JP2009230807A - Magnetic recording apparatus and magnetic recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording apparatus and a magnetic recording method improving security by recording encrypted data. <P>SOLUTION: The magnetic recording apparatus has: magnetic wires 12a to 12p that include a magnetic material and record data by a magnetization direction in magnetic domains which correspond to a minimum unit of the data, a magnetic domain driving section 14 that moves the magnetic domains by applying a current to the magnetic wires 12a to 12p, an encrypting section 86 that encrypts input data, writing sections 18a to 18p that write the encrypted data encrypted at the encrypting section 86 in the magnetic domains of the magnetic wires 12a to 12p, reading sections 16a to 16p that read the encrypted data written by the writing sections 18a to 18p from the magnetic domains of the magnetic wires 12a to 12p, and a decoding section 84 that decodes and outputs the encrypted data which is read from the magnetic domains of the magnetic wires 12a to 12p by the reading sections 16a to 16p. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic recording apparatus and a magnetic recording method, and more particularly to a magnetic recording apparatus and a magnetic recording method that include a magnetic material and record data according to a magnetization direction inside a magnetic domain.

  Recently, as a new memory system, a domain wall moving storage memory using a domain wall current drive phenomenon (see Non-Patent Document 1) by a spin torque transfer effect has been proposed (see Patent Document 2).

  A magnetic domain is formed in the magnetic material so that the magnetostatic energy is minimized, and a domain wall is formed at the boundary of the magnetic domain. When the magnetic material thin film is formed into a fine line by fine processing such as a semiconductor manufacturing technique, the magnetization difficult direction and the easy magnetization direction are controlled by the shape, so that a single magnetic domain is formed in the width direction of the thin line. This fine wire is called a magnetic fine wire. When a pulse current is applied to the magnetic wire, when the conduction electron crosses the domain wall, the spin of the conduction electron rotates along the magnetic moment by the sd interaction. At this time, the spin angular momentum of the conduction electrons is absorbed into the magnetic moment by the conservation of angular momentum. As a result, the magnetic moment rotates and the domain wall moves. That is, the domain wall and the magnetic domain can be moved by the spin torque transfer effect. Therefore, if the writing of the magnetization direction to the magnetic domain of the magnetic wire and the reading of the magnetization direction from the magnetic domain of the magnetic wire can be performed, the magnetic wire can function as a memory.

The domain wall motion storage memory is capable of recording a large number of data with respect to a single magnetic wire, so that it is easy to improve the recording density and is expected as a new large-capacity memory.
Physical Review Letters V92, Number. 7 077720-1 JP 2006-237183 A Research Trend of Spin Injection Magnetization Reversal, Japan Society of Applied Magnetics Vol. No. 28 9,2004

  For the domain wall motion storage memory, it is necessary to protect the recorded data from security requirements. However, the conventional magnetic recording apparatus can easily analyze the recording data by measuring the magnetization direction of the magnetic domain using, for example, a magnetic force microscope. For this reason, it is necessary to take measures against information leakage.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a magnetic recording apparatus and a magnetic recording method with improved security by encrypting and recording data.

  The magnetic recording device disclosed in the specification of the present application includes a magnetic material, and records data according to the magnetization direction inside the magnetic domain. The magnetic domain is a magnetic wire corresponding to the minimum unit of the data, and a current is supplied to the magnetic wire. A magnetic domain drive unit that moves the magnetic domain by applying a magnetic field; an encryption unit that encrypts the input data; and encrypted data that is the data encrypted by the encryption unit. A writing unit for writing to the magnetic domain, a reading unit for reading the encrypted data written by the writing unit from the magnetic domain of the magnetic wire, and the cipher read from the magnetic domain of the magnetic wire by the reading unit And a decrypting unit that decrypts the encoded data and outputs the decrypted data.

  The magnetic recording method disclosed in the specification of the present application includes a magnetic material, and records data according to the magnetization direction inside the magnetic domain, and the magnetic domain records the data with respect to the magnetic wire corresponding to the minimum unit of the data. A magnetic recording method, the step of moving the magnetic domain by applying a current to the magnetic wire, the step of encrypting the input data, and the encryption being the encrypted data Writing data into the magnetic domain of the magnetic wire, reading the written encrypted data from the magnetic domain of the magnetic wire, and decrypting the encrypted data read from the magnetic domain of the magnetic wire. And a step of outputting the output.

  According to the magnetic recording apparatus and the magnetic recording method disclosed in the specification of the present application, data can be encrypted and recorded. Therefore, it is effective in improving security.

  For comparison with the embodiment of the present invention, an example of a magnetic recording apparatus using a domain wall motion storage memory will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of a magnetic recording apparatus using a domain wall motion storage memory. In FIG. 1, the magnetic recording device is connected to an external device such as a CPU (Central Processing Unit), receives data from the external device, writes data to the magnetic recording device, and from the magnetic recording device. The data is read out.

  The magnetic recording apparatus 10 includes a magnetic wire 12, a magnetic domain driving unit 14, a reading unit 16, a writing unit 18, a writing signal processing unit 20, a reading signal processing unit 22, a system controller 24, and a ground terminal 26. Have.

  In response to a write request from an external device, the magnetic recording device 10 writes data to the magnetic domain 70 of the magnetic wire 12. The magnetic recording device 10 reads data from the magnetic domain 70 of the magnetic wire 12 in response to a read request from an external device.

  The system controller 24 controls the entire system of the magnetic recording apparatus 10. The system controller 24 includes a read control unit 58, a write control unit 60, and a magnetic domain drive control unit 62. The read control unit 58 controls the magnetic domain drive control unit 62 via the magnetic domain drive control unit control signal line 74. The write control unit 60 controls the magnetic domain drive control unit 62 via the magnetic domain drive control unit control signal line 72.

  The magnetic wire 12 includes a first storage unit 64, a second storage unit 66, and a data area unit 68 sandwiched between the first storage unit 64 and the second storage unit 66. The data area portion 68 has a plurality of magnetic domains 70. One end of the magnetic wire 12 is connected to the ground terminal 26, and the other is connected to the magnetic domain driving unit 14. Each magnetic domain 70 of the magnetic wire 12 corresponds to 1-bit data which is the minimum unit. A value designating one of the plurality of magnetic domains 70 of the magnetic thin wire 12 corresponds to the data address. The line width of the magnetic wire is preferably 500 nm or less so that a single magnetic domain is formed in the width direction of the magnetic wire.

  The write control unit 60 instructs the write signal processing unit 20 and the magnetic domain drive control unit 62 to control the entire data writing process.

  The read control unit 58 instructs the read signal processing unit 22 and the magnetic domain drive control unit 62 to control the entire data read processing.

  The read signal processing unit 22 includes a comparator circuit and a reference voltage element. The read signal processing unit 22 compares the voltage read by the read unit 16 with the voltage of the reference voltage element in the read signal processing unit 22 via the data signal line 54 by using a comparator circuit, and the binary information of either large or small Is output to the data signal line 50. The reading unit 16 uses, for example, a TMR element (tunnel magnetoresistive element).

  The write signal processing unit 20 instructs the write unit 18 to write via the write unit control signal line 42. The write signal processing unit 20 generates a pulse current for changing the magnetization direction of the magnetic domain 70 of the magnetic wire 12 by a spin injection magnetization reversal method (see Non-Patent Document 3). The write signal processing unit 20 applies a pulse current to the write unit 18 via the data signal line 56. For example, a TMR element (tunnel magnetoresistive element) is used for the writing unit 18.

  The magnetic domain drive control unit 62 instructs the magnetic domain drive unit 14 to apply a pulse current to the magnetic wire 12 via the magnetic domain drive unit control signal line 48. The magnetic domain drive unit 14 applies a pulse current to the magnetic thin wire 12 via the pulse current application line 44. Thereby, the magnetic domain 70 of the magnetic wire 12 moves.

  A procedure for writing data to the magnetic recording apparatus 10 will be described with reference to FIG.

  The write control unit 60 receives a write instruction from an external device via the write request signal line 30.

  The write control unit 60 receives data input from an external device. At this time, the write controller 60 is notified of data from the external device via the data signal line 34. The write controller 60 is notified of the data address from the external device via the address signal line 32.

  The write control unit 60 instructs the magnetic domain drive control unit 62 to move the magnetic domain 70 of the magnetic wire 12 via the magnetic domain drive control unit control signal line 72. The magnetic domain drive control unit 62 instructs the magnetic domain drive unit 14 to apply a pulse current to the magnetic thin wire 12 via the magnetic domain drive unit control signal line 48. The magnetic domain drive unit 14 applies a pulse current to the magnetic thin wire 12 via the pulse current application line 44. Thereby, the magnetic domain 70 of the magnetic wire 12 moves.

  The write control unit 60 instructs the write signal processing unit 20 to write via the write signal processing unit control signal line 38. The write control unit 60 notifies the write signal processing unit 20 of data via the data signal line 52.

  The write signal processing unit 20 generates a pulse current for changing the magnetization direction of the magnetic domain 70 of the magnetic wire 12 by a spin injection magnetization reversal method (see Non-Patent Document 3). The write signal processing unit 20 instructs the write unit 18 to write via the write unit control signal line 42. The write signal processing unit 20 applies a pulse current to the write unit 18 via the data signal line 56. The writing unit 18 writes data to the magnetic domain 70 of the magnetic wire 12 corresponding to the designated address.

  Thus, writing of data to the magnetic recording device 10 is completed.

  Next, a procedure for reading data from the magnetic recording apparatus 10 will be described with reference to FIG.

  The magnetic recording device 10 receives an instruction to read data from an external device. At this time, the read control unit 58 receives a read instruction from the external device via the read request signal line 28. The read control unit 58 is notified of the data address from the external device via the address signal line 32.

  The read control unit 58 instructs the magnetic domain drive control unit 62 to move the magnetic domain 70 of the magnetic wire 12 via the magnetic domain drive control unit control signal line 74. The magnetic domain drive control unit 62 instructs the magnetic domain drive unit 14 to apply a pulse current to the magnetic thin wire 12 via the magnetic domain drive unit control signal line 48. The magnetic domain drive unit 14 applies a pulse current to the magnetic thin wire 12 via the pulse current application line 44. Thereby, the magnetic domain 70 of the magnetic wire 12 moves.

  The read control unit 58 instructs the read signal processing unit 22 to read via the read signal processing unit control signal line 36. The read signal processing unit 22 initializes an internal comparator circuit.

  The read signal processing unit 22 instructs the read unit 16 to read via the read unit control signal line 40. The reading unit 16 reads data from the magnetic domain 70 of the magnetic wire 12 corresponding to the specified address. The read data is notified to the read signal processing unit 22 via the data signal line 54, and the comparator circuit inside the read signal processing unit 22 performs a magnitude comparison process with the reference voltage. At this time, the read data is determined. The determined data is notified to the read control unit 58 via the data signal line 50 and is notified to the external device via the data signal line 34.

  Thus, reading of data from the magnetic recording device 10 is completed.

  As described above, the magnetic recording apparatus 10 does not include means for protecting data recorded in the magnetic domain 70 of the magnetic wire 12. Therefore, it is easy to analyze the data recorded in the magnetic recording apparatus 10 by measuring the magnetization direction of the magnetic domain 70. For this reason, it is necessary to take measures against information leakage. Examples 1 and 2 of the present invention that solve the above-described problems will be described below.

  Example 1 of the present invention will be described below.

  FIG. 2 is a block diagram illustrating the configuration of the magnetic recording apparatus according to the first embodiment. In FIG. 2, the magnetic recording device is connected to an external device such as a CPU (Central Processing Unit) and receives data from the external device and writes data and reads data. 2 are the same as those in FIG. 1, the description thereof is omitted.

  The magnetic recording device 80 includes 16 magnetic thin wires 12a to 12p, a magnetic domain drive unit 14, a write signal processing unit 20, a read signal processing unit 22, a system controller 82, and a ground terminal 26. In addition, an encryption unit 86 and a decryption unit 84 are included. Moreover, it has the read-out parts 16a-16p and the write-in parts 18a-18p corresponding to the magnetic fine wires 12a-12p, respectively. In FIG. 2, 12a, 12b, and 12p are illustrated about the magnetic wires 12a-12p. Moreover, 16a, 16b, 16p is illustrated about the reading parts 16a-16p. For the writing units 18a to 18p, 18a, 18b, and 18p are illustrated.

  The magnetic thin wires 12a to 12p are arranged adjacent to each other in parallel. Data recorded on each of the magnetic thin wires 12a to 12p has a matrix structure having a plurality of rows and a plurality of columns. Each row corresponds to each magnetic wire 12a-12p. Each column corresponds to each data written at a time to each magnetic wire 12a-12p or each data read at a time from each magnetic wire 12a-12p. Here, the magnetic fine wire corresponding to the most significant digit of the data recorded in each column is designated as 12a, and the magnetic fine wires corresponding to the subsequent digits are designated as 12b, 12c,. Is 12p. Each magnetic domain 70 of each magnetic wire 12a-12p corresponds to 1-bit data which is the minimum unit. A combination of a row number specifying a row and a column number specifying a column corresponds to the address of the data.

  In response to a write request from an external device, the magnetic recording device 80 writes data to each magnetic domain 70 of each magnetic wire 12a-12p. In response to a read request from an external device, the magnetic recording device 80 reads data from each magnetic domain 70 of each magnetic wire 12a-12p.

  The system controller 82 controls the entire system of the magnetic recording device 80, and includes a read control unit 58, a write control unit 60, a magnetic domain drive control unit 62, an encryption control unit 100, and a decryption control unit 102. including. The read control unit 58 controls the magnetic domain drive control unit 62 via the magnetic domain drive control unit control signal line 74. The write control unit 60 controls the magnetic domain drive control unit 62 via the magnetic domain drive control unit control signal line 72.

  The magnetic wires 12a to 12p are respectively sandwiched between the first storage units 64a to 64p, the second storage units 66a to 66p, the first storage units 64a to 64p, and the second storage units 66a to 66p. Data area portions 68a to 68p. Each data region portion 68 a to 68 p has a plurality of magnetic domains 70. One end of each of the magnetic thin wires 12 a to 12 p is connected to the ground terminal 26, and the other is connected to the magnetic domain driving unit 14.

  The encryption control unit 100 controls the encryption unit 86 via the encryption unit control signal line 94. The decoding control unit 102 controls the decoding unit 84 via the decoding unit control signal line 88.

  A procedure for writing data to the magnetic recording apparatus 80 according to the first embodiment will be described with reference to FIGS. 2, 3, and 4 (a) and 4 (b).

  FIG. 3 shows a flowchart of processing for writing data to the magnetic recording device 80. 4A and 4B show recording states of data written in the magnetic domains 70 of the magnetic thin wires 12a to 12p in FIG. 4A and 4B show a state in which the magnetic thin wires 12a to 12p in FIG. 2 are arranged in a horizontal direction from top to bottom. Each row corresponds to each magnetic wire. Each square corresponds to each magnetic domain 70.

  The write control unit 60 receives a write instruction from an external device via the write request signal line 30. (Step S110)

  The write control unit 60 receives data input from an external device. (Step S112) At this time, the write controller 60 is notified of data from an external device via the data signal line. The write controller 60 is notified of the data address from the external device via the address signal line 32. The write control unit 60 notifies the notified data to the encryption unit 86 via the data signal line 96.

  The encryption control unit 100 instructs the encryption unit 86 to encrypt the data notified to the encryption unit 86 via the encryption unit control signal line 94. The encryption unit 86 encrypts data. (Step S192)

  The write control unit 60 instructs the magnetic domain drive control unit 62 to move the magnetic domains 70 of the magnetic thin wires 12a to 12p via the magnetic domain drive control unit control signal line 72. The magnetic domain drive control unit 62 instructs the magnetic domain drive unit 14 to apply a pulse current to each of the magnetic thin wires 12a to 12p via the magnetic domain drive unit control signal line 48. The magnetic domain drive unit 14 applies a pulse current to the magnetic thin wires 12a to 12p via the pulse current application lines 44a to 44p. Thereby, each magnetic domain 70 of each magnetic wire 12a-12p moves. The write control unit 60 instructs the write signal processing unit 20 to write via the write signal processing unit control signal line 38. The write signal processing unit 20 generates a pulse current for changing the magnetization direction of each magnetic domain 70 of each of the magnetic wires 12a to 12p by a spin injection magnetization reversal method (see Non-Patent Document 3). The write signal processing unit 20 instructs the write units 18a to 18p to write via the write unit control signal lines 42a to 42p. The write signal processing unit 20 applies a pulse current to the write units 18a to 18p via the data signal lines 56a to 56p. Each writing part 18a-18p writes data with respect to each magnetic domain 70 of each magnetic wire 12a-12p corresponding to the designated address. (Step S118)

  FIG. 4A shows an example of a recording state of data written in the magnetic domains 70 of the magnetic thin wires 12a to 12p when step S118 is completed. This indicates that data is recorded in a column 180 indicated by shading.

  In step S118, after all the data has been written to the magnetic domains 70 of the magnetic thin wires 12a to 12p corresponding to the designated address, some of the magnetic thin wires are moved. Here, as an example, a case where each magnetic domain 70 of the magnetic thin wires 12i and 12o is moved to the left by one bit is shown. The write control unit 60 instructs the magnetic domain drive control unit 62 to move the magnetic domains 70 of the magnetic thin wires 12i and 12o via the magnetic domain drive control unit control signal line 72. The magnetic domain drive control unit 62 instructs the magnetic domain drive unit 14 to apply a pulse current to the magnetic thin wires 12 i and 12 o via the magnetic domain drive unit control signal line 48. The magnetic domain drive unit 14 applies a pulse current to the magnetic thin wires 12i and 12o via the pulse current application lines 44i and 44o. As a result, the magnetic domains 70 of the magnetic wires 12i and 12o move. (Step S196)

  FIG. 4B shows an example of a recording state of data written on the magnetic thin wires 12a to 12p when step S196 is completed. Here, the case where each magnetic domain 70 of the magnetic thin wires 12i and 12o described above is moved to the left by one bit is shown.

  Thus, the data writing to the magnetic recording device 80 is completed.

  The details of the data encryption process performed by the encryption unit 86 in step S192 shown in the flowchart of FIG. 3 will be described in more detail with a specific example.

Here, an RSA (Rivest, Shamir and Adleman) encryption method is used as an example of a data encryption method. In the RSA encryption method, an appropriate positive integer e is selected and two prime numbers {p, q} are generated and used as keys (secret keys) used for decrypting ciphertext. Next, a product n of the two prime numbers generated is obtained, and {e, n} is used as a key (public key) used for plaintext encryption. If the plaintext is A and the ciphertext encrypted with the public key {e, n} is RsaA, RsaA is calculated as follows.
RsaA = mod (A ^ e, n)

  In the encryption process, first, three parameters for RSA encryption are determined. Here, n, which is a product of prime numbers p = 11 and q = 17, is n. In addition, e is 3 as a value such that the greatest common divisor of (p−1) × (q−1) is 1. In addition, 107 is set to d as a value such that a remainder obtained by dividing the product of e by (p−1) × (q−1) is 1.

Here, if the plaintext input to the magnetic recording device 80 is A = 7 and A is encrypted with the public key {e, n} = {3,187}, the ciphertext RsaA is calculated as follows.
RsaA = mod (7 ^ 3,187) = 156
The above is an example of the process performed by the encryption unit 86 in step S192.

  A procedure for reading data from the magnetic recording apparatus 80 according to the first embodiment will be described with reference to FIGS. 2, 4 (a), 4 (b), and 5.

  FIG. 5 shows a flowchart of processing for reading data from the magnetic recording device 80.

  The read control unit 58 receives a read instruction from the external device via the read request signal line 28. (Step S122) At this time, the read control unit 58 is notified of the address of the data from the external device via the address signal line 32.

  Next, some of the magnetic wires are moved. Here, as an example, a case where the magnetic domains 70 of the magnetic thin wires 12i and 12o are moved to the right by 1 bit is shown. The read controller 58 moves the magnetic wires 12i and 12o among the magnetic wires 12a to 12p, and therefore the magnetic wires 12i and 12o are transferred to the magnetic domain drive controller 62 via the magnetic domain drive controller control signal line 74. The movement of each magnetic domain 70 is instructed. The magnetic domain drive control unit 62 instructs the magnetic domain drive unit 14 to apply a pulse current to the magnetic thin wires 12 i and 12 o via the magnetic domain drive unit control signal line 48. The magnetic domain drive unit 14 applies a pulse current to the magnetic thin wires 12i and 12o via the pulse current application lines 44i and 44o. As a result, the magnetic domains 70 of the magnetic wires 12i and 12o move. (Step S200)

  An example of the process of step S200 will be described with reference to FIGS. In step S200, the magnetic domains 70 of the magnetic wires 12i and 12o are shifted to the left by 1 bit as shown in FIG. 4B, and the magnetic domains 70 of the magnetic wires 12i and 12o are changed as shown in FIG. The magnetic domains 70 of the magnetic fine wires 12i and 12o are moved so as not to be shifted.

  The read control unit 58 instructs the magnetic domain drive control unit 62 to move the magnetic domains 70 of the magnetic thin wires 12a to 12p via the magnetic domain drive control unit control signal line 74. The magnetic domain drive control unit 62 instructs the magnetic domain drive unit 14 to apply a pulse current to each of the magnetic thin wires 12a to 12p via the magnetic domain drive unit control signal line 48. The magnetic domain drive unit 14 applies a pulse current to the magnetic thin wires 12a to 12p via the pulse current application lines 44a to 44p. Thereby, each magnetic domain 70 of each magnetic wire 12a-12p moves. The read control unit 58 instructs the read signal processing unit 22 to read via the read signal processing unit control signal line 36. The read signal processing unit 22 initializes the comparator circuit. The read signal processing unit 22 instructs the read units 16a to 16p to read via the read unit control signal line 40. Each reading part 16a-16p reads data from each magnetic domain 70 of each magnetic wire 12a-12p corresponding to the designated address. The read data is notified to the read signal processing unit 22 via the data signal lines 54a to 54p, and the comparator circuit inside the read signal processing unit 22 performs a magnitude comparison process with the reference voltage. At this time, the read data is determined. The determined data is notified to the decoding unit 84 via the data signal line 92. (Step S124)

  The decoding control unit 102 instructs the decoding unit 84 to decode data via the decoding unit control signal line 88. The decrypting unit 84 decrypts data. The decryption unit 84 notifies the read control unit 58 of the data that has been decrypted via the data signal line 90. (Step S204)

  The read control unit 58 outputs the notified data to the external device via the data signal line 34. (Step S130)

  Thus, reading of data from the magnetic recording device 80 is completed.

  In step S204 shown in the flowchart of FIG. 5, the details of the data decoding process performed by the decoding unit 84 will be described in more detail with a specific example. Here, as an example of step S204, similarly to the example of step S192 of the flowchart of FIG. 3 described above, the values of plaintext, ciphertext, and key are the same as the values described above using the RSA encryption method. Identical.

In response to an instruction from the decoding control unit 102 of the system controller 82, the decoding unit 84 performs data decoding. In the RSA encryption method, the ciphertext RsaA is decrypted into plaintext A by the following formula.
A = mod (RsaA ^ d, n)
Here, since RsaA = 156, d = 107, and n = 187, plaintext A is calculated as follows.
A = mod (156 ^ 107,187) = 7
The decrypted A is notified from the decryption unit 84 to the read control unit 58. The above is an example of the process performed by the decoding unit 84 in step S204.

  In the magnetic recording apparatus according to the first embodiment, after the writing unit writes the encrypted data, the magnetic domain driving unit applies a current to the magnetic thin wires corresponding to some of the plurality of rows. The magnetic domain can be moved. Further, after the magnetic domain driving unit moves the magnetic domain by applying a current to the magnetic wires corresponding to some of the plurality of rows, the reading unit can read the encrypted data. it can. Since the number of combinations for selecting magnetic wires corresponding to some rows is 2 (the number of magnetic wires) to the power, data encryption can be strengthened, which is effective in improving security. There is.

  In the first embodiment, the magnetic domain driving unit moves the magnetic domains of the magnetic wires corresponding to some of the plurality of rows, which is an application of the operation of the magnetic domain driving unit in the magnetic recording apparatus. It does not require a complicated circuit. For this reason, it is possible to reduce the cost and improve the security.

  In Example 1, when a magnetic domain drive part moves a magnetic domain by applying an electric current with respect to the magnetic thin wire | line corresponding to some rows among several rows, each movement amount of some rows is the same The example of 1 bit is described. Accordingly, the amount of calculation can be suppressed while improving the security in the magnetic recording apparatus, which is effective in reducing the cost.

  In the first embodiment, an example in which the RSA encryption method is applied as the encryption method has been shown. However, for example, an arbitrary encryption method such as a DES (Data Encryption Standard) encryption method or an ElGamal encryption method may be applied. Good. Since any encryption method can be applied, it is effective in improving security.

  Example 2 of the present invention will be described below.

  A procedure for writing data to the magnetic recording apparatus 80 according to the second embodiment will be described with reference to FIGS. Explanation of the same steps as those in the first embodiment is omitted.

  FIG. 6 shows a flowchart for writing data to the magnetic recording device 80.

  First, step S110 and step S112 are the same as the flowchart of FIG.

  Next, the encryption control unit 100 instructs the encryption unit 86 to perform first encryption of the data notified to the encryption unit 86 via the encryption unit control signal line 94. The encryption unit 86 performs first encryption of data. (Step S114) Details of the first encryption processing will be described later.

  The encryption control unit 100 instructs the second encryption of the data notified to the encryption unit 86 via the encryption unit control signal line 94. The encryption unit 86 performs second encryption of data. (Step S116) Details of the second encryption process will be described later. The encryption unit 86 notifies the write signal processing unit 20 of the second encrypted data through the data signal line 98.

  Step S118 is the same as the flowchart of FIG.

  Thus, the data writing to the magnetic recording device 80 is completed.

  The details of processing performed by the encryption unit 86 in steps S114 and S116 shown in the flowchart of FIG. 6 will be described in more detail with reference to specific examples.

  FIGS. 8A and 8B show a state in which the magnetic fine wires 12a to 12p in FIG. 2 are arranged in a horizontal direction from top to bottom. Each row corresponds to each magnetic wire. Each square corresponds to each magnetic domain 70. FIG. 8A shows an example of a state in which data obtained by performing only the first encryption is recorded on the magnetic thin wires 12a to 12p. FIG. 8B shows an example of a state in which data subjected to the first encryption and the second encryption is recorded on the magnetic thin wires 12a to 12p.

  In step S114, the first encryption process performed by the encryption unit 86 is encrypted using the RSA encryption method as in the example of step S192 in the flowchart of FIG. 3 described above. Description is omitted. Hereinafter, the parameters to be described are also set to the same values as those in step S192 in the flowchart of FIG.

  FIG. 8A shows a state in which RsaA is recorded in a column 134 indicated by shading in the third column from the left.

The contents of the second encryption process performed by the encryption unit 86 in step S116 will be described. First, the write shift value Dsh is defined. For example, Dsh is a binary number having the maximum number of magnetic wires as the number of digits. When the value of a certain digit of Dsh is 1, the magnetic domain 70 corresponding to the digit is moved to the left by 1 bit. When the value of a digit of Dsh is 0, the magnetic domain 70 corresponding to that digit is not moved. In the magnetic recording apparatus 80 of FIG. 2, the number of digits of Dsh is 16 digits. Further, the most significant digit of Dsh corresponds to the magnetic fine wire 12a, the magnetic fine wires corresponding to the subsequent digits are sequentially designated as 12b, 12c,..., And the magnetic fine wire corresponding to the least significant digit is designated as 12p. For example, when the magnetic domains 70 of the magnetic thin wires 12i and 12o are moved to the left by 1 bit, the value of Dsh is as follows.
Dsh = 0000000000001000010 (130 in decimal)

  In the magnetic recording device 80, the value of Dsh is held in, for example, the write control unit 60, the read control unit 58, or the storage unit (not shown) of the system controller 82. For example, the value of Dsh may be held in each of the magnetic thin wires 12a to 12p, and is not particularly limited.

The second encryption process is a process of moving some rows of data using the Dsh. The second encryption process will be specifically described. The encryption unit 86
RsaA = RsaAs (0) || RsaAs (1)
The divided ciphertexts RsaAs (0) and RsaAs (1) that satisfy the logical operation expression are generated. RsaAs (0) and RsaAs (1) are values obtained by logically inverting RsaA, Dsh, and Dsh! (Dsh) and is calculated by the following equation.
RsaAs (0) = RsaA && Dsh
RsaAs (1) = RsaA &&! (Dsh)
For example,
RsaA = 156
In this case, RsaAs (0) and RsaAs (1) are as follows.
RsaAs (0) = 156 && 130 = 128
(When expressed in 16-bit binary numbers, it is 0000000010000000.)
RsaAs (1) = 156 && 65405 = 28
(When expressed in a 16-bit binary number, it is 00000000000011100.)

  FIG. 8B shows a state in which RsaAs (0) is recorded in the second column 136 from the left, and RsaAs (1) is recorded in the third column 138 from the left. Comparing FIG. 8A and FIG. 8B, it can be seen that the row corresponding to the magnetic thin wires 12i and 12o has moved to the left by one bit by the second encryption processing.

  The above is an example of the process of step S116.

  A procedure for reading data from the magnetic recording apparatus 80 according to the second embodiment will be described with reference to FIGS. Explanation of the same parts as those in the first embodiment is omitted.

  FIG. 7 shows a flowchart for reading data from the magnetic recording device 80.

  Steps S122 and S124 are the same as those in the flowchart of FIG.

  The decoding control unit 102 instructs the decoding unit 84 to first decode the data via the decoding unit control signal line 88. The decryption unit 84 performs first decryption of the data. (Step S126) Details of the first decoding process will be described later.

  The decoding control unit 102 instructs the decoding unit 84 to perform second decoding of data via the decoding unit control signal line 88. The decrypting unit 84 performs the second decryption of the data. (Step S128) Details of the second decoding process will be described later. The decoding unit 84 notifies the read control unit 58 of the data that has been subjected to the second decoding of the data, via the data signal line 90.

  Step S130 is the same as the flowchart of FIG.

  Thus, reading of data from the magnetic recording device 80 is completed.

  The processing contents performed by the decoding unit 84 in steps S126 and S128 shown in the flowchart of FIG. 7 will be described in more detail with a specific example. Here, as an example, a case where data shown in FIG. 8B is read will be described.

The contents of processing performed by the decoding unit 84 in step S126 will be described. RsaAs (0) and RsaAs (1) read in step S124 are notified to the decoding unit 84. The decryption unit 84 is a value obtained by logically inverting RsaAs (0), RsaAs (1), Dsh, and Dsh! (Dsh) is used to decode RsaA, which is the value before moving the magnetic domain 70 left by 1 bit. Here, RsaA is decoded by the following logical operation expression.
RsaA (0) = RsaAs (0) && Dsh
RsaA (1) = RsaAs (1) &&! (Dsh)
RsaA = RsaA (0) || RsaA (1)
Here, it is calculated as follows.
RsaA (0) = 128 && 130 = 128
RsaA (1) = 28 && 65405 = 28
RsaA = 128 || 28 = 156
The above is an example of the process of step S126.

  In step S128, the processing content performed by the decrypting unit 84 is decrypted using the RSA encryption method, as in the example of step S204 in the flowchart of FIG.

  In the magnetic recording apparatus according to the second embodiment, the encryption unit encrypts the input data, and a part of the plurality of rows of the data subjected to the first encryption. Can be performed in the second direction. In addition, the decryption unit performs a first decryption in which a part of the plurality of rows of the encrypted data read from the magnetic domain of the magnetic wire by the readout unit is moved in the row direction, and a first decryption And the second decoding for decoding the converted data. Since the number of combinations for selecting some rows is the power of 2 (the number of magnetic fine wires), data encryption can be further strengthened, which is effective in improving security.

  In the magnetic recording apparatus of the second embodiment, an example in which the RSA encryption method is applied as an encryption method has been shown. However, for example, an arbitrary encryption method such as a DES (Data Encryption Standard) encryption method or an ElGamal encryption method is used. You may apply. Since any encryption method can be applied, it is effective in improving security.

  In the second embodiment, the encryption unit encrypts the input data using the RSA encryption method, and a part of the plurality of rows of the data subjected to the first encryption. The example in which the second encryption for moving the row in the row direction has been described. On the contrary, in the first encryption, encryption is performed in which some of the plurality of rows of input data are moved in the row direction, and in the second encryption, the RSA encryption method is used. Encryption may be performed by any encryption method such as.

  In the second embodiment, the decryption unit performs first decryption in which some of the plurality of rows of the read encrypted data are moved in the row direction, and the data subjected to the first decryption. An example has been described in which the second decryption of decrypting the data with the RSA encryption method is performed. On the contrary, in the first decryption, decryption is performed using an arbitrary encryption method such as the RSA encryption method, and in the second decryption, some of the plurality of rows are processed in the row direction. Decoding to be moved to may be performed.

  In the second embodiment, an example has been described in which, when a part of the plurality of lines is moved in the row direction, the movement amount of the part of the lines is the same 1 bit. Accordingly, the amount of calculation can be suppressed while improving the security in the magnetic recording apparatus, which is effective in reducing the cost.

  In the second embodiment, an example in which an operation using Dsh is applied when moving some rows has been described. However, other operations may be applied.

  Hereinafter, an example of a method for manufacturing the magnetic recording device 80 according to the first and second embodiments will be described with reference to FIGS. 9A, 9B, 9C, 9D, and 9E.

  The manufacturing method is performed in the order of FIGS. 9A, 9B, 9C, 9D, and 9E. FIG. 9A will be described. A silicon oxide film 152 (thickness: 200 nm) is formed as an interlayer insulating film on the silicon substrate 150 using CVD (Chemical Vapor Deposition) or the like. Thereafter, a groove for forming the lower electrode film 154 is formed by conventional resist patterning and dry etching. Cu (thickness 400 nm) is deposited on the silicon oxide film 152 by sputtering. Thereafter, the Cu layer is planarized by CMP (Chemical Mechanical Polishing) or the like to form a lower electrode film 154 (thickness 200 nm).

  FIG. 9B will be described. The magnetic fine wire film 156 and the writing part / reading part structure film 158 are continuously formed. As the magnetic fine wire film 156, a ferromagnetic layer NiFe (thickness 30 nm) / CoFeB (thickness 2 nm) can be used. As the writing part / reading part structure film 158, a tunnel oxide film MgO (thickness: 1.0 nm), a ferromagnetic layer CoFeB (thickness: 2.3 nm) of a pinned magnetic layer having a laminated ferri structure / nonmagnetic layer Ru (thickness) 0.8 nm) / ferromagnetic layer CoFe (thickness 1.7 nm) / antiferromagnetic layer PtMn (thickness 100 nm). Further, for example, Ta (thickness: 50 nm) is deposited as the connection electrode film 160. Next, the connection electrode film 160, the writing part / reading part structure film 158, and the magnetic fine wire film 156 are etched by resist patterning and a dry etching method. At this time, processing is performed so that the magnetic wire portion 176 and the reference voltage element portion 178 are electrically separated. Lines and spaces should be 50 nm patterns. The writing unit / reading unit structure film 158 is the reading units 16a to 16p and the writing units 18a to 18p referred to in FIG.

  FIG. 9C will be described. The reading unit corresponding to 170 in FIG. 9E and the writing unit corresponding to 172 in FIG. 9E are processed into a predetermined shape by the same method as described in FIG. For example, the reading unit and the writing unit are processed to a size of 30 nm × 90 nm. However, the etching end point is controlled so that the magnetic fine wire film 156 remains on the surface. A silicon oxide film 162 (thickness of about 200 nm) is formed by CVD or the like. Then, the silicon oxide film 162 is planarized by CMP and etch back. At this time, the connection electrode film 160 is exposed so that electrical connection with the connection electrode film 160 is possible.

  FIG. 9D will be described. Contact holes are formed by resist patterning and dry etching. For example, after depositing a titanium nitride film and a tungsten film as a barrier metal by CVD, these conductive films are etched back or polished back to form plug electrodes 164 embedded in the contact holes. . The plug electrode 164 is electrically connected to the lower electrode film 154 and the magnetic wire film 156.

  With reference to FIG. The upper electrode 168 is formed by film formation, patterning, and processing of Cu (thickness: 200 nm). Finally, a silicon oxide film 166 (having a thickness of about 400 nm) is formed as a protective film by CVD or the like. Thus, the magnetic recording device 80 is completed. In FIG. 9E, 170 surrounded by a broken line 170 is each of the reading units 16a to 16p in FIG. 2, 172 is each of the writing units 18a to 18p of FIG. 2, and 174 is in the read signal processing unit 22 of FIG. This is a reference voltage element used in the comparator circuit.

The above manufacturing method is not limited to the above-described form, and various modifications are possible. For example, the case where the ferromagnetic layer of the fixed magnetization layer of the magnetization thin wire film 156 and the writing unit / reading unit structure film 158 is formed of NiFe, CoFeB, or CoFe has been described, but Co, Ni, Fe, or You may form with ferromagnetic materials, such as these alloys (NiFe, CoFeB, CoFe, etc.). In addition, although the case where the tunnel oxide film of the writing unit / reading unit structure film 158 is formed of MgO has been described, it may be formed of an insulating material such as AlO _x , HfO _x , TiO _x , TaO _x . In addition, although the case where the nonmagnetic layer of the fixed magnetization layer of the writing unit / reading unit structure film 158 is formed of Ru has been described, the nonmagnetic layer is formed of a nonmagnetic material such as Rh, Cu, Al, or Au. May be. In addition, the case where the antiferromagnetic layer of the fixed magnetization layer of the writing unit / reading unit structure film 158 is formed of PtMn has been described, but the antiferromagnetic layer is formed of an antiferromagnetic material such as IrMn or PdPtMn. Also good. Further, although the TMR-spin injection element is used for the writing part / reading part structure film 158, a GMR type may be used. In addition, although the writing unit of the writing unit / reading unit structure film 158 uses a spin injection element, a magnetic field generation wiring for writing in the magnetization direction of the magnetic domain by a current magnetic field may be used.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

FIG. 1 is a block diagram showing the configuration of a conventional magnetic recording apparatus. FIG. 2 is a block diagram illustrating the configuration of the magnetic recording apparatus according to the first and second embodiments. FIG. 3 is a flowchart for writing data according to the first embodiment. FIG. 4A and FIG. 4B are diagrams showing the state of data recorded on the magnetic wire according to the first embodiment. FIG. 5 is a flowchart for reading data according to the first embodiment. FIG. 6 is a flowchart for writing data according to the second embodiment. FIG. 7 is a flowchart for reading data according to the second embodiment. FIG. 8A and FIG. 8B are diagrams showing the state of data recorded on the magnetic wire according to the second embodiment. FIG. 9 is a diagram illustrating a method of manufacturing a magnetic recording apparatus to which the first and second embodiments are applied.

Claims (9)

Including magnetic material, recording data according to the magnetization direction inside the magnetic domain, wherein the magnetic domain is a magnetic wire corresponding to the minimum unit of the data;
A magnetic domain drive unit that moves the magnetic domain by applying a current to the magnetic wire;
An encryption unit for encrypting the input data;
A writing unit for writing encrypted data, which is the data encrypted by the encryption unit, into the magnetic domain of the magnetic wire;
A reading unit that reads the encrypted data written by the writing unit from the magnetic domain of the magnetic wire;
A decryption unit that decrypts and outputs the encrypted data read from the magnetic domain of the magnetic wire by the read unit;
A magnetic recording apparatus comprising: Comprising a plurality of the magnetic wires;
The magnetic recording apparatus according to claim 1, wherein the data has a matrix structure including a plurality of rows and a plurality of columns, and the rows correspond to the magnetic thin wires.   After the writing unit writes the encrypted data, the magnetic domain driving unit moves the magnetic domain by applying a current to the magnetic wire corresponding to some of the plurality of rows. The magnetic recording apparatus according to claim 2, wherein:   After the magnetic domain driving unit moves the magnetic domain by applying a current to the magnetic wire corresponding to some of the plurality of rows, the reading unit is configured to transmit the encrypted data. The magnetic recording apparatus according to claim 2, wherein:   The encryption unit performs a first encryption for encrypting the input data and a second encryption for encrypting the data subjected to the first encryption, and the first and second 3. The magnetic recording apparatus according to claim 2, wherein any one of the encryptions moves a part of the plurality of rows in the row direction.   The decryption unit decrypts the first decrypted data that is decrypted and output the encrypted data read from the magnetic domain of the magnetic wire by the read unit, and decrypts the data that has undergone the first decryption The second decoding is performed, and one of the first and second decoding moves a part of the plurality of rows in a row direction. The magnetic recording device described.   When the magnetic domain driving unit moves the magnetic domains by applying a current to the magnetic wires corresponding to some of the plurality of rows, the movement amounts of the some rows are the same. Or when moving some of the plurality of rows in the row direction, the movement amounts of the some rows are the same. A magnetic recording apparatus according to claim 1.   5. The magnetic recording apparatus according to claim 1, wherein an encryption method of the encryption unit and the decryption unit is any one of RSA, DES, and ElGamal. A magnetic recording method including a magnetic material, recording data according to a magnetization direction inside a magnetic domain, wherein the magnetic domain records the data with respect to a magnetic wire corresponding to a minimum unit of the data,
Moving the magnetic domain by applying a current to the magnetic wire;
Encrypting the input data; and
Writing encrypted data, which is the encrypted data, into the magnetic domain of the magnetic wire;
Reading the written encrypted data from the magnetic domains of the magnetic wire;
Decrypting and outputting the encrypted data read from the magnetic domains of the magnetic wire;
A magnetic recording method comprising:

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