JPH02120951A - Secret data storage device - Google Patents

Abstract

PURPOSE:To efficiently and surely write secret data without reducing safeness by including a function for erasing initial information after checking the existence of the initial information and then writing secret data in a single integrated circuit element. CONSTITUTION:When an external write request signal and secret data are inputted, a central control part 3 outputs a comparison request signal to a write enable decision part 7 and the decision part 7 reads out data contents in a memory area for writing the secret data of a secret data memory 5 and compares the read contents with reference initial information to check their coincidence. The central control part 3 stores the secret data in the memory area writing the initial information instead of the initial information through a data bus 11. Even when an external write request is inputted to the central control part 3 thereafter, coincidence with the initial information can not be obtained and data writing in the cipher data memory 5 is disabled. Thus, a secret code can be efficiently and surely written.

Description

[Detailed description of the invention] The purpose of the invention (Industrial application field) The present invention relates to a secret data storage device.

(Prior Art) As one of the results of the development of electronic technology in recent years, IC cards that have a built-in CPU and memory are attracting attention. IC cards are a medium that is expected to be used by individuals in the near future and utilized in a wide range of fields due to the controllability provided by the built-in CPtJ and the enormous amount of information stored in the memory.

By the way, when it comes to IC cards, it is important to prevent fraud, etc. that may occur as a result of their future versatility. It is necessary to memorize secret codes, and countermeasures against this are an important issue in realizing the general use of IC cards. As a countermeasure against this, for example,
There is a technique disclosed in Japanese Patent No. 348. This technique has M+N storage f,>'L locations in an integrated circuit device that separately store M-bit specific encryption keywords and N-bit activation codewords used for the program;
+N bits are initially set to a first binary value in an external programmable read-only storage register; energizing the register to enable the specific encryption keyword to be written to M storage locations in the register, and subsequently converting the N-bit energized codeword to a predetermined second binary value. The gist of the present invention is to include gate means for permanently deactivating the M+N values by preventing the M+N values from being changed.

(Problem to be Solved by the Invention) However, in the disclosed technique described above, since an N-bit activation code is required for writing secret data, it is possible to write the secret code accordingly. There is a problem that the capacity decreases, and since this energizing code is deactivated after writing and is not used, there is a possibility that the memory is used inefficiently or that writing cannot be performed reliably.

Note that here, we have explained using an IC card as an example, but
Similar problems arise in those that perform processing using confidential information limited to this.

The present invention has been made in view of the above, and an object of the present invention is to provide a secret data storage device in which secret data can be written efficiently and reliably without reducing security.

[Structure of the Invention (Means for Solving the Problems)] To achieve the two objectives, the present invention provides a device configured in a single integrated circuit element and having the function of storing secret data from outside. a non-volatile storage means for storing at least initial information and secret data, and a write permission for detecting that the initial information is stored in the storage means and outputting a write permission signal when writing the secret data is requested. The gist of the present invention is to include a determining means, and a write control means for erasing initial information and writing secret data in the storage means upon receiving a write permission signal.

(Function) In the secret data storage device according to the present invention, focusing on the fact that the contents of the nonvolatile memory can be set to a specific value during the manufacturing process, the content of the nonvolatile memory is set to a specific value when writing secret data. After confirming the existence of corresponding initial information, the function of erasing this initial information and writing the secret data is configured in a single integrated circuit element.

(Example) Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a block diagram of a secret data storage device according to an embodiment of the present invention. The secret data storage device according to this embodiment is configured in an integrated circuit element 1 and includes a central control section 3, a secret data memory 5, a write permission determination section 7, and a verify section 9.

The secret data memory 5 constitutes a non-volatile storage means,
It stores secret data from outside. Note that, in the memory area for storing this secret data, initial information indicating that no writing has been done yet is stored before the secret data is written. This initial information is set to a predetermined value during the manufacturing process.

The write permission determination unit 7 receives a comparison request signal that is output when the central control unit 3 receives an external write request signal for secret data from the outside, and detects the presence or absence of initial information in the secret data memory 5. This allows the central control unit 3 to write secret data when the initial information is stored.

The verifying section 9 determines whether the writing of the secret data into the secret data memory 5 by the central control section 3 has been done reliably.

The central control section 3 constitutes a write control means, and has a function of controlling the operations of the secret data memory 5, the write permission determination section 7, and the verify section 9.

Next, the operation of this embodiment will be explained using the timing chart shown in FIG. In Figure 2, (A) and (
B) is an external write request signal to the central control unit 3 and write data including secret data, (C) is a comparison request signal, (D) is a read request signal to the secret data memory 5, and (E) is write permission. A comparison result flag signal indicating the processing result in the determination unit 7, (F) is an internal write request signal from the central control unit 3 to the secret data memory 5, (G) is a data signal to the data bus 11-, (H) is a central Verification request signal from control unit 3 to verification unit 9, (I)
indicates a verify result signal indicating a processing result in the verify section 9.

Now, when an external write request signal and secret data are manually inputted to the central control unit 3 from the outside in order to write the confidential data (Fig. 2 (A) and (B)), the central control unit 3 immediately starts writing. A comparison request signal is output to the permission determination unit 7 (FIG. 2(C)).

When the write permission determination unit 7 receives this comparison request signal, it outputs a read request request to the confidential data memory 5.The signal a) in FIG. The data contents of the area are read (data a in FIG. 2(G)). Before writing the secret data F, the initial information stored in advance at the time of manufacturing the memory should have been written, so the write permission determination unit 7 compares this with the reference initial information stored internally in advance. It compares and confirms whether they match, and outputs a comparison result flag signal indicating that writing is possible to the central control unit 3 (FIG. 2(E)).

When the central control unit 3 receives this comparison result flag signal,
Outputs an internal write request signal to the secret data memory 5 (
2(F)), writing of secret data is started via the data bus 11 (data b and data d in FIG. 2(G)). Here, the secret data is
The initial information is stored in the memory area where the initial information was written in place of the initial information. Therefore, the central control unit 3 outputs a verify request signal to the verify unit 9 at the same time as writing starts ((H) in FIG. 2). The verify unit 9 sequentially requests the secret data memory 5 to read the written data in response to the writing by the central control unit 3, detects a match with the data written to the central control unit 3 (second figure(
D) and signal C9 data C and data e) in FIG. 2 (G) are output to the central control unit 3 as a verify result signal indicating that writing has been completed correctly (FIG. 2 (■)) . As a result, the central control unit 3 ends the writing.

After this, even if an external write request is made manually to the central control unit 3 (Fig. 2 (A), (B)), the initial information will not match in the processing of the write permission determination unit 7. Therefore, the fact that writing is not possible is outputted as a comparison result flag signal, and writing to the encrypted data memory 5 becomes impossible.

Therefore, according to this embodiment, a secret code can be written in a reliable and reliable manner without requiring any energizing code unlike the prior art.

In this embodiment, the write control may be executed by hardware, or may be executed by software under the control of the CPU. Specifically, as shown in FIG. 3, for example, a write program 23, a verify program 25
The ROM 2 includes a program load program 31 for loading these control programs 27 into the RAM 29, and a write permission determination block 33 for detecting storage of initial information in the secret data memory 5. shall be. Then, when +e to the CPUB 5 and a program load request signal for writing confidential data are input manually, the CPU 35 confirms the storage of the initial information in the confidential data memory 5 based on the write permission determination program 33, and then executes the program load request signal for writing confidential data. 1. The load program 31 loads the write program 23, the verify program 25, and the control program 27 onto the RAM 17, and based on these, writes secret data from the outside into the secret data memory 5. Therefore, if the storage of the initial information cannot be confirmed while the write permission determination program 33 is being executed, the program load program 31 will not be executed and therefore the write process will not be performed. In this modification, it is easy to erase the program loaded into the RAM 29 by turning off the power after writing the confidential data, and the security is high. In addition, in FIG. 3, 37 is an interface between the CPU 35 and the secret data memory.

[Effects of the Invention] As explained above, according to the present invention, focusing on the fact that the contents of a non-volatile memory can be set to a specific value during the manufacturing process, this specific value is set when writing confidential data. After confirming the existence of initial information corresponding to a value, the function of erasing this initial information and writing the secret data is configured in a single integrated circuit element, reducing the security of writing secret data. (It can be done efficiently and reliably.)

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of one embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of FIG. 1, and FIG. 3 is a diagram showing another embodiment of the present invention.

Claims (1)

[Scope of Claim] A device configured in a single integrated circuit element and having a function of storing secret data from the outside, comprising a non-volatile storage means for storing at least initial information and secret data; write permission determination means that detects that initial information is stored in the storage means at the time of a data write request and outputs a write permission signal; and upon receiving the write permission signal, erases the initial information from the storage means and makes it confidential A secret data storage device comprising: a write control means for writing data;