , and to the image forming apparatus 11 via the input - output controller 6 and antenna unit 5 , indicating that data can be read ( step 213 ). if the comparison result indicates that the comparison and authentication data do not match , the comparison unit 8 sends a read access denial signal to the image forming apparatus 11 via the input - output controller 6 and antenna unit 5 , indicating that data cannot be read ( step 214 ). when data can be read , the access controller 7 reads the price data stored in the second memory 10 and transfers the price data to the input - output controller 6 , which sends the transferred price data to the image forming apparatus 11 via the antenna unit 5 ( step 215 ). in the image forming apparatus 11 , the comparison result sent from the ic chip 2 is received by the communication unit 16 and transferred to the controller 14 ( step 203 in fig6 a ). the controller 14 then decides from the comparison result whether reading of data is possible or not ( step 204 ). if the comparison result indicates that reading of data is possible , the controller 14 receives the price data sent from the ic chip 2 attached to the pre - fed printing medium 1 via the communication unit 16 , converts the price data to data that can be displayed on the operation panel 15 by executing an embedded program , displays the converted data on the operation panel 15 ( step 205 ) and ejects the pre - fed printing medium 1 ( step 206 ). if the comparison result indicates that reading of data is not possible , the controller 14 displays an error message and ejects the pre - fed printing medium 1 ( step 206 ). as described above , according to the first embodiment , access to the data stored in the ic chip 2 is allowed only when entered comparison data match the authentication data prestored in the ic chip 2 , whereby access to the ic chip 2 can be restricted and the secrecy of the data stored therein can be improved , making the counterfeiting process more difficult . fig7 is a block diagram showing the internal structure of the ic chip in the second embodiment of the invention . the ic chip 26 in fig7 corresponds to the ic chip 2 of the printing medium 1 in the first embodiment shown in fig1 . the image forming apparatus in the second embodiment of the invention is identical to the image forming apparatus in the first embodiment shown in fig3 and 4 . as shown in fig7 , the ic chip 26 comprises an antenna unit 19 , an input - output controller 20 , a first access controller 21 , a second access controller 22 , a comparison unit 23 , a first memory 24 , and a second memory 25 . the operations of these blocks are similar to those of the antenna unit , input - output controller , access controller , comparison unit , first memory , and second memory in the first embodiment described above . as in the first embodiment , the ic chip 26 uses a contactless communication system in which data are transmitted and received from the antenna unit 19 via the loop antenna 4 shown in fig1 . the antenna unit 19 also supplies power received via the loop antenna 4 to the ic chip 26 . the input - output controller 20 controls the input and output of data received and transmitted from the antenna unit 19 . the first access controller 21 and second access controller 22 control access to the data stored in the ic chip 26 . the comparison unit 23 decides whether access to the data stored in the ic chip 26 is authorized or not . the first memory 24 and second memory 25 are both nonvolatile memories permitting read and write access , and the first memory 24 permits repeated write access . authentication data used in decision making by the comparison unit 23 are stored in the first memory 24 ; the authentication data include both prestored authentication data and additional data transmitted and received as described above ; validation data transmitted and received as described above are stored in the second memory 25 . the printing medium 1 incorporating the ic chip 26 in the second embodiment may be used for various purposes . to address the problems of the prior art described above , as in the first embodiment , it will be assumed that the printing medium 1 is used for printing a negotiable security . repeated descriptions of the image forming apparatus will be omitted , since this apparatus was described in the first embodiment . to make the printing medium 1 shown in fig1 into a negotiable security incorporating the ic chip 26 in the second embodiment , two processes must be performed : first , the title and other information of the security must be printed on the printing medium 1 , and second , information that can certify the validity of the printing medium 1 when it is used as a negotiable security must be stored in the second memory 25 of the ic chip 26 as validation data . the validity of the negotiable security is verified by comparing the information printed on the printing medium 1 with the validation data stored in the second memory 25 . the validation data are stored in the second memory 25 when an image is printed on the printing medium 1 , to certify the validity of the image printed on the printing medium 1 . as in the first embodiment , it is assumed that the information printed on the printing medium 1 includes at least the price of the negotiable security , and that the price data are used as validation data . in practice , the validation data may be any data that can be compared with the image printed on the printing medium 1 to verify the image . instead of price data , the validation data may be , for example , issuer data , owner data , or issue date data , or an encrypted form of any of these data . to write the validation data when the external device 12 requests printing of the negotiable security by sending the printing data , the comparison unit 23 first decides whether to permit write access to the second memory 25 . if write access is permissible , the input - output controller 20 transfers additional data received via the antenna unit 19 to the first access controller 21 , and transfers validation data , also received via the antenna unit 19 , to the second access controller 22 . the first access controller 21 writes the additional data into the first memory 24 , appending the additional data to the authentication data already stored in the first memory 24 ; the second access controller 22 writes the validation data into the second memory 25 . if write access is not permissible , the additional data and validation data are not received and written . the authentication data prestored in the first memory 24 are used to decide whether these write accesses to the first and second memories 24 , 25 are permissible . these authentication data are prestored in the first memory 24 before the ic chip 26 is attached to the printing medium 1 , and do not include the additional authentication data appended later . the prestored authentication data may be any data associated with the printing medium 1 , such as data identifying the manufacturer of the ic chip 26 , data identifying the security issuer who performs printing on the printing medium 1 , data identifying the media type of the printing medium 1 , or serial number data . in this second embodiment , as in the first embodiment , data identifying the media type of the printing medium 1 ( media data ) are employed as the prestored authentication data . to read the validation data when the external device 12 requests reading of data to verify the authenticity of the negotiable security , the comparison unit 23 first decides whether read access to the validation data stored in the second memory 25 is permissible . if read access is permissible , the second access controller 22 reads the validation data from the second memory 25 and transfers the validation data to the input - output controller 20 , which transmits the transferred data via the antenna unit 19 . if read access is not permissible , reading and transmitting of the validation data are not carried out . both the authentication data prestored in the first memory 24 and the additional data appended to the prestored authentication data are used to decide whether the above read access is possible or not . the additional data appended to the prestored authentication data may be any data associated with the printing medium 1 or the image printed on the printing medium 1 , such as data identifying the manufacturer of the ic chip 26 , data identifying the security issuer who performs printing on the printing medium 1 , data identifying the media type of the printing medium 1 , data identifying the owner of the image printed on the printing medium 1 or a person having right of access thereto , or serial number data . in the description below , data identifying the owner of the image printed on the printing medium 1 or a person having right of access thereto ( authorization data ) are employed as the additional data . as described above , the authenticity of the negotiable security in the second embodiment is verified as in the first embodiment , by reading the validation data stored in the second memory 25 , but the decision as to whether to permit read access to the second memory 25 is made on the basis of both the authentication data prestored in the first memory 24 and the authorization data appended as additional authentication data when the negotiable security was printed on the printing medium 1 . in the second embodiment , therefore , a person attempting to perform read access must be in possession of both the prestored authentication data ( in this case , media data ) and the additional data ( in this case , authorization data ). the controller 14 in the image forming apparatus 11 , shown in fig3 and 4 , receives printing data from the input - output unit 13 , and converts the received printing data into image data to be printed on the printing medium 1 , authorization data to be additionally stored in the first memory 24 , and security price data to be stored in the second memory 25 . the communication unit 16 transmits both the authorization data and the security price data to the ic chip 26 . aside from these differences , the image forming apparatus 11 operates as described in the first embodiment . the flowcharts in fig5 a and 5b , which illustrate the printing of an image and writing of data in the first embodiment , also describe the printing and writing operations in the second embodiment , because these operations are the same as in the first embodiment , except for modifications made necessary by the authorization data . the modifications will be explained in the description below . fig5 a shows operations performed by the image forming apparatus 11 ; fig5 b shows operations performed by the ic chip 26 . first , the controller 14 in the image forming apparatus 11 receives printing data from the external device 12 via the input - output unit 13 ( step 101 in fig5 a ). while pre - feeding the printing medium 1 , the controller 14 converts the received printing data by executing an embedded program to generate image data to be printed on the printing medium 1 and price data to be sent to the printing medium 1 ( step 102 ). after completion of the above data conversion , the controller 14 requests the entry on the operation panel 15 of comparison data necessary for authorization of write access to the first memory 24 and second memory 25 , and sends the entered comparison data to the printing medium 1 via the communication unit 16 ( step 103 ). the ic chip 26 transfers the above comparison data , which are received via the antenna unit 19 , to the comparison unit 23 via the input - output controller 20 ( step 111 in fig5 b ). the comparison unit 23 compares the received comparison data with the authentication data ( media data ) prestored in the first memory 24 , and decides from the comparison result whether to permit data to be written into the second memory 25 ( step 112 ). if the comparison result indicates that the comparison data match the authentication data , the comparison unit 23 sends a write access permission signal through the input - output controller 20 and antenna unit 19 to notify the image forming apparatus 11 that writing of data is possible , while sending the same notification to the first access controller 21 and second access controller 22 in the ic chip 26 ( step 113 ). if the comparison result indicates that the comparison and authentication data do not match , the comparison unit 23 sends a write access denial signal through the input - output controller 20 and antenna unit 19 to notify the image forming apparatus 11 that writing of data is not possible ( step 114 ). the communication unit 16 in the image forming apparatus 11 receives the comparison result sent from the ic chip 26 and transfers it to the controller 14 ( step 104 in fig5 a ), which decides from the comparison result whether data can be written or not ( step 105 ). if the comparison result indicates that data can be written , the controller 14 controls the image forming unit 17 to print the image data on the pre - fed printing medium 1 , and sends the authorization data and price data to the printing medium 1 via the communication unit 16 ( step 106 ). if the above comparison result indicates that data cannot be written , the controller 14 returns the pre - fed printing medium 1 to the printer tray without printing ( step 107 ). if the ic chip 26 sends a write access permission signal ( in step 113 in fig5 a ), the above authorization data and price data , which are received via the antenna unit 19 , are sent to the first access controller 21 and second access controller 22 , respectively , via the input - output controller 20 ( step 115 ). the first access controller 21 writes the authorization data into the first memory 24 ; the second access controller 22 writes the price data into the second memory 25 ( step 116 ). if the ic chip 26 sends a write access denial signal ( in step 114 ), no data are written into the first memory 24 and second memory 25 . the flowcharts in fig6 a and 6b , which illustrate the reading of data in the first embodiment , also illustrate the reading operation in the second embodiment because the reading operation is the same as in the first embodiment except for modifications made necessary by the authorization data . these modifications will be explained in the description below . fig6 a shows operations performed by the image forming apparatus 11 ; fig6 b shows operations performed by the ic chip 26 . first , the controller 14 in the image forming apparatus 11 receives a read request from the external device 12 via the input - output unit 13 ( step 201 in fig6 a ). the controller 14 then executes an embedded program that causes the operation panel 15 to display a prompt for entry of the comparison data necessary to authorize the reading of data from the second memory 25 . after the operator of the image forming apparatus 11 enters the comparison data , the controller 14 sends the comparison data to the printing medium 1 via the communication unit 16 , while pre - feeding the printing medium 1 ( step 202 ). the entered comparison data must include both the prestored authentication data and the additional authorization data . the ic chip 26 attached to the pre - fed printing medium 1 transfers the comparison data received via the antenna unit 19 to the comparison unit 23 via the input - output controller 20 ( step 211 in fig6 b ). the comparison unit 23 compares the received comparison data with the data ( including the authorization data ) stored in the first memory 24 , and decides from the comparison result whether data can be read from the second memory 25 nor not ( step 212 ). if the comparison result indicates that the comparison data match the authentication data and additional data stored in the first memory 24 , the comparison unit 23 sends a read access permission signal to the second access controller 22 , and to the image forming apparatus 11 via the input - output controller 20 and antenna unit 19 , indicating that data can be read ( step 213 ). if the comparison result indicates that the comparison data and stored data do not match , the comparison unit 23 sends a read access denial signal to the image forming apparatus 11 via the input - output controller 20 and antenna unit 19 , indicating that data cannot be read ( step 214 ). when data can be read , the second access controller 22 reads the price data stored in the second memory 25 and transfers the price data to the input - output controller 20 , which sends the transferred price data to the image forming apparatus 11 via the antenna unit 19 ( step 215 ). in the image forming apparatus 11 , the comparison result sent from the ic chip 26 is received by the communication unit 16 and transferred to the controller 14 ( step 203 in fig6 a ). the controller 14 then decides from the comparison result whether reading of data is permissible or not ( step 204 ). if the comparison result indicates that reading of data is permissible , the controller 14 receives the price data sent from the ic chip 26 of the pre - fed printing medium 1 via the communication unit 16 , converts the price data to data that can be displayed on the operation panel 15 by executing an embedded program , displays the converted data on the operation panel 15 ( step 205 ) and ejects the pre - fed printing medium 1 ( step 206 ). if the comparison result indicates that reading of data is not permissible , the controller 14 displays an error message and ejects the pre - fed printing medium 1 ( step 206 ). as described above , the second embodiment provides a further degree of protection against counterfeiting by requiring the counterfeiter to know two types of data ( authentication data and authorization data ) that cannot be read from the ic chip 26 . in particular , the authorization data can be uniquely determined by the person who operates the input - output unit 13 when the original negotiable security is printed on the printing medium 1 , making it very difficult for the counterfeiter to determine what the authorization data are . in the first and second embodiments , the communication region 18 in which the image forming apparatus 11 and printing medium 1 can communicate with each other is located in the area into which the printing medium 1 is pre - fed , but the communication region 18 may be located anywhere , provided the location enables the image forming apparatus 11 to reliably distinguish the printing medium 1 with which it wants to communicate from other printing media stacked in the printer tray . the ic chip may also be mounted anywhere on the printing medium 1 as long as the ic chip is located in the communication region 18 during the time when communication must take place . the above embodiments have been described in relation to the printing of a negotiable security , but the present invention can also be practiced with other matter printed on printing media that can store electronic data , especially if the printed matter is printed , read , and written exclusively by a particular administrative organization . such printed matter includes various kinds of certificates and tickets , business documents such as contracts and applications , and copyright matter using paper media such as posters and compact disc ( cd ) jackets those skilled in the art will recognize that further variations are possible within the scope of the invention , which is defined in the appended claims .