JPH02177743A - Cryptographic system - Google Patents

Abstract

PURPOSE:To reduce the probability of a cryptographic key and a decoding key intercepted by the 3rd party by storing a new cryptographic key generated from a cryptographic key generating means while a sender side and a receiver side are coupled into a cryptographic key storage means at the sender side and a decoding key storage means at the receiver side. CONSTITUTION:A cryptographic key generator 3 generating a cryptographic key KE is provided to the sender side 1. When the system is applied to a cordless telephone set, a master set as the sender side 1 and a slave set as a receiver side 2 are placed near, both coupling sections 8, 14 are coupled and a transfer command of the cryptographic key is outputted by depressing a prescribed switch by the operator. A new cryptographic key KE is generated from the cryptographic key generator 3 in the master set by the transfer command and the new cryptographic key KE is stored in a cryptographic key storage section 4. Thus, the new cryptographic key KE is transferred to the slave set as the receiver side 2 via the coupling sections 8, 14 and the transferred new cryptographic key KE is stored as a decoding key KD into a decoding key storage section 12 in the slave set. Thus, the new cryptographic key KE generated by the cryptographic key 3 is stored to the cryptographic key storage section 4 and the decoding key storage section 12.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a cordless telephone and a cordless terminal.

Regarding encryption methods used in wireless communication technology such as cordless keyboards, more specifically, in order to protect information in wireless communications that can be easily intercepted, transmitted data is encrypted with an encryption key on the transmitting side and sent to the receiving side. This relates to an encryption method in which the sending and receiving side decrypts this using a decryption key.

[Conventional technology]

In order to protect information during communication in fields such as wireless communication, as shown in FIG.
In step 2, the transmission data SD is converted into encrypted data C using the encryption key KB' stored in the encryption key storage section 53, and the transmitted data SD is converted into encrypted data C by the modulator 54.2. It is sent to the receiving full 151 via the antenna 55, and the decoder 56 on the receiving side 51 sends it to the antenna 57. The encrypted data C received by the demodulator 58 is stored in the decryption key storage unit 59.
An encryption method is used in which the received data is decrypted using a decryption key KD stored in the received data RD. Conventionally, this type of encryption system has been used, for example, in the document "Nikkei Electronics, pages 68 to 103 J, published on September 4, 1978," and the document "Nikkei Electronics, pages 89 to 94, published in September 14, 1981. The standard encryption method established by the U.S. Department of Commerce Bureau of Standards (DB
S).

Alternatively, public key cryptography is known. Also in 1981
Literature published on February 2, 2016 [Nikkei Electronics No. 122]
Page J shows the LS of the encryption/decryption circuit for public key cryptography.
The document ``Microsystem Component Handbook'' published by Intel Corporation in 1985 discloses commercially available encryption/decryption LSIs.
is disclosed.

In the Standard Encryption System (DES) established by the U.S. Department of Commerce Bureau of Standards,
The encryption key KE' and decryption key KD' are the same. On the other hand, in public key cryptography, the encryption key K
E' and decryption @KD' are different, and the decryption key K
It is made so that D' cannot be determined from the code @K E'.

[Problem to be solved by the invention] - By the way, in the standard encryption system (DBS), the encryption key KE'
If the information is stolen or leaked due to carelessness and becomes known to a third party, the confidentiality of the information can be kept by using the same decryption key KD' as the encryption key KE' in communications that can be easily intercepted, such as wireless communications. The disadvantage is that it is easily broken. In contrast, in public key cryptography, the encryption key KE
Even if the decryption key KD' is made public and known to a third party, the decryption key KD' cannot be determined from the encryption key KD', so the standard encryption method (
It is possible to protect information better than DBS).

However, even in public key cryptography, if the decryption key KD' is stolen or leaked and becomes known to a third party,
Similar to the standard cryptographic system (DBS), this method has the disadvantage that the confidentiality of information can be easily compromised.

In this way, in the two conventional encryption systems described above, the encryption mKE', the decryption! KD' must be strictly protected from being known to a third party, and in order to apply these encryption methods to low-priced products, special measures must be taken to protect the encryption key KE' and decryption key KD'. The problem is that the algorithm is complex and the amount of hardware required increases.

The present invention does not require the use of complicated algorithms to secure encryption keys, compared to conventional encryption methods.

The purpose of this invention is to significantly reduce the probability that a decryption key will be known to a third party, and to provide an encryption method that is difficult for a third party to decrypt.

[Means to solve the problem]

In order to achieve the above object, the present invention converts transmitted data into encrypted data using an encryption key on the sending side and transmits it to the receiving side, and on the receiving side decrypts the encrypted data sent from the sending side using a decryption key. In an encryption method for obtaining received data, the sending side is provided with an encryption key storage means for storing an encryption key, the receiving side is provided with a decryption key storage means for storing a decryption key, and either the sending side or the receiving side is provided with an encryption key storage means for storing the encryption key. A generating means is provided, and when the sending side and the receiving side are connected, a new encryption key generated from the encryption key generating means is stored in the sending side's encryption key storage means and the receiving side's decryption key storage means. It is characterized by being designed to be memorized.

[Effect]

In the cryptographic system configured as described above, a new cryptographic key is generated from the cryptographic key generation means when the transmitting side and the receiving side are connected. For example, when an encryption key generating means is provided on the sending side, this encryption key is first stored in the sending side's encryption key storage means, and then transferred to the receiving side connected to the sending side, and the receiving side stores the decryption key. stored in the means.

In this way, by generating a new encryption key from the encryption key generation means and storing it in the sending 111Icyi encryption key storage means and the decryption key storage means on the receiving side, the encryption key and decryption key that have been stored in these are removed. Can be changed.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram of a system in which transmitting data SD is converted into ciphertext T on the transmitting side 1 and sent to the receiving side 2, and the ciphertext T is decrypted on the receiving side 2 to obtain received data RD.

In the system shown in FIG. 1, the sending side 1 includes an @encryption key generator 3 that generates an encryption key KE, an encryption key storage section 4 that stores the encryption key KE from the encryption key generator 3, and an encryption key storage section. The transmitted data S is sent using the code glKE stored in
an encoder 5 that encrypts D to generate encrypted data T; and an encoder 5
a modulator 6 that modulates the encrypted data T from the receiver, and an antenna 7 for transmitting the modulated encrypted data T to the receiving side 2.
The transmission (F!1) is further provided with a coupling unit 8 for transferring the encryption key KE stored in the encryption key storage unit 4 to the receiving side 2.

The receiving side 2 also includes an antenna 10 for receiving the encrypted data T transmitted from the transmitting side 1, a demodulator 11 for demodulating the received encrypted data T, and a decryption ga storage section 12 for storing the decryption key KD. and a decoder 13 that decrypts the encrypted data T using the decryption key KD stored in the decryption key storage section 12 to obtain received data RD. A coupling unit 14 is provided for storing the encryption key KE transferred from the transmitting side 1 in the decryption key storage unit 12 as decryption@KD.

The encryption key generator 3 provided on the sending side 1
The coupling part 8 and the reception l\! ! When the coupling unit 14 of I2 is in a coupled state, a new encryption key KE can be generated by a predetermined command. As such a code@generator 3, a known random number generator may be used as long as it generates a sufficiently random signal, but it is preferable to use a generator as shown in FIG. 2, for example. In other words, the generator shown in FIG. 2 includes a physical noise source 20 that generates physical noise by causing breakdown in a diode, etc. A comparator 21 as a binarization means for binarizing and a binary output B from the comparator 21
A shift register 22 inputs D serially, samples it in synchronization with the clock CLK, and outputs a uniformly distributed random number of n-bit binary words; Next, a modulo-n counter (Ilodulo-n counter) 23 returns to "0" again,
The modulo n counter 23 is provided with a latch circuit 1i!24 that latches the parallel output from the shift register 22 every time the modulo n counter 23 becomes 0, for example, and the latch circuit 24 outputs a completely white signal with no repeatability or periodicity. Since a uniformly distributed random number is output, it is preferable to use this as the encryption key generator 3.

Further, when transmitting the encrypted data T by radio waves, the modulator 6 on the transmitting side 1 typically uses an RF modulation method using the FSX modulation method.
The modem consists of a demodulator 2 on the receiving side and I on the transmitting side.
It is compatible with the modulator 6 of. Also, sending side 1
．． The coupling part 8.14 on the receiving side 2 may be of the type 6 in which one is inserted into the other and tightly coupled to each other, such as a metal connector, or it may be an electromagnetic (L-lance) type connector.
Types of coupling without close coupling, such as coupling, electric field (capacitor) coupling, optical coupling, etc., may be used.For types of coupling without close coupling, the receiving side 1 does not have to come into direct contact with the transmitting side 2, making it less susceptible to mechanical damage.

The operation when a system having such a configuration is applied to a cordless telephone will be described next.

Currently, the base unit of a cordless phone has the function of transmitter 1, and the slave unit has the function of receiver 112.
A case will be described in which transmission data SD is transmitted from a master device serving as a transmitting side 1 to a slave device serving as a receiving side 2. It is assumed that the handset is of a portable size.

When the cordless telephone is not in use, the slave unit is placed near the base unit, and the connecting parts 8 and 14 of both are in a connected state. When the coupling parts 8.14 are formed, for example, by metal connectors, the coupling parts 14 are inserted into the coupling parts 8 and brought into close contact with each other.

When this state is reached, the encryption key KE is released by the operation of a microswitch or the like (not shown) that detects the connection of the connection part 8.14, or by the operator pressing a predetermined switch (not shown). A transfer command is issued.

In response to this transfer command, the base unit serving as the sending side 1 causes the encryption key generator 3 to generate a new encryption key KE, and stores this new encryption key KE in the encryption key storage section 4. After that, the new encryption key KE stored in the encryption key storage section 4 is received via the coupling sections 8 and 14! Transfer the new encryption key KE to the slave device as f2, and the slave device uses the transferred new encryption key KE as the decryption key KD.
The decryption key is stored in the decryption key storage unit 12 as .

In this way, the new encryption key KE generated with encryption key 3
The encryption key storage unit 4. The decryption key can be stored in the decryption key storage unit 12.

When a cordless telephone is used, the slave unit is generally located at a location separate from the S unit.

The base device as the transmitting side 1 uses the encryption key KE stored in the encryption key storage section 4 in the encoder 5 to transmit data S.
D into encrypted data T, and modulator 6. Receive via antenna 7 (for example, send to the slave unit as F!2 by radio waves. The slave unit receives the encrypted data T from the base unit by radio waves via the antenna 10 demodulator 11, and decodes it in the decoder 13. Using the decryption key KD stored in the key storage unit 4, the encrypted data 'r is converted into received data RT) and output. As a result, the slave device can obtain received data RD that is the same as transmitted data SD.

When you no longer use the cordless phone, place the handset close to the base unit again and connect the connection part 8 of the handset to the connection part 14 of the base unit.
be combined with. By issuing a transfer command in this state, the encryption key generator 3 will issue a new encryption key KE again.
is generated and stored in the encryption key storage unit 4. As a result, the secret key KE previously stored in the encryption key storage section 4 is replaced and changed with the new encryption key KE. Thereafter, this new encryption key KE is transferred to the handset via the coupling units 8 and 14 and stored in the decryption key storage unit 12 as a decryption key. As a result, the decryption key KD previously stored in the decryption key storage section 12 is replaced and changed by the new decryption IIKD. Therefore, when using the cordless telephone again, it is possible to encrypt the transmitted data SD and decrypt the encrypted data T using an encryption key KE and decryption key KD that are different from the encryption gxE and decryption key KD that were previously used. can.

In this way, in this repair example, we will decrypt the slave unit while the master unit and slave unit are connected! Since the KD is transferred directly from the base unit, if the coupling parts 8 and 14 are closely connected with a metal connector, the encryption key KE and decryption will be decrypted as long as a third party does not touch the base unit directly. The IKD can be protected and the coupling parts 8 and 14 are electromagnetic and electric coupled.

In the case of optical coupling, etc., it is difficult for a third party to steal the encryption key KE even if they touch the base unit, so the encryption key KE can be decrypted! The IKD can be effectively protected, and the probability that the IKD will end up in the hands of a third party due to carelessness or the like can be significantly reduced.

Code again! KE and decryption key KD can be changed using the simple procedure described above, thereby increasing the probability that a third party will know what the encryption key KE and decryption key KD are currently. Significantly reduced. Note that this probability decreases as changes are made more frequently. Therefore, even if the encryption key KE and decryption key KD were stolen in the past and became known, the current encryption key KE and decryption key KD are generated by the generator shown in FIG. When something does not have reproducibility or periodicity, it is impossible to algorithmically estimate the current encryption key KE and decryption key KD, so it becomes impossible to extract them, and the conventional standard Compared to cryptographic systems (DBS) and public key cryptosystems, it is possible to maintain the confidentiality of telephone calls at an extremely high level in a short period of time.

Note that in the above configuration, the encoder 5. Since the decoder 13 may be a simple one that does not require any complicated algorithms for security, the encryption system of this embodiment can be applied to low-cost products.

In the above-described embodiment, the encryption key generator 3 is provided on the transmitting side 1, but the encryption key generator 3 is provided on the transmitting side 1. In this case, the decryption key KD is stored in the decryption key storage 12 and then stored in the encryption key storage 4 of the sending side 1 via the coupling unit 14.8.

Furthermore, in the above embodiment, the encryption key KE and the decryption key KD are made the same, but the idea of the present invention can also be applied in principle to a public key cryptosystem in which the encryption key KE and the decryption key KD are different. It is possible to apply. However, when applied to public key cryptography, when changing the encryption key KE and decryption key KD, it generally requires multiple calculations to find the decryption 9KD corresponding to the encryption key KE, so and the encryption key KE.

There is a problem that it is difficult to change the decryption key KD.

Further, in the above embodiment, the base unit of the cordless telephone has the function of transmitting side 1, and the handset has the function of receiving side 2, but each of the base unit and handset has the function of transmitting side 1.
It is preferable to provide both R functions on the receiving side 2. In this case, transmission from the slave unit to the base unit is also possible. At this time, the base unit as transmitting side 1, the encryption key KE of the slave unit as receiving side 2, the decryption key KD, the base unit as receiving side 2, the encryption key KE of the slave unit as transmitting side 1, the decryption key K If you want D to be different from each other, you only need to generate the encryption key twice from one encryption key generator at different timings, and if you want to make them the same, you need to generate one encryption key from one encryption key generator.
All you need to do is generate the encryption key.

Further, in the above embodiment, the encrypted data T is transmitted from the transmitting side 1 to the receiving side 2 using radio waves, but this transmission may also be performed using sound waves or light. In this case, the modulator 6. As the demodulator 11, one suitable for transmitting and receiving sound waves and light is selected.

〔Effect of the invention〕

As explained above, according to the present invention, an encryption key generation means is provided on either the sending side or the receiving side, and when the sending side and the receiving side are connected, the encryption key generation means The new encryption key generated from the encryption key is stored in the sending side's encryption key storage means and the receiving side's decryption key storage means.

The decryption key can be easily changed in a state where it is difficult for a third party to obtain it, and the encryption key and decryption key can be easily changed by a third party without using complicated algorithms for security. It is possible to significantly reduce the probability that the information will be known by someone else, making it difficult for a third party to decipher it.

Figure 1

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a system to which the encryption method of the present invention is applied, Fig. 2 is a diagram without showing an example of an encryption key generator, and Fig. 3 is a block diagram of a system to which the conventional encryption method is applied. .

Claims (1)

[Claims] In an encryption method, the sending side converts the sent data into encrypted data using an encryption key and sends it to the receiving side, and the receiving side decrypts the encrypted data sent from the sending side using the decryption key to obtain the received data. An encryption key storage means for storing the encryption key is provided on the receiver side, a decryption key storage means for storing the decryption key is provided on the receiving side, an encryption key generation means is provided on either the sender side or the receiver side, and the sending side and the receiver are provided with an encryption key storage means for storing the encryption key. A new encryption key generated from the encryption key generation means is stored in the encryption key storage means of the sending side and the decryption key storage means of the receiving side when the two sides are connected. encryption method.