Network security communication method, storage medium, device and computer program product based on improved enhanced quantum security encryption algorithm

Abstract

The present invention discloses a network security communication method, storage medium, device and computer program product based on an improved enhanced quantum security encryption algorithm, including: before network communication, the message sender adopts an improved quantum key distribution technology to send a quantum bit sequence to the message receiver through a quantum channel to generate a shared quantum key; quantum state tomography technology and quantum entanglement purity test are used to test the security of the shared quantum key, the message sender and the message receiver adopt a quantum key conversion method based on hyperentanglement to convert the shared quantum key stored in the quantum key pool into a classical key, and the classical key is regularly updated and stored in the classical key pool; in each network communication, the message sender encrypts the plaintext to be transmitted using the classical key to obtain the ciphertext, transmits the ciphertext to the message receiver, and the message receiver decrypts the ciphertext. The present invention improves the security of network communication.

Description

Technical Field

[0001] The present invention relates to the field of network security protection technology, and in particular to a network security communication method, storage medium, device and computer program product based on an improved and enhanced quantum security encryption algorithm. Background Art

[0002] Network security communication is a vital part of the information technology field. It involves protecting network connections, data transmission, and various network services from unauthorized access and various network attacks. Traditional network security communication methods mainly rely on classical cryptographic algorithms, including but not limited to symmetric encryption algorithms, asymmetric encryption algorithms, hash functions, and elliptic curve cryptography.

[0003] Although these traditional encryption algorithms play an important role in protecting current network communications, they have some inherent limitations and drawbacks:

[0004] 1. Fragility of mathematical foundations: The security of most classical encryption algorithms relies on the computational difficulty of certain mathematical problems, such as large number decomposition and discrete logarithm problems. With the improvement of computing power, especially the development of quantum computers, the computational difficulty of these problems may be greatly reduced, making traditional algorithms vulnerable and unable to provide sufficient network security protection for information transmission;

[0005] 2. Complexity of key management: In an asymmetric encryption system, the key generation, distribution and storage process is relatively complex. Improper key management may lead to key leakage, thus threatening the security of the entire network communication system.

[0006] 3. Computational and storage overhead: Some encryption algorithms have limitations in key length and computational efficiency, which can lead to significant performance bottlenecks as the amount of data increases, affecting the performance and scalability of the entire network system;

[0007] 4. Limitations in adaptability and flexibility: With the development of emerging technologies, such as the Internet of Things, cloud computing, and big data, existing encryption methods may find it difficult to adapt to the security challenges brought about by these new technologies;

[0008] 5. Insufficient ability to resist quantum attacks: The emergence of quantum computers means that many existing encryption algorithms can be quickly cracked, and existing network security protection methods are particularly vulnerable to quantum attacks. Summary of the invention

[0009] In response to the problems existing in the prior art, the present invention provides a network security communication method, storage medium, device and computer program product based on an improved enhanced quantum security encryption algorithm, which improves the security of network communications.

[0010] To achieve the above technical objectives, the present invention adopts the following technical solution: a network security communication method based on an improved enhanced quantum security encryption algorithm, specifically comprising the following steps:

[0011] Step 1: During network communication, set up the quantum key pool and the classical key pool;

[0012] Step 2: Before different message senders and message receivers communicate over the network, the message sender uses an improved quantum key distribution technology to send a quantum bit sequence to the message receiver through a quantum channel. The message receiver receives the quantum bit sequence and exchanges information with the message sender on a public channel to generate a shared quantum key.

[0013] Step 3: Use quantum state tomography technology and quantum entanglement purity test to test the security of the shared quantum key. If it meets the security requirements, it will be stored in the quantum key pool, otherwise it will be discarded;

[0014] Step 4: The message sender and the message receiver use a quantum key conversion method based on hyper-entanglement to convert the shared quantum key stored in the quantum key pool into a classical key, and regularly update the classical key and store it in the classical key pool;

[0015] Step 5: During each network communication, the message sender encrypts the plaintext to be transmitted using the corresponding classic key in the classic key pool to obtain the ciphertext, and transmits the ciphertext to the message receiver;

[0016] Step 6: After receiving the ciphertext, the message recipient decrypts the ciphertext using the same classic key.

[0017] Furthermore, the generation process of the shared quantum key in step 2 is specifically as follows:

[0018] Q=EC(|ψ>,Cerror)

[0019] Where Q represents the shared quantum key, EC() represents the error correction coding function, and |ψ> represents the high-dimensional quantum entangled state key received by the message receiver. d represents the length of the quantum bit sequence, i represents the index of d, |i> A represents the ground state information of the i-th quantum ratio in the message sender, |i> B represents the ground state information of the i-th quantum bit in the message receiver, represents the symbol of tensor product, and Cerror represents the error detection result.

[0020] Furthermore, the specific process of performing security testing on the shared quantum key in step 3 is as follows:

[0021]

[0022]

[0023] Among them, ρ reconstructed represents the reconstructed shared quantum key state, |ψ> represents the high-dimensional quantum entangled state key received by the message receiver, u and v both represent Pauli matrix measurements in the x, y or z direction, M uv represents the measurement matrix, P v represents the probability when v is measured under the corresponding Pauli matrix, r v Represents the correlation coefficient when v is measured under the corresponding Pauli matrix.

[0024] Furthermore, the specific process of converting the shared quantum key stored in the quantum key pool into a classical key in step 4 is:

[0025] Step 4.1: The message sender performs a ground state measurement on each quantum bit in the shared quantum key to obtain a first measurement result. The message sender sends the first measurement result to the message receiver through a secure classical communication channel, and the message receiver receives the communication result.

[0026] Step 4.2, the message receiver selects a base state corresponding to the message sender, performs base state measurement on the communication result, and obtains a second measurement result;

[0027] Step 4.3, determine whether the first measurement result and the second measurement result are the same, if they are the same, retain the measurement result, otherwise discard it;

[0028] Step 4.4: Concatenate all retained measurement results to form the classical key.

[0029] Furthermore, the update process of the classic key in step 4 is as follows:

[0030] i. Use the quantum key mixing protocol combined with quantum random numbers to mix the classical key and obtain the mixed classical key K C，mixed :

[0031]

[0032] Where C represents the classical secret key, R1 represents the first random number generated by the quantum random number generator, and H() represents the hash function. Represents a bit-level XOR operation;

[0033] ii. Update the hybrid classical key with the shared quantum key to obtain the updated classical key K C，new :

[0034] K C，new =HKDF(KC，mixed , Q)

[0035] Among them, Q represents the shared quantum key, and HKDF() represents the key derivation function.

[0036] Furthermore, the process of obtaining the ciphertext in step 5 is:

[0037]

[0038] Where K represents the ciphertext, represents an encryption function that depends on the classical key in the classical key pool, M represents the plaintext to be transmitted, R2 represents the second random number generated by the quantum random number generator, Represents a bit-wise exclusive-or operation.

[0039] Furthermore, the process of decrypting the ciphertext in step 6 using the same classic key is:

[0040]

[0041] in, Represents the third random number generated by the R3 quantum random number generator, a decryption function that depends on the classical key in the classical key pool.

[0042] Furthermore, the present invention also provides a computer-readable storage medium storing a computer program, wherein the computer program enables a computer to execute the network security communication method based on the improved enhanced quantum security encryption algorithm.

[0043] Furthermore, the present invention also provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the network security communication method based on the improved enhanced quantum security encryption algorithm is implemented.

[0044] Furthermore, the present invention also provides a computer program product, including a computer program, which, when executed by a processor, implements the network security communication method based on the improved enhanced quantum security encryption algorithm.

[0045] Compared with the prior art, the present invention has the following beneficial effects: the network security communication method based on the improved enhanced quantum security encryption algorithm of the present invention adopts an improved quantum key distribution technology to generate a shared quantum key, and fully utilizes the advantages of quantum entanglement, that is, the quantum bit sequences are mutually correlated, and the consistency and security of high-dimensional entangled state keys can be maintained even in long-distance transmission. In addition, combined with efficient quantum error correction coding technology, it can detect and correct errors that may occur during the transmission of high-dimensional entangled state keys, thereby enhancing the stability and accuracy of shared quantum key transmission. Therefore, the present invention can provide more secure and reliable communication guarantees at the quantum level through the improved quantum key distribution technology, ensuring the key distribution process. High reliability provides a solid foundation for network security communications; the security of shared quantum keys is tested through quantum state tomography technology and quantum entanglement purity test, which further verifies the purity of entangled shared quantum keys and eliminates any possible pollution caused by environmental interference or malicious intervention. It can effectively defend against advanced attacks on quantum key distribution, build a solid line of defense for quantum communication networks, and ensure the absolute security and privacy protection of information transmission; adopt a quantum key conversion method based on hyper-entanglement to convert the shared quantum keys stored in the quantum key pool into classical keys, and update the classical keys to ensure the consistency and accuracy between quantum keys and classical keys, thereby improving the security of network communications. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The present invention is a flow chart of a network security communication method based on an improved enhanced quantum security encryption algorithm. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further explained below in conjunction with the accompanying drawings.

[0048] like Figure 1 The flowchart of the network security communication method based on the improved enhanced quantum security encryption algorithm of the present invention is as follows:

[0049] Step 1: During network communication, set up the quantum key pool and the classical key pool.

[0050] Step 2: Before different message senders and message receivers communicate over the network, the message sender uses an improved quantum key distribution technology to send a quantum bit sequence to the message receiver through a quantum channel. The message receiver receives the quantum bit sequence and exchanges information with the message sender on a public channel to generate a shared quantum key. Specifically, the improved quantum key distribution technology of the present invention uses a high-dimensional quantum entangled state to generate a high-dimensional quantum entangled state key from the quantum bit sequence. The use of a high-dimensional quantum entangled state enhances the transmission security of the quantum key because the high-dimensional quantum entangled state has a stronger anti-interference ability, which reduces the risk of information being intercepted and tampered with during transmission. The quality of the high-dimensional quantum entangled state key is improved through quantum error correction coding technology, thereby obtaining a shared quantum key. The present invention uses the basic principles of quantum mechanics, especially quantum entanglement and non-cloning, to ensure the security of the key generation and distribution process. By using high-dimensional quantum entangled states, the generation rate and quality of shared quantum keys are improved, and the information transmission rate of quantum channels is increased. At the same time, the application of quantum error correction coding enhances the resistance to errors that may occur during the transmission process, ensuring the accuracy and stability of the shared quantum key transmission process. This process is a means for the message sender and the message receiver to authenticate their identities. Only when the expected communication parties can successfully complete the exchange of shared quantum keys, the legitimacy of each other's identities can be indirectly confirmed.

[0051] The generation process of the shared quantum key of the present invention is specifically as follows:

[0052] Q=EC(|ψ>,Cerror)

[0053] Where Q represents the shared quantum key, EC() represents the error correction coding function, and |ψ> represents the high-dimensional quantum entangled state key received by the message receiver. d represents the length of the quantum bit sequence, i represents the index of d, |i> A represents the ground state information of the i-th quantum ratio in the message sender, |i> B represents the ground state information of the i-th quantum bit in the message receiver, represents the symbol of tensor product, and Cerror represents the error detection result.

[0054] Step 3: Use quantum state tomography technology and quantum entanglement purity test to test the security of the shared quantum key. If it meets the security requirements, it will be stored in the quantum key pool, otherwise it will be discarded. The implementation of the security test ensures that only the shared quantum key that meets the specific security standards will be adopted, thereby greatly reducing the risk of shared quantum key leakage and improving the security and reliability of the entire network communication. Specifically, the specific process of security testing of the shared quantum key is as follows:

[0055]

[0056]

[0057] Among them, ρ reconstructed represents the reconstructed shared quantum key state, |ψ> represents the high-dimensional quantum entangled state key received by the message receiver, u and v both represent Pauli matrix measurements in the x, y or z direction, M uv represents the measurement matrix, P v represents the probability when v is measured under the corresponding Pauli matrix, r v represents the correlation coefficient when v is measured under the corresponding Pauli matrix. reconstructed =1, it indicates that the quantum channel of network communication is in a pure state, the shared quantum key security verification is passed, and step 4 is executed; when ρ reconstructed <1, it indicates that the quantum channel of network communication is in a mixed state, the shared quantum key security verification fails, and needs to be abandoned; in general, there is no ρ reconstructed >1, if ρ reconstructed >1 indicates that the shared quantum key is invalid and needs to be discarded. The present invention tests the security of the shared quantum key and retains the pure shared quantum key, which can prevent potential eavesdroppers from obtaining information by increasing the hybridity of the network communication system.

[0058] Step 4: The message sender and the message receiver use a quantum key conversion method based on hyperentanglement to convert the shared quantum key stored in the quantum key pool into a classical key, ensuring the consistency and accuracy between the quantum key and the classical key, thereby improving the security of network communications and improving the efficiency and anti-attack capabilities of key conversion; regularly update the classical key, store it in the classical key pool, and use the quantum key mixing protocol and quantum random number generator to dynamically update the classical key, increasing the unpredictability of the classical key, thereby improving the security of network communications and reducing the risk of leakage; at the same time, regular updates of the classical key also help to establish trust between the message sender and the message receiver, while providing the necessary flexibility to quickly respond to security incidents, ensuring the long-term security and reliability of communications. Specifically include the following sub-steps:

[0059] Step 4.1: The message sender performs a ground state measurement on each quantum bit in the shared quantum key to obtain a first measurement result. The message sender sends the first measurement result to the message receiver through a secure classical communication channel, and the message receiver receives the communication result.

[0060] Step 4.2, the message receiver selects a base state corresponding to the message sender, performs base state measurement on the communication result, and obtains a second measurement result;

[0061] Step 4.3: Determine whether the first measurement result and the second measurement result are the same. If they are the same, retain the measurement result, indicating that the quantum channel is not disturbed by the outside world. Therefore, no eavesdropping behavior is detected during the distribution of the shared quantum key, thereby ensuring the security and validity of the shared quantum key. Otherwise, discard it. This process is a key step to ensure that the quantum key shared between the communicating parties is not intercepted or tampered with by a third party, providing a secure foundation for the subsequent generation of the classical key, thereby ensuring the security of the entire communication process.

[0062] Step 4.4, concatenate all retained measurement results to form a classical key;

[0063] Step 4.5: Use the quantum key mixing protocol combined with quantum random numbers to mix the classical key and obtain the mixed classical key K C，mixed :

[0064]

[0065] Where C represents the classical secret key, R1 represents the first random number generated by the quantum random number generator, and H() represents the hash function. Represents a bit-level XOR operation;

[0066] Step 4.6: Update the hybrid classical key with the shared quantum key to obtain the updated classical key K C，new :

[0067] K C，new =HKDF(K C，mixed , Q)

[0068] Among them, Q represents the shared quantum key, and HKDF() represents the key derivation function.

[0069] Before the message sender uses the corresponding classical key in the classical key pool to encrypt the plaintext to be transmitted, the message sender can use the shared quantum key generated by the improved quantum key distribution technology to digitally sign the plaintext to be transmitted, which can ensure the integrity of the plaintext to be transmitted and the verification of the identity of the message sender, while ensuring the unconditional security of the digital signature.

[0070] Step 5. During each network communication, the message sender encrypts the plaintext to be transmitted using the corresponding classic key in the classic key pool to obtain the ciphertext, and transmits the ciphertext to the message receiver. The encryption and decryption process of the plaintext to be transmitted using the classic key combines the high security of the quantum-safe encryption algorithm with the efficiency, maturity and compatibility of the classic encryption technology, provides end-to-end data protection, ensures that the data always remains encrypted during transmission, enhances the reliability of identity authentication and digital signatures, ensures that the data always remains encrypted during transmission, and can only be decrypted and viewed by the communicating parties, effectively protecting user privacy, especially in cloud computing and IoT environments. In addition, this process ensures the security and practicality of network communications while maintaining compatibility with existing technologies, providing a comprehensive and efficient solution for modern network security communications.

[0071] The process of obtaining the ciphertext in the present invention is as follows:

[0072]

[0073] Where K represents the ciphertext, represents an encryption function that depends on the classical key in the classical key pool, M represents the plaintext to be transmitted, R2 represents the second random number generated by the quantum random number generator, Represents a bit-wise exclusive-or operation.

[0074] Step 6: After receiving the ciphertext, the message recipient decrypts the ciphertext using the same classic key:

[0075]

[0076] in, Represents the third random number generated by the R3 quantum random number generator, a decryption function that depends on the classical key in the classical key pool.

[0077] After the message recipient uses the same classical key to decrypt the ciphertext, he can use the corresponding quantum-safe method to verify the digital signature provided by the sender, ensuring that the message recipient can confirm the source of the message and that the message has not been tampered with during transmission. This also provides proof of the integrity and source of the data, indirectly protecting user privacy. By deploying quantum-safe encryption algorithms in cloud computing and IoT environments and using the principles of quantum mechanics to protect the privacy of user data, data can be kept secure even in complex and vulnerable network environments.

[0078] The network security communication method based on the improved enhanced quantum security encryption algorithm of the present invention utilizes the improved quantum key distribution technology to transmit quantum bit sequences in the quantum channel, combines quantum entanglement states and error correction coding to generate high-quality shared quantum keys, directly increases the difficulty of eavesdropping at the physical level, improves the reliability of shared quantum key generation, and can also quickly process and correct errors at the quantum level, reduce data retransmission, and improve efficiency; quantum state tomography technology and entanglement purity test are used to ensure the security of shared quantum keys, and unsafe communication links are filtered out in time. Only shared quantum keys that pass the test will be stored, avoiding the waste of invalid computing resources and reducing the possibility of being intercepted; then, the shared quantum key is converted into a classical key through the ground state measurement of the quantum bit and the consistency check between the two parties, ensuring the correctness and confidentiality of the classical key; finally, the classical key is updated through the quantum random number hybrid protocol and the key derivation function, which enhances the dynamics and complexity of the classical key, making it difficult for potential attackers to predict and use it. The present invention has adopted strict control and protection measures in the entire process from quantum key generation, verification, conversion to storage and update, ensuring that encryption calculations can be executed efficiently even when the network data transmission volume is huge, effectively suppressing the risk of key leakage and improving the security of network communications.

[0079] In a technical solution of the present invention, a computer-readable storage medium is also provided, storing a computer program, wherein the computer program enables a computer to execute the network security communication method based on the improved enhanced quantum security encryption algorithm.

[0080] In a technical solution of the present invention, an electronic device is also provided, including: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the network security communication method based on the improved enhanced quantum security encryption algorithm is implemented.

[0081] In a technical solution of the present invention, a computer program product is also provided, including a computer program, which, when executed by a processor, implements the network security communication method based on the improved enhanced quantum security encryption algorithm.

[0082] In the embodiments disclosed in the present application, the computer storage medium can be a tangible medium that can contain or store a program for use by or in conjunction with an instruction execution system, device or equipment. The computer storage medium can include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices or equipment, or any suitable combination of the above. More specific examples of computer storage media can include electrical connections based on one or more lines, portable computer disks, hard disks, random access memories (RAM), read-only memories (ROM), erasable programmable read-only memories (EPROM or flash memory), optical fibers, portable compact disk read-only memories (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the above.

[0083] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in this application can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0084] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A network security communication method based on an improved enhanced quantum security encryption algorithm, characterized in that: The specific steps include: Step 1: During network communication, set up the quantum key pool and the classical key pool; Step 2: Before different message senders and message receivers communicate over the network, the message sender uses an improved quantum key distribution technology to send a quantum bit sequence to the message receiver through a quantum channel. The message receiver receives the quantum bit sequence and exchanges information with the message sender on a public channel to generate a shared quantum key. Step 3: Use quantum state tomography technology and quantum entanglement purity test to test the security of the shared quantum key. If it meets the security requirements, it will be stored in the quantum key pool, otherwise it will be discarded; Step 4: The message sender and the message receiver use a quantum key conversion method based on hyper-entanglement to convert the shared quantum key stored in the quantum key pool into a classical key, and regularly update the classical key and store it in the classical key pool; Step 5: During each network communication, the message sender encrypts the plaintext to be transmitted using the corresponding classic key in the classic key pool to obtain the ciphertext, and transmits the ciphertext to the message receiver; Step 6: After receiving the ciphertext, the message receiver decrypts the ciphertext using the same classic key; The specific process of converting the shared quantum key stored in the quantum key pool into a classical key in step 4 is as follows: Step 4.1: The message sender performs a ground state measurement on each quantum bit in the shared quantum key to obtain a first measurement result. The message sender sends the first measurement result to the message receiver through a secure classical communication channel, and the message receiver receives the communication result. Step 4.2, the message receiver selects a base state corresponding to the message sender, performs base state measurement on the communication result, and obtains a second measurement result; Step 4.3, determine whether the first measurement result and the second measurement result are the same, if they are the same, retain the measurement result, otherwise discard it; Step 4.4: All retained measurement results are connected in series to form a classic key; the update process of the classic key is specifically as follows: i. Use the quantum key mixing protocol combined with quantum random numbers to mix the classical key and obtain the mixed classical key K C,mixed : Where C represents the classical secret key, R1 represents the first random number generated by the quantum random number generator, and H() represents the hash function. Represents a bit-level XOR operation; ii. Update the hybrid classical key with the shared quantum key to obtain the updated classical key K C,new : K C,new =HKDF(K C,mixed ,Q) Among them, Q represents the shared quantum key, and HKDF() represents the key derivation function.

2. A network security communication method based on an improved enhanced quantum security encryption algorithm according to claim 1, characterized in that: The specific process of generating the shared quantum key in step 2 is: Q=EC(|ψ>,Cerror) Where Q represents the shared quantum key, EC() represents the error correction coding function, and |ψ> represents the high-dimensional quantum entangled state key received by the message receiver. d represents the length of the quantum bit sequence, i represents the index of d, |i> A represents the ground state information of the i-th quantum bit in the message sender, |i> B represents the ground state information of the i-th quantum bit in the message receiver, represents the symbol of tensor product, and Cerror represents the error detection result.

3. According to claim 1, a network security communication method based on an improved enhanced quantum security encryption algorithm is characterized in that: The specific process of security testing of the shared quantum key in step 3 is as follows: Among them, ρ reconstructed represents the reconstructed shared quantum key state, |ψ> represents the high-dimensional quantum entangled state key received by the message receiver, u and v both represent Pauli matrix measurements in the x, y or z direction, M uv represents the measurement matrix, P v represents the probability when v is measured under the corresponding Pauli matrix, r v Represents the correlation coefficient when v is measured under the corresponding Pauli matrix.

4. According to claim 1, a network security communication method based on an improved enhanced quantum security encryption algorithm is characterized in that: The process of obtaining the ciphertext in step 5 is: Where K represents the ciphertext, represents an encryption function that depends on the classical key in the classical key pool, M represents the plaintext to be transmitted, R2 represents the second random number generated by the quantum random number generator, Represents a bit-wise exclusive-or operation.

5. A network security communication method based on an improved enhanced quantum security encryption algorithm according to claim 4, characterized in that: The process of decrypting the ciphertext in step 6 using the same classic key is: in, Represents the third random number generated by the R3 quantum random number generator, a decryption function that depends on the classical key in the classical key pool.

6. A computer-readable storage medium storing a computer program, characterized in that: The computer program enables a computer to execute the network security communication method based on the improved enhanced quantum secure encryption algorithm as described in any one of claims 1 to 5.

7. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the network security communication method based on the improved enhanced quantum security encryption algorithm as described in any one of claims 1 to 5 is implemented.

8. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the network security communication method based on the improved enhanced quantum security encryption algorithm described in any one of claims 1 to 5 is implemented.

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