KR19990046658A - Chaos stream ciphering method for magnetic card - Google Patents

Abstract

The present invention relates to a method of encrypting a magnetic card Chaos Stream. The present invention relates to a magnetic card processing system having a magnetic card as a recording mother, wherein a magnetic code of a cryptographic code and a PN signal (encryption key) generated by using a chaos stream cipher is magnetically recorded and recorded on a magnetic card (encryption key). Using a method of restoring the encryption code using a combination of the PN signal (encryption key) prior to the restoration and restoring the encryption code.

Description

Magnetic card chaos stream encryption method {CHAOS STREAM CIPHERING METHOD FOR MAGNETIC CARD}

The present invention relates to a method of encrypting a magnetic card Chaos Stream.

The portable magnetic card is only 72 bytes per lane, but is widely used as an inexpensive storage matrix. It is easy to read or write using a card reader / writer. By supporting PC, magnetic card service using communication is possible, and it is a useful resource that can be used repeatedly.

If the stored information is used as money data, it becomes electronic money. Such electronic money is said to be more convenient than banknotes because it can simplify the processing of change. If you remember your personal information, it becomes your ID card. The magnetic card, which is a combination of these financial data and personal data, has become a factor in supporting today's consumer society by adding services.

It is a well-known fact that magnetic cards that store digitized information in one-to-one codes are weak to negation. When iron is applied to the magnetic card, the density of the lines of the magnetic card is visualized so that the digital code can be read even without a card reader. When the digital code corresponds to the ASCII code one-to-one, the contents of the information can be easily identified. In this sense, there is a tendency to give up that the prevention of self-memory is impossible.

In this way, copying the magnetic card can be performed simply. This copy of the magnetic card is easy to operate again making multiple copies.

Therefore, the present invention employs a chaos stream cipher that can be reproduced by calculation, so that only one copy is valid and the contents are encrypted, and thus the contents can not be decrypted even if the contents are copied. It is an object of the present invention to provide a card chaos stream encryption method.

According to the magnetic card chaos stream encryption method of the present invention for achieving the above object, chaos and the like to correct the contents of the magnetic card or to illegally access information such as mischief, and to correctly preserve digital information without error of 1 bit. Stream ciphers were used. In the conventional way, it was easy to make a copy of a magnetic card. For example, copying a line as it is, even if it is coded, creates multiple or multiple duplicate cards that record the same information. However, the present invention effectively treats only one of multiple duplicate cards as a valid card, thereby illegally accessing the remaining cards. prevent.

1 is a block diagram of a magnetic card according to the present invention.

<Description of the symbols for the main parts of the drawings>

1 ------------- Magnetic Card 2 ------------- Magnetic Stripe

3 ------------- PN Signal (Encryption Key) 4 -------------- Encryption Code

Hereinafter, an embodiment of the present invention will be described in detail.

The chaos stream cipher consists of an encryption key, an encryption table, and a retrieval table. The principle of this encryption method is the logistic map of chaos x (t + 1) = 4x (t) {1-x (t)}, feedback x (t) = x (t + 1), in-phase transformation y (t) = PN (Pseudo Noise) is used for the binary code sequence cut out from the binary code time series y (t) -t obtained as n = 1 in [{2 / ∏ · arcsin √x (t)} · 2]. It is used as a signal. Where [] means a truncation operation below the decimal point and t is the dispersion time t = 0,1,2, ..

The storage capacity of one magnetic card is usually 72 bytes. If 36 bytes are cipher key = PN signal, the length of binary code is 36 bytes = 288 bits. y (0) to y (287) are the PN signals 1, and y (288) to y (575) are the PN signals 2. Correspondingly, the encryption code (the length of the document to be encrypted) is also 36 bytes = 288 bits. The encryption code can be changed by performing an EXOR operation between 36 bytes of the document to be encrypted and 36 bytes of the PN signal.

Likewise, for simple encryption to be effective, the time series y (t) -t, which can be obtained by calculating the logistic map, must be "0" and "1" as if it were a random number that can be obtained by tossing coins fairly. There is. Self-correlation and cross-correlation of the broken binary code sequence must be thoroughly verified.

The computational speed of the logistic map is calculated on a digital computer, so the computational accuracy of the computer (double 64-bit) is important. If the initial value x (0) is defined by 52 bits of mantissa, it is possible to utilize a time series y (t) -t such as 2 = 4.50 × 10. It can be said that the kind of PN signal (encryption key) that can be prepared is infinite in industrial technology.

Chaos is said to contain an infinite cycle. The time series y (t) -t of the binary code sequence, which can be obtained by computing computer-reproducible industrial techniques or logistic maps, follows a probability distribution that can be called a random sequence or a noise sequence. As a result, the following fraudulent access protection for the magnetic card is brought.

(1) The 36-byte encryption code is a distribution of binary codes that are sufficiently spread, and the encryption key (PN signal) recorded at the same time cannot be correctly restored even if the 1 bit is different. Therefore, fixing or physically joking (scratching, folding, folding, etc.) makes the recording difficult and invalidates the card.

(2) In the magnetic card system, the server manages issuance of as many PN signals as necessary using a PC as a server. Therefore, the restoration process is performed by combining the encryption keys, that is, the PN signals. Magnetic cards are easy to copy and free, but only one card can be used properly. That is, it does not allow unauthorized copying.

(3) In issuance of magnetic cards, it is possible to collect personal information in various forms. Another method is to set a personal identification number (ID number). If it is a four-digit password, four bytes are required. If personal information is available for identification, for example, in the case of electronic money, the information to be encrypted and stored in the magnetic card is the balance amount and the ID number. If you prepare a management system on the PC server side to combine ID numbers, you can prevent others from using your lost magnetic cards.

(4) A magnetic card unauthorized access prevention system that executes a combination of an encryption key (PN signal) and an ID number on the PC server side guarantees the reissue of a lost card as a consequent result.

(Example)

The encryption process of the present invention is shown in FIG. This is the case when the magnetic stripe 1 has one magnetic stripe 2. Typically, 72 bytes of storage are allocated. 36 bytes 3 are allocated to the PN signal (encryption key) 36 bytes and 36 bytes 4 are assigned to the encryption code. You can remember 36 ASCII code characters.

The 72 bytes of storage need not be divided one-to-one into encryption key 3 and encryption key 4. When the encryption key is shortened and the encryption code is made long, the EXN exclusive logical operation may be executed by turning the PN signal in a binary sequence. This is the so-called stream cipher.

For example, when information to be encrypted is 6 bytes of ID number, 6 bytes of balance amount, and 12 bytes in total, 36 bytes of PN signals may be spread three times to perform the EXOR operation. It is a so-called spectle diffusion method. When spreading, error checking is automatically performed during restoration. Password robustness is improved.

Binary data, PN signal and encryption code, which should be recorded on magnetic card at PN server side, are prepared and verified, and basic operation (inverted, rotated, inverted) is applied when data is transferred to magnetic card writer. This is done. The reverse operation is applied when reading the magnetic card data with the magnetic card reader.

The length of the PC signal is not limited and the processing speed is 10MB / S (CPU clock 300MHz), and the PN signal can be cycled to make the stream cipher asynchronous.

As described above, the chaos stream encryption method is useful for preventing unauthorized access to an electronic key, preventing unauthorized access to documents and data in a memory of a PC, in addition to preventing unauthorized access to a magnetic card. The magnetic card system is a specific example of the anti-fraud technology in close proximity to the civil life that uses a combination of encryption keys and ID numbers (personal information) through small and short communication. Whether it is effective to prevent inadvertent access of large corporate systems such as telephones, banks and railways depends on the reduction of communication costs.

Accident and safety measures must be considered in preventing unauthorized access to magnetic cards. Another method is to input in the reverse direction by using a plurality of magnetic stripes.

The development of industrial general purpose CPUs and memories is remarkable. If the display by the CRT is not required, it is also effective to install a program and a database (PN signal) in the magnetic card reader / writer.

In this example, a simple example of calculating a PN signal (encryption key) by chaos is shown. However, it is also possible to perform stream encryption restoration while generating a PN signal in an integrated circuit using a nonlinear mapping circuit and an AD conversion. When using a PC server for user management, such as a magnetic card fraud prevention system, it is better to rely on calculations as in this proposal. Since the inverse problem of decryption cannot be set, integrated circuitry can increase the robustness of the encryption.

Claims (1)

In a magnetic card processing system using a magnetic card as a recording mother, a magnetic code of a cryptographic code and a PN signal (encryption key) generated by using a chaos stream cipher is magnetically recorded and a PN signal (encryption key) recorded on the magnetic card is used. A method of restoring an encryption code and a combination of a PN signal (encryption key) prior to the restoration, and restoring the encryption code.