JP2000029791A - Method for encoding and decoding of information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the capability of protecting the secrecy of information recorded on an information recording medium without making device constitution complicated, even when only one encoding key is used by selecting and substituting a new encoding key for a fixed encoding key according to information obtained, when the information recording medium is accessed. SOLUTION: Scramble data s'WD encoded, including the mathematical values, digits, and blocks of non-scramble data WD in the encoding key as specified by one encoding key selected out of predetermined encoding keys, according to the time data Dc and access frequency Da when the information storage medium 1 is accessed are generated and recorded on the information recording medium 1. For decoding, decoding keys K1 to Kn in an encoding key code function table 31 are scanned. Then when the encoding key K1' read out of the descramble data RD and the encoding key K1 set at the time of the scanning match each other, it is decided that the recorded information is correct.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for encrypting predetermined information and an encryption key using an encryption key, recording the encrypted information on an information recording medium, and reading and decoding the recorded content. Each time the information recording medium is accessed, the information is replaced with a new encryption key and the information is newly encrypted, thereby making it difficult to decipher the information by eavesdropping and increasing the confidentiality of the information recording medium. And a decoding method.

[0002]

2. Description of the Related Art A magnetic card, an IC card, or the like is used as an information recording medium on which information can be recorded, updated, and read, but information is encrypted to protect the secret of the information. Have been done. For example, a system in which encryption and decryption of information is performed only when the encryption key recorded on the information recording medium is compared with the encryption key of the system using the information recording medium, and as a result, they match. There is. Encryption key
In a complicated system, for each function, for example, a verification function for verifying the validity of the card owner, an authentication function for verifying the validity of the card itself, a function for writing encrypted information to the card, etc. Although it may be set, in a simple system, encryption and decryption are usually processed by one key. In such a system, in order to prevent a malicious person from analyzing cryptographic information including an encryption key and using the information to decrypt confidential information, such information is used using pseudo-random numbers. There is known an encryption method or the like that cannot be decrypted unless it is encrypted or dispersed into some information and a certain number or more of the distributed information is collected. However, since the system is complicated, in a simple system, a method of scrambling by exchanging or exchanging information digits, blocks, and the like according to a certain rule is often adopted.

FIG. 2 is a block diagram showing an example of an apparatus for implementing a conventional method for encrypting and decrypting an information recording medium. This example is a system that realizes a simple encryption and decryption method in which the encryption key is one fixed value. As shown in FIG. 1, the system includes an information recording medium 1 for holding encrypted information, and a reader / writer 2 for reading and recording the encrypted information on the information recording medium 1.
And a scrambler / descrambler 3 for encrypting and decrypting information based on the encryption key. More specifically, the scrambler / descrambler 3 uses non-scrambled data (W
D) and the descrambled data (R
D) and a data digit processing circuit 35 inserted in series between the input / output terminal of the data buffer 32 for holding the data and the input / output terminal of the reader / writer 2. And a data block processing circuit 36; a scramble control unit 33 for controlling the processing of these three processing circuits and the reader / writer 2 to encrypt and decrypt information via the information recording medium 1; A scramble control unit 37 and a fixed encryption key for outputting a fixed encryption key and a fixed encryption key code function to a predetermined circuit based on a descrambling start signal.
It comprises a code function table 39 and an encryption key collation circuit 38.

This system employs a simple encryption and decryption method in which the encryption key is one fixed value (Kf), and the non-scramble data is specified as specified by the encryption key. The scrambled data obtained by encrypting the arithmetic value of (WD), the digit, and the block including the encryption key.
(S'WD) is generated and recorded on the information recording medium, and the encrypted information (s'RD) recorded on the information recording medium is read out and decrypted by using the same encryption key. It reversely generates scrambled data (RD), and uses a prepaid card, an entrance / exit card or the like as an information recording medium. The information recorded on these cards has a common fixed encryption key, and the prepaid card has an issuance amount, time data, and the number of times of access (for example, zero) at the time of issuance of a ticket.
Is recorded and handed over to the user, but every time the user accesses the system by using this card, the used amount and balance of the card, time data, and the number of times of access are updated. The entry / exit card is first recorded with the user's ID, time data and the number of accesses (for example, zero) and is issued to the user. Each time the user enters / exits by this card, the card is entered.
The time data of the code, the use time, the number of accesses and the like are updated. Therefore, here, other than the fixed encryption key (Kf), the time data (Dc), and the number of times of access (Da) which are considered to be commonly used in the system, other data are collectively used. (Dn). Hereinafter, the operation of the conventional example shown in FIG. 2 will be described in detail separately for data encryption and decryption.

In order to generate encrypted scrambled data (S'WD) from non-scrambled data (WD) and record it on the information recording medium 1, first, a fixed encryption key code function table is used. The non-scrambled data (W) together with the time data (Dc), the number of accesses (Da) and other data (Dn) are obtained by the fixed encryption key (Kf) of the cable 39.
D) is formed and written into the data buffer 32, and at the same time, the scramble control unit 33 is set to an operable state. Next, the fixed key of the fixed encryption key code function table 39 is used.
A scramble control unit 33 based on a code function Fs (Kf)
When the scramble parameter is written in the register, the scramble control unit 33 sequentially controls the data arithmetic value processing circuit 34, the data digit processing circuit 35, and the data block processing circuit 36 to perform non-scramble data (WD). The scrambled data (S'WD) is created by applying a predetermined scramble to the arithmetic value, digit, and block of the scrambled data, and the scramble data (S'WD) is generated. The information is recorded on the information recording medium 1.
At this time, the specific contents of the information recorded at the time of issuing and updating the information recording medium 1 include those shown in the examples of the prepaid card and the entrance / exit card.

In order to read out the scrambled data (S'WD) encrypted on the information recording medium 1 and to decrypt the descrambled data (RD), first, the reader / writer 2 The descrambling control unit 37 is set in an operable state by the encryption key (Kf) of the fixed encryption key code function 39 in response to the descrambling start signal. next,
Fixed encryption key code Fixed key code of function table 39
When the descrambling parameter is written to the descrambling control unit 37 by the function Fd (Kf), the descrambling control unit 37 sequentially operates the data block processing circuit 36, the data digit processing circuit 35, and the arithmetic value processing circuit 34. A predetermined descramble is applied to the block, digit, and arithmetic value of the scrambled data (S'RD) read under control to decode the data, and inversely generate descrambling data (RD) to obtain a data buffer. 32 and a fixed encryption key read from the output signal of the data buffer 32.
(Kf ') is sent to the encryption key collation circuit 38 and collated with the fixed encryption key (Kf). If the collation result matches, the record information of the information recording medium 1 is determined to be correct. It is determined to be illegal. When a verify check of the scrambled data (S'WD) recorded on the information recording medium 1 is performed, all the remaining descrambling data (RD) are unsynchronized when the above-mentioned encrypted key collation results match. What is necessary is just to collate with the scramble data (WD) and confirm the coincidence.

[0007]

However, the conventional method for encrypting an information recording medium as described above has the following problems. Since the encryption key is one fixed value, even if the information including the encryption key is scrambled, the access is repeated and the change of the data value is observed, whereby the encryption key is decrypted and encrypted. Information may be revealed. SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems related to the conventional information recording medium encryption and decryption methods as described above, and provides a new encryption method based on information at the time of accessing the information recording medium. By selecting a key and replacing it with a fixed encryption key, the encryption key
It is an object of the present invention to provide an information recording medium encryption method capable of enhancing the secret protection capability of information recorded on the information recording medium without complicating the configuration of the device even if there is only one device. .

[0008]

In order to achieve the above-mentioned object, according to the present invention, there are provided (1) predetermined information using an encryption key and encrypted information obtained by encrypting the encrypted key. In the method of encrypting an information recording medium for recording on an information recording medium, data obtained when accessing the information recording medium is used as one new encryption from a plurality of encryption keys determined in advance as parameters. And updating the recorded content of the information recording medium with new encryption information obtained by encrypting the predetermined information and the new encryption key by selecting an encryption key and replacing the encryption key with the encryption key. (2) encryption means for the information recording medium according to (1), wherein the time data obtained when the information recording medium is accessed is used as a parameter; When accessing the information recording medium The number of accesses to be parameter - the the motor (1) is an encryption means described information recording medium. Further, in (4) a method for decrypting predetermined information and an encrypted information obtained by encrypting the encrypted key using the encryption key from the information recording medium, a plurality of predetermined information decryption methods may be used. Encryption keys are selected one by one from the encryption keys, and the encryption information recorded on the information recording medium is sequentially decrypted, and the set encryption key and the decrypted encryption key are selected. Means for enabling reading of the encrypted information when-is matched.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 1 is a block diagram showing an embodiment of an apparatus for realizing an information recording medium encryption and decryption method according to the present invention. Although the present embodiment is a simple encryption method with one encryption key, it replaces the encryption key with a new value each time the information recording medium is accessed, so that the encryption key by eavesdropping of information is obtained. It is a system that makes it extremely difficult to decipher and enhances the ability to keep information confidential. As shown in FIG. 1, the system includes an information recording medium 1 for holding encrypted information, a reader / writer 2 for reading and recording the encrypted information on the information recording medium 1, and an encryption key. And a scrambler / descrambler 3 for encrypting and decrypting information based on. More specifically, the scrambler / descrambler 3 stores data for holding non-scramble data (WD), which is original information not to be encrypted, and descramble data (RD), which is decrypted information. A data arithmetic processing circuit 34, a data digit processing circuit 35 and a data block processing circuit 3 inserted in series between the input / output terminal of the data buffer 32 and the input / output terminal of the reader / writer 2.
6, a scramble control unit 33 and a descramble control unit 37 for processing and controlling these three processing circuits and the reader / writer 2 to encrypt and decrypt information via the information recording medium 1; An encryption key function table 31 for outputting an encryption key function to a predetermined circuit based on an encryption key and a descrambling start signal, and an encryption key verification circuit 38. Have been.

This system employs a simple encryption and decryption method of selecting one of a plurality of encryption keys and encrypting and decrypting information. Time data when the medium 1 is accessed (D
c) and / or non-scrambled data (WD) as specified by one encryption key selected from a plurality of encryption keys predetermined based on the number of accesses (Da).
The scrambled data (s'WD) is generated by encrypting the arithmetic value, digit, and block including the encryption key, and is recorded on the information recording medium 1. When the encrypted information is decrypted, the data is encrypted. Key codes of the encrypted key function table 31
(Kl, K2,..., Kn) are sequentially scanned to decrypt the encrypted information on the information recording medium 1, and the encryption key (K) read from the descramble data (RD) is read.
1 ') and the encryption key (Kl) set at the time of scanning by the encryption key collation circuit 38, and when they match, it is determined that the information including the encryption key recorded is correct. is there. Hereinafter, the operation of the embodiment shown in FIG. 1 will be described in detail for each of data encryption and decryption.

In order to generate encrypted scrambled data (S'WD) from non-scrambled data (WD) and record it on the information recording medium 1, the time data when the information recording medium 1 is accessed is obtained. New encrypted information is generated using the data and / or the number of accesses as parameters. In particular,
As an example of time data, 00 to 5 of access time
Depending on the frequency of use of the information recording medium 1 in the system, for example, 60 encryption keys are prepared for 9 minutes, or 24 encryption keys are prepared for 00 to 23:00. The number of encryption keys is determined by adjusting the length of seconds and the like. Also, in the case of the number of accesses, the number of encryption keys can be determined based on the number of digits. Further, by combining the two, the number of encryption keys may be determined based on, for example, the number of tens place and the number of minutes of time of the number of accesses.
In either case, it is possible to minimize the chance of selecting an encryption key at random and selecting the same encryption key continuously. First, the time data when the information recording medium 1 is accessed from the plurality of encryption keys (K1, K2,..., Kn) of the encryption key function table 31.
Data (Dc) and / or the number of accesses (Da) using one encryption key (Kl) selected together with the time data (Dc), the number of accesses (Da) and other data (Dn). At the same time, scramble data (WD) is formed and written into the data buffer 32, and at the same time, the scramble control unit 33 is set to an operable state. Next, the key code function Fs (K) of the encrypted key code function table 31 is set.
1, K2,..., Kn)
When the scramble parameter is written to the scramble control unit 33 by the key code function Fs (Kl) corresponding to 1), the scramble control unit 33 outputs the data arithmetic value processing circuit 3
4, the data digit processing circuit 35 and the data block processing circuit 36 are sequentially controlled to control the non-scrambled data (W
D) A predetermined scramble is applied to the arithmetic value, the digit, and the block to perform encryption, and scramble data (S'W)
D) is generated, and the reader / writer 2 is controlled by the scramble end signal from the scramble control unit 33 and recorded on the information recording medium 1.

In order to read out the scrambled data (S'WD) recorded on the information recording medium 1 and to decrypt the descrambled data (RD), first, the reader / writer 2 Encryption key by descramble start signal
A plurality of encryption keys (K1, K
2, ..., Kn) to scan one encryption key (K
1) to set the descrambling control unit 37 to an operable state. Next, the encryption key code function table 31
The key code function F corresponding to the encryption key (Kl) selected from the key code function Fd (K1, K2,..., Kn)
When the descrambling parameter is written into the descrambling control unit 37 by selecting d (Kl), the descrambling control unit 37 communicates with the data block processing circuit 36.
The digitizing and arithmetic values are read out by descrambling the block, digit and arithmetic value of the scrambled data (S'RD) block by sequentially controlling the digitizing circuit 35 and the arithmetic value processing circuit 34 to decode the data. Data (RD) is inversely generated and written into the data buffer 32,
The encryption key (Kl ') read from the output signal of the data buffer 32 is sent to the encryption key collation circuit 38 and collated with the fixed encryption key (Kl). This series of operations is sequentially performed on a plurality of encryption keys (K1, K2,
.., Kn) are scanned and executed. When the collation results match, the recording information of the information recording medium 1 by the encryption key is determined to be correct, and all the encryption keys (K1, K2,.
If the matching result does not match even after scanning n), the information is determined to be incorrect. When the verify check of the scrambled data (S'WD) recorded on the information recording medium 1 is performed, all the remaining descrambled data (RD) are unsynchronized when the above-mentioned encrypted key collation result matches. What is necessary is just to collate with the scramble data (WD) and confirm the coincidence.

[0013]

The present invention relates to a method for encrypting and decrypting an information recording medium, wherein each time an information recording medium is accessed, the encryption key is updated and new information is encrypted. However, it is possible to make it extremely difficult to decipher the encryption key by eavesdropping, so that the confidentiality of the encrypted information can be further enhanced, and compared with the conventional encryption key fixed encryption and decryption methods. And the confidentiality effect is great.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an information recording medium encryption method according to the present invention.

FIG. 2 is a block diagram illustrating an example of a conventional information recording medium encryption method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Information recording medium, 2 ... Leader-writer, 3 ... Scrambler / descrambler, 31 ... Encryption key function table, 32 ... Data buffer, 33 ... Scramble controller, 34 ... Data arithmetic value processing circuit, 35 ... Data digit processing circuit, 36 ... Data block processing circuit, 37 ...
Descrambling control unit, 38 ... encryption key matching circuit, 3
9: fixed encryption key code function table,

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H04L 9/10 H04L 9/00 621A

Claims (4)

[Claims] In an encryption method for recording predetermined information using an encryption key and encrypted information obtained by encrypting the encrypted key on an information recording medium, the information recording medium is accessed. One new encryption key is obtained from a plurality of encryption keys determined in advance, using data obtained at times as parameters.
Is selected and replaced with the encryption key to update the recording content of the information recording medium with new encryption information obtained by encrypting the predetermined information and the new encryption key. An information recording medium encryption method. 2. The method for encrypting an information recording medium according to claim 1, wherein the time data obtained when the information recording medium is accessed is used as a parameter. 3. The method according to claim 1, wherein the number of accesses obtained when accessing the information recording medium is a parameter. 4. An information recording medium decrypting method for reading out predetermined information and encrypted information obtained by encrypting the encrypted key from the information recording medium by using an encryption key, the method comprising: Encryption keys are selected one by one from the encryption keys, and the encryption information recorded on the information recording medium is sequentially decrypted, and the set encryption key and the decrypted encryption key are selected. A decryption method for an information recording medium, wherein the encrypted information can be read out when-is matched.