JPH04264922A - Program input circuit and program transferring method for information processor - Google Patents

Abstract

PURPOSE:To improve the versatility of a digital signal processor (DSP) by providing a decoding circuit to decode an encoded program on the basis of a decoding code taken out by a control circuit. CONSTITUTION:At the time of operating the DSP 11, at first, a microcomputer 12 sends a control signal to the DSP 11, and afterwards, it starts the serial transfer of a decoding key code and the encoded program in order. A decoding key extraction circuit 4 is turned into an operating state by the impressing of the control signal, and when it inputs the decoding key code transferred first by eight bits, it sends this decoding key code to the decoding circuit 15 so as to preset it in a random number generation circuit in the decoding circuit 15. The decoding circuit 15 decodes the program by taking the E-OR output of a random number generated successively and the instruction code of the encoded program inputted successively.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a program input circuit of an information processing device in which a memory for storing a program is constituted by a RAM (Random Access Memory) and a program is loaded into the RAM from the outside, and a program transfer method. Regarding.

0002

[Prior Art] Generally, DSP (digital signal processor)
Processors) are used in a wide range of fields because they can perform various digital processes according to programs. Generally, a DSP formed on a single semiconductor substrate has a built-in SRAM for receiving programs from the outside and storing the programs in order to provide versatility. However, since there are terminals and wiring for supplying the program from an external device to the DSP, a third party can easily take out the program from these terminals and wiring.
Program secrets may be leaked.

[0003] Conventionally, a method of leaking secrets has been realized by creating a program, encrypting it, sending it to the DSP, and decrypting it according to a decryption key held on the DSP side. FIG. 4 is a block diagram of a system using conventional program creation and DSP.
1 is a program development device, 2 is an encryption device, 3 is a DSP
, 4 is a microcomputer for supplying programs to the DSP.

[0004] In FIG. 4, the program creator
A processing program to be executed by P3 is created by the program development device 1. The created program is
It is encrypted by the encryption device 2 based on a specific encryption key. This encryption is performed, for example, by obtaining an E-OR output between the output of a random number generator with a preset encryption key and the program code. The encrypted program is stored in the ROM of the microcomputer 4 that controls the DSP 3.
5 along with the microcomputer program.

[0005] When operating the DSP 3, the encrypted program held in the ROM 5 of the microcomputer 4 is
Transfer to SP3. The DSP3 has previously set the RO inside the DSP3.
The M6 holds the decryption key corresponding to the encryption key,
The encrypted program transferred using this held decryption key is decrypted into the original program by the decryption circuit 7,
The decrypted program is stored in SRAM for program storage.
8 is stored.

[0006]

According to the system shown in FIG. 4, since the decryption key is permanently stored in the ROM 6 of the DSP 3, the DSP 3 can be used only by the user who uses the encryption key and the decryption key. Available and 3rd
could not be used by anyone. That is, the advantage of improving the versatility of the DSP by configuring the program memory with SRAM is disadvantageously hindered.

[0007]

[Means for Solving the Problem] The present invention was created in view of the above points, and a decryption key code for decrypting an encrypted program and an encrypted program are input. A decryption key extraction circuit that is operated by a control signal previously applied from an external control device and extracts a decryption key code that is subsequently input, and a program that is encrypted based on the decryption key code extracted by the control circuit. By including a decoding circuit that decodes the data, the versatility of the information processing device (DSP) is improved.

[0008]

[Operation] According to the present invention, since there is a decryption key extraction circuit inside the DSP for extracting the decryption key, the decryption key can be extracted by placing the decryption key at the beginning of the encrypted program and transferring it to the DSP. Since the encrypted program that is taken out into the DSP and transferred thereafter is decrypted based on this decryption key, the user can freely set the encryption key and decryption key, and the versatility of the DSP can be ensured.

[0009]

[Embodiment] FIG. 1 is a block diagram showing an embodiment of the present invention, in which 9 is a program development device, 10 is an encryption device, and 11 is a block diagram showing an embodiment of the present invention.
is a DSP, and 12 is a control microcomputer. The program creator uses the program development device 9 to create a processing program to be executed by the DSP 11, as in the past. The created program is encrypted by the encryption device 10, but at this time, the program creator
Enter any encryption key code in 0. The encryption key code is composed of, for example, 8 bits.

[0010] The encryption method is performed by E-ORing an 8-bit random number code sequentially obtained by presetting an encryption key code into a random number generation circuit (not shown) and an 8-bit instruction code constituting the program. It is something to do. The decoding method performed by the DSP 11 is exactly the same. Details will be described later. The encrypted program must first have the encryption key code, i.e. the decryption key code, DS
When the microcomputer 12 is manufactured, it is written into the ROM 13 together with the encrypted program so as to be transferred to the P11.

On the other hand, the program input circuit of the DSP 11 connected to the program transfer terminal of the microcomputer 12 is
It is roughly composed of a decryption key extraction circuit 14 and a decryption circuit 15. In order to operate the DSP11, the microcontroller 12
first sends a control signal to the DSP 11, and then starts serial transfer of the decryption key code and the encrypted program in that order. The decryption key extraction circuit 14 enters the operating state by applying a control signal, and when the first 8 bits of the decryption key code that is transferred is input, this decryption key code is sent to the decryption circuit 15, and the random number generation circuit in the decryption circuit 15 outputs the decryption key code. (described later). The decryption circuit 15 decrypts the program by obtaining an E-OR output of sequentially generated random numbers and sequentially input encrypted program instruction codes.

The instruction codes of the decoded programs are sequentially written into the SRAM 16 which stores the programs. When the decoding and writing of the program is completed, DSP1
1 performs signal processing specified by a program by sequentially addressing the SRAM 16 with a program counter (not shown). Next, DSP1 shown in FIG.
FIG. 2 shows a detailed circuit block of the program input circuit No. 1.

In FIG. 2, the decryption key extraction circuit 14 is
Control signal CO output from microcomputer 12 to terminal SIN
FF (flip-flop) 17 to which NT is applied to the set terminal S, and the output Q of FF17 is applied to the output CNT.
AND gate 18 to which D is applied to the reset input R of FF17, and AND gate 18 to which the inverted output *Q of FF17 is applied.
It consists of a gate 19.

The decryption circuit 15 also includes an E-OR gate 21 connected to a data input terminal DIN to which a decryption key code and an encrypted program serially transferred from the microcomputer 12 are applied, and an E-OR gate 21 whose output is connected to an E-OR gate DIN. OR gate 21
It is composed of an AND gate 22 which is connected to one input and has the inverted output *Q of the FF 17 applied to one of its inputs, and a random number generation circuit 23 whose output is applied to the other input of the AND gate 22. Here, the random number generation circuit 23 uses a transfer clock SC applied from the microcomputer 12 to the clock input terminal CIN.
For example, an 8-bit shift register 24 controlled by K and a predetermined 2-bit output of the shift register 24 are applied, and the output is applied to the data input D of the shift register 24.
The E-OR gate 25 is connected to the E-OR gate 25.

Furthermore, the program input circuit includes a counter 26 which applies the output OVC to the AND gates 18 and 19 every time eight transfer clocks SCK applied to the clock input terminal CIN are counted, and an E-OR gate 21. A shift register 27 whose output is connected to the data input D and performs a shift operation in accordance with the transfer clock SCK; a transmission gate 28 which is controlled by the output CNTD of the AND gate 18 and presets the data in the shift register 27 to the shift register 24; A transmission gate 29 that is controlled by the output CNTP of the gate 19 and transmits data from the shift register 27, and a latch circuit 30 that holds the data transmitted from the transmission gate 29 and outputs the data to a program RAM (not shown). have.

Next, the operation of the program input circuit shown in FIG. 2 will be explained with reference to the operation timing diagram of FIG. First, before transferring the decryption key code and the encrypted program, the control signal CONT is output as an "H" level pulse. The rise of the control signal CONT sets the FF 17 and resets the counter 26. As a result, the output Q of the FF 17 becomes "H" level and the AND gate 18 opens, and the output *Q becomes "L" level and the AND gate 19 closes.

Next, a decoding key code consisting of 8 bits is applied to the DSP 11 using the transfer clock SCK. At this time, since the output *Q of the FF 17 is at the "L" level, the output of the AND gate 22 is at the "L" level. Therefore, the E-OR gate 21 connects the data input terminal DIN
The decryption key code applied to is output as is. Therefore, the shift register 27 uses the transfer clock S
The decryption key code is sequentially shifted by CK. On the other hand, the counter 26 starts counting this transfer clock SCK, and when the count value reaches "8", that is, when all 8 bits of the decryption key code are taken into the shift register 27, as shown in FIG. , outputs an "H" level output OVC equal to the pulse width of the transfer clock SCK. This output O
VC is connected to the output C through the AND gate 18 which is open.
It is output as NTD and opens the transfer gate 28. As a result, the decryption key code taken into the shift register 27 is preset into the shift register 24 of the random number generation circuit 23.

Further, the output CNTD is applied to the reset input R of the FF 17, the FF 17 is reset, the output Q becomes the "L" level, and the output *Q becomes the "H" level. As a result, AND gate 18 is closed and AND gate 19 is closed.
and AND gate 22 is opened. After that, the sequentially encrypted programs are transferred to the DSP using the transfer clock SCK.
11. At this time, each time the transfer clock SCK is applied, the shift register 24 of the random number generation circuit 23 sequentially outputs a random number created based on the decryption key code one bit at a time. This random number output is an open A
It is output from the ND gate 22 to the E-OR gate 21. Therefore, the encrypted program applied to the data input terminal DIN is added bit by bit to the random number output by the E-OR gate 21 and applied to the shift register 27. That is, decryption of an encrypted program is E-O
This is accomplished by the R gate 21.

On the other hand, the counter 26 counts the transfer clock SCK of the encrypted program, and when the count value is "8",
The output OVC is output every time. This output OVC is
In order to output the output CNTP of the open AND gate 19, the transfer gate 29 opens and the shift register 2
The 8-bit decoded program loaded into the 8-bit program is transferred to the latch circuit 30 and latched. Latch circuit 3
The program latched to 0 is stored in S for holding the program while the shift register 27 is being shifted.
The data is sequentially transferred and stored in RAM.

[0020] In this way, by first sending the decryption key code from the microcomputer and then sending the encrypted program, the decryption key code is taken out to the DSP 11 and the encrypted program is decrypted. At this time,
The decryption key and the encrypted program will be known to a third party through the data input terminal DIN, but unless the type of random numbers generated by the decryption key or the system for generating random numbers is known, the program cannot be accessed. It is difficult to decipher and can protect the secret of the program.

[0021]

As described above, according to the present invention, since the program input circuit of the DSP is equipped with the function of extracting and decoding the decoding key code, there is an advantage that the user can set the decoding key code arbitrarily, and that the DSP can Since it is not limited to specific users, the versatility of DSP is not hindered.

[Brief explanation of the drawing]

FIG. 1 is a system block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram of a program input circuit showing an embodiment of the present invention.

FIG. 3 is a timing diagram showing the operation of the block diagram shown in FIG. 3;

FIG. 4 is a system block diagram showing a prior art.

[Explanation of symbols]

9 Program development device 10
Encryption device 11 DSP 12 Microcomputer 13 ROM 14 Decryption key extraction circuit 15
Decoding circuit 16 SRAM 17 FF 18, 19 AND gate 21 E-OR gate 22
AND gate 23 Random number generation circuit 24 Shift register 2
5 E-OR gate 26
Counter 27 Shift register 28, 29
Transfer gate 30 latch circuit

Claims (2)

[Claims] Claim 1: A program input circuit for inputting a program encrypted according to a predetermined rule from an external control device, comprising: a decryption key code for decrypting the encrypted program; and a decryption key code for inputting the encrypted program. A decryption key extracting circuit that operates according to a control signal applied from the external control device in advance and extracts the decryption key code; and a decryption key extraction circuit that extracts the decryption key code from the control circuit; A program input circuit for an information processing device, comprising a decoding circuit for decoding. 2. A program transfer method for transferring a program encrypted according to a predetermined rule from an external control device to an information processing device, comprising: a composite key code corresponding to an encryption key code used when encrypting the program; The method is characterized in that the encrypted program is stored in a storage device inside the external control device, and after the composite key code is transferred to the information processing device, the encrypted program is transferred to the information processing device. Program transfer method.