JP3231448B2 - IC card - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IC card, and more particularly to a method of adding an error check code to a directory used for managing files.

[0002]

2. Description of the Related Art As a new information recording medium replacing a magnetic card, an IC card has attracted attention. This IC card has a built-in memory element, has a remarkably improved information storage capacity as compared with a magnetic card, and has a high level of security. Normally, a plurality of file areas are defined in a memory area of an IC card, and various information is written in a predetermined file area in units of records. Also,
A directory is prepared for each file, and information necessary for accessing the file (for example, file ID, access condition, start address value of file area, record length, number of recorded records, Information, etc.) is written.

[0003]

An IC card used in general social life records information that is very important in social life. Therefore, it is necessary to take safety measures to prevent the loss of recorded information due to any accident. For this reason, records and directories are recorded together with error check codes, so that even if data is garbled, it can be detected. That is, at the time of reading, the error check code is read together with the record and the directory, and a process of performing a predetermined logical operation to confirm that the error check code is correct is performed. However, such an error check process takes longer as the data length to be checked becomes longer. In particular, the directory is information to be read every time a file is accessed, and the load of error check processing is considerably heavy, and the computation time spent for this is not negligible.

Accordingly, the present invention provides an IC that can reduce the load of error check processing for a directory.
The purpose is to provide the card.

[0005]

[Means for Solving the Problems]

(1) The first invention of the present application is an IC card that records data in a file unit and records information necessary for accessing the file as a directory. In the IC card, the information in the directory is rewritten. Grouping is performed based on frequency, and a separate error check code is added to each group and recorded.

(2) The second invention of the present application is directed to the IC card according to the first invention, wherein the information in the directory is used to access the fixed information that does not need to be rewritten after the IC card is issued and the file. Security information including necessary keys and variable information including information on the number or size of records in the file at the present time are grouped into groups, and a separate error check code is added to each group and recorded. It is.

[0007]

[Operation] In the directory, various information necessary for accessing a file is recorded. Some of these pieces of information do not need to be rewritten at all at the time of issuing the IC card, and some pieces of information need to be rewritten from time to time during use of the IC card. Some information needs to be rewritten frequently during the use of. In the IC card according to the present invention, the information in the directory is divided into groups based on the rewriting frequency of the information, and a separate error check code is added to each group. In general, it is considered that the higher the frequency of data rewriting, the higher the probability of occurrence of errors such as data corruption, and conversely, the lower the frequency of data rewriting, the lower the probability of occurrence of errors such as data corruption. Therefore, it is usually sufficient to perform only the error check processing for the group having a high rewrite frequency. The error check process for the group with a low rewrite frequency may be appropriately performed as needed. By doing so, the load of the normal error check processing can be greatly reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. Here, the EEPRO built in the IC card
A case where information is recorded in M will be described as an example. When an IC card is issued, as shown in FIG. 1, several file areas are defined on the memory area of the EEPROM, and a directory is created for each file. In the illustrated example, two areas of a file A and a file B are defined, and a directory A and a directory B are prepared at the same time. Information necessary for accessing the file A is written to the directory A, and information necessary for accessing the file B is written to the directory B.

In a conventional IC card, an error check code is added to an entire directory. Therefore, it is necessary to perform the error check process for one entire directory. If the data length of one directory is long, the number of digits to be subjected to the error check process becomes large, and a considerably long processing time is required.

The gist of the present invention is that information in a directory is divided into groups based on the rewriting frequency of the information, and a separate error check code is added to each group and recorded. This will be described based on the specific embodiment of FIG. In this embodiment, one directory is divided into three groups. In Group 1, fixed information that does not need to be rewritten after the IC card is issued is recorded. For example, information such as a file ID and an access condition of the file is included in the fixed information. These pieces of information are written when the IC card is issued, but are not rewritten when the card is used.
In the next group 2, security information including a key necessary for accessing the file is recorded. Such keys are not frequently rewritten. It is only rewritten in special cases, such as when the user wants to change the key. In the last group 3, variable information that is frequently rewritten is recorded. For example,
Information such as the number of records in the file, the recorded capacity, and the remaining capacity at the current time. If you add or delete records in the file, information about the number and size of records will change,
Each time, rewriting is performed.

After all, in FIG. 2, the fixed information of group 1 is information that is not rewritten when the IC card is used, the security information of group 2 is information with a low rewriting frequency, and the variable information of group 3 is Can be said to be information with a high rewrite frequency. In the present invention, each of the grouped information is recorded with an independent error check code added thereto. That is, the fixed information has the error check code ECC1, the security information has the error check code ECC2, and the variable information has the error check code ECC1.
C3 is added and recorded, and the error check process can be performed separately and independently for each group. For example, the error check processing for the group 3 generates an error check code by performing a predetermined logical operation on the data of the variable information portion of the read directory, and generates the error check code. What is necessary is just to confirm whether or not it matches ECC3. Since the necessary logical operation need only be performed on the data of the variable information portion, the number of digits of the data is relatively short, and the operation load is reduced.

In general, it is considered that the higher the frequency of rewriting data, the higher the probability of occurrence of errors such as data corruption, and conversely, the lower the frequency of data rewriting, the lower the probability of occurrence of errors such as data corruption. Therefore, in the example of FIG. 2, it is considered that the error occurrence probability is extremely low for the fixed information that is not rewritten. Therefore, it is sufficient to perform the error check processing for group 1 only when it is deemed necessary. On the other hand, for variable information that is frequently rewritten, the error occurrence probability is considered to be higher. Therefore, it is preferable that the error check process for group 3 be performed frequently. Specifically, each time the directory is read, the group 3
It is sufficient to always perform the error check processing for. For security information, the error check process may be performed at this intermediate frequency. As described above, if the information in the directory is grouped according to the rewriting frequency and the error check can be performed for each group, a very efficient error check process can be performed.

Although the present invention has been described based on the illustrated embodiment, the present invention is not limited to this embodiment, but can be implemented in various other modes. In particular, the grouping shown in FIG. 2 is an example, and the number of groups can be set arbitrarily, and which information belongs to which group is also arbitrary. In short, any grouping method may be adopted as long as grouping based on the expected frequency of rewriting is performed.

[0014]

As described above, according to the IC card according to the present invention, the information in the directory is grouped according to the rewriting frequency, and the error check can be performed for each group. The burden of the check process can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing files and directories defined in an EEPROM when an IC card is issued.

FIG. 2 is a diagram showing an example of a format in which the directories shown in FIG. 1 are grouped and recorded based on the present invention.

[Explanation of symbols]

 A, B ... area and directory ECC1, ECC2, ECC3 ... error check code

Continuation of the front page (56) References JP-A-4-165487 (JP, A) JP-A-63-225886 (JP, A) JP-A-62-8282 (JP, A) (58) Fields studied (Int .Cl. ⁷ , DB name) G06K 19/07 G06F 12/00 542

Claims (2)

(57) [Claims] 1. An IC card for recording data in file units and recording information necessary for accessing the file as a directory, wherein information in the directory is grouped based on the rewriting frequency of the information. An IC card which is divided and recorded with a separate error check code for each group. 2. The IC card according to claim 1, wherein
The information in the directory includes fixed information that does not need to be rewritten after the IC card is issued, security information including a key required to access the file, and variable information including information on the number of records or the capacity of the file at the present time. An IC card characterized in that the data is divided into groups, and each group is recorded with a separate error check code added.