Voice encryption method for satellite mobile communication system

Abstract

The present application relates to a voice encryption method for a satellite mobile communication system in the technical field of communications. The method comprises: modifying a Tiantong terminal so that the Tiantong terminal can communicate with a cryptographic device; providing a voice encryption function only by adding an encryption and decryption driver and a cluster vocoder on a satellite mobile communication software protocol stack conforming to the Tiantong protocol standard, so as to realize the voice encryption and decryption function of a cluster service, thereby eliminating the need for changing a core network configuration; the Tiantong terminal interacting with the cryptographic device to obtain a synchronization frame, a key stream, a frame number, encryption control information, etc. required for a voice encryption and decryption process; and the Tiantong terminal interacting with the cryptographic device to obtain an encrypted voice frame number, embedding the frame number into a voice and transmitting the voice to a receiving end, and the receiving end sending the voice to the cryptographic device to obtain a decrypted voice, thereby completing encrypted communication. The voice encryption method in the present application achieves the security requirements of satellite mobile communication systems on the basis of minimal modification.

Description

Voice encryption method for satellite mobile communication system

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese Patent Application No. 202411272389.5, filed on September 11, 2024, entitled "Voice encryption method for satellite mobile communication system", which is incorporated by reference herein in its entirety. TECHNICAL FIELD

[0003] The present application relates to the field of communication technology, in particular to a voice encryption method for a satellite mobile communication system. BACKGROUND

[0004] Satellite mobile communication is a mobile communication system that uses satellites as a relay device for mobile communication signals to realize the communication between mobile users and between mobile users and fixed users. It can provide mobile voice, short message and data transmission, and video upload services for users in areas that are difficult to cover by ground communication systems. The satellite mobile communication service has the remarkable feature of providing communication services that are not limited by geographical environment and climate conditions. Satellite mobile communication services are suitable for oceans, mountains and remote areas where ground communication networks are not perfect, communication quality cannot be guaranteed, or even no service can be provided, and can provide reliable communication services for users.

[0005] However, the traditional satellite mobile communication system has a disadvantage that the information bits passing through the vocoder can be intercepted in the air, and the detected information bits can be easily decoded into the original voice.

[0006] SUMMARY

[0007] Therefore, the present application provides a voice encryption method for a satellite mobile communication system, which enables the system to meet the security requirements of group communication services without modifying the terminal hardware and core network configuration.

[0008] To achieve the above purpose, the technical solution adopted by the present application is as follows:

[0009] A voice encryption method for a satellite mobile communication system, comprising the following steps:

[0010] The processing procedure of the sending end is as follows:

[0011] (1) The sending end and the security machine interact to establish a call, i.e., call setup, and send the call type, call role and the identities of the calling and called users to the security machine. The security machine returns correct if the identification is successful, and returns error if the identification fails, which means the group call fails. In each call, the call setup is established only once, which corresponds to the call end;

[0012] (2) After the call is established successfully, the sending terminal and the security machine interact to obtain the synchronization frame. If it is the first synchronization frame interaction of the current call, the sending terminal sends a new vector to the security machine, otherwise, the sending terminal sends an old vector to the security machine. The security machine returns the synchronization frame of the current call and the size of the synchronization frame.

[0013] (3) After the sending terminal obtains the synchronization frame, the sending terminal sends the frame to the receiving terminal and obtains the calling and called user identity, and then sends the header encryption control frame to the receiving terminal.

[0014] (4) After the sending terminal receives the confirmation frame from the receiving terminal, the sending terminal enters the encrypted voice stage, interacts with the security machine to obtain the encryption key stream, the size of the key stream and the frame number, and then performs XOR operation on the clear voice and the encryption key stream to obtain the encrypted voice and sends the encrypted voice to the receiving terminal.

[0015] (5) The sending terminal ends the call and performs the call release operation with the security machine. Meanwhile, the sending terminal sends the tail encryption control frame to the receiving terminal.

[0016] The processing procedure of the receiving terminal is as follows:

[0017] (6) After the receiving terminal receives the synchronization frame and the header encryption control frame, the receiving terminal replies a confirmation frame to the sending terminal.

[0018] (7) The receiving terminal sends the synchronization frame to the security machine. After the security machine identifies the synchronization frame information, the sending terminal and the receiving terminal of the current encrypted call complete the synchronization.

[0019] (8) The receiving terminal extracts the calling and called identity from the header encryption control frame and sends the calling and called identity to the security machine to interact with the security machine.

[0020] (9) After the receiving terminal receives the encrypted voice, the receiving terminal extracts the frame number and sends the frame number to the security machine to obtain the decryption key stream, the size of the key stream and the output frame number, and then performs XOR operation on the decryption key stream and the received encrypted voice to obtain the clear voice.

[0021] (10) After the receiving terminal receives the tail encryption control frame, the receiving terminal performs the call release operation with the security machine, and the current encrypted communication ends.

[0022] Further, the size of the synchronization frame is 9 bytes, and the synchronization frame is divided into three parts, each part has 3 bytes, and the synchronization frame is transmitted three times.

[0023] Further, the sending terminal continuously sends the synchronization frame and the header encryption control frame for a set number of times. The receiving terminal replies a confirmation frame to the sending terminal as long as the receiving terminal receives the synchronization frame and the header encryption control frame once.

[0024] Compared with the prior art, the application has the following advantages:

[0025] 1. The method of the present application is rigorous, simple and compact, and easy to implement.

[0026] 2. The voice encryption method of the present application realizes the security requirements of the satellite mobile communication system with minimal changes. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly describe the present patent, one or more drawings are provided below, which are intended to assist in describing the background art, technical principles and / or certain specific embodiments of the present patent.

[0028] Figure 1 is a vocoder working principle diagram of the Tiantong terminal in the embodiment of the present application.

[0029] Figure 2 is a communication flow diagram of the encrypted voice sending end in the embodiment of the present application.

[0030] Figure 3 is a communication flow diagram of the encrypted voice receiving end in the embodiment of the present application. DETAILED DESCRIPTION

[0031] In order to facilitate those skilled in the art to understand the technical solutions of the present patent, at the same time, in order to make the technical purpose, technical solutions and beneficial effects of the present patent more clear, and make the protection scope of the claims fully supported, the technical solutions of the present patent will be further explained in the form of specific cases below.

[0032] As shown in Figure 1, a vocoder working principle diagram based on Tiantong terminal. In the present application, the support of voice encryption and decryption is mainly realized by designing and modifying the baseband protocol stack software in the Tiantong terminal. The protocol stack is composed of three protocol layers, among which SM (session management module), CC (connection management module), GMM (GPRS mobility management module) and MM (mobility management module) are the components of the NAS layer (non-access layer). RRC is the control and management of the unlimited resource layer. RLC layer and MAC layer are two key wireless communication protocol layers. PHY layer is the physical layer. The present application is based on the original protocol stack, transplants the encryption and decryption supported vocoder, and adds relevant protocol processes on the voice channel to realize the voice encryption and decryption function.

[0033] Specifically, the encrypted voice communication flow is shown in Figures 2 and 3, which is divided into sending end and receiving end, and the sending end is the one who presses the PTT key during the conversation. Due to the particularity of the group communication, this communication is in half-duplex mode, and the receiving end receives the encrypted voice sent by the sending end, while sending the FREE frame without passing through the vocoder to maintain the link.

[0034] A voice encryption method for a satellite mobile communication system, specifically comprising the following steps:

[0035] As shown in Figure 2, the processing process of the sending end is:

[0036] (1) After the terminal is successfully registered in the network, voice service is performed; the sending terminal presses the PTT key, and the sending terminal and the security machine perform call setup interaction, i.e., callsetup, to send the call type, call role and main and called user identity to the security machine, and the security machine returns correct if the recognition is successful; if the recognition fails, an error is returned, and the group call fails this time; in each call, call setup is established only once, which is echoed by call end.

[0037] (2) After the call setup is successful, the sending terminal and the security machine perform synchronization frame acquisition interaction; if it is the first synchronization frame interaction of this call, the sending terminal sends a new vector to the security machine, otherwise an old vector is sent to the security machine; the security machine returns the synchronization frame of this call and the synchronization frame size; in the communication system, due to the limitation of channel bandwidth, voice service data cannot be directly transmitted on the channel, and a vocoder needs to be used to compress the original voice data of the user to a specified code rate, so as to be transmitted on a relatively narrow channel. In the Tianhong No. 1 satellite mobile communication + system, the circuit domain voice dedicated channel of the terminal is divided into three rates of 4 kbps / 2.4 kbps / 1.2 kbps, so the number of bits that can be transmitted per 60 ms is: 2.4 kbps*60 ms, i.e., 144 bits, 18 bytes. The synchronization frame size is 9 bytes, in order to prevent misjudgment of synchronization frame transmission and reception, the synchronization frame is divided into three parts, each part is 3 bytes, and is transmitted three times. Every 60 ms includes 2 bytes of frame header 0xEB 0x90, 3 bytes of PI (synchronization frame), and 1 byte of check frame. The calculation method of the last byte of the check frame is that B0+B1+B2+B3+B4+B5=0, i.e., the least significant byte of the sum of the six bytes is 0, B0-B5 represents the first to the sixth byte. The structure is shown in Table 1. The transmission of LCH (header encryption control frame), LCT (tail encryption control frame), FREE (blank frame) and CONFIRM (confirmation frame) is also the same structure. Every 60 ms includes 2 bytes of frame header 0xEB 0x90, 3 bytes of content frame, and 1 byte of check frame.

[0038] Table 1 Frame structure

[0039] (3) After the sending terminal acquires the synchronization frame, it sends the frame to the receiving terminal, and acquires the main and called user identity to form a header encryption control frame and send it to the receiving terminal; the main and called identity is 3 bytes, which is divided into 3 frames according to the structure of Table 1 and transmitted to the receiving terminal through the air interface.

[0040] (4) After the sending end receives the confirmation frame, it enters the encrypted voice stage. If the receiving end has not received the synchronization frame and the header encryption control frame, the sending end will insert the synchronization frame and the header encryption control frame once after sending 500 voice frames, until it receives the confirmation frame from the receiving end.

[0041] After entering the encrypted voice stage, the sending end interacts with the security machine to obtain the encryption key stream, the key stream size and the frame number. Then, the clear voice is XORed with the key stream to obtain the initial encrypted voice. According to the foregoing description, the vocoder that can be used for encryption and decryption functions is 2.2 kbps, and the channel can carry a rate of 2.4 kbps. The extra 12 bits per 60 ms can be used to send the frame number information. The vocoder data format is shown in Table 2, and the vocoder bit appropriation scheme is shown in Table 3.

[0042] Table 2 Vocoder data format

[0043] Table 3 Vocoder bit appropriation scheme

[0044] (5) The sending end ends the call and releases the PTT key, and performs a call release operation with the security machine. At the same time, the tail encryption control frame is sent to the receiving end according to the structure of Table 1.

[0045] The processing process of the receiving end is as follows:

[0046] (6) After the receiving end receives the synchronization frame and the header encryption control frame, it replies to the sending end with a confirmation frame. In order to prevent the receiving end from receiving the synchronization frame and the encryption control information frame incorrectly or missing, the sending end continuously sends the synchronization frame and the header encryption control frame three times. The receiving end replies to the sending end with a confirmation frame as long as it receives the synchronization frame and the header encryption control frame once.

[0047] (7) After the receiving end receives the synchronization frame, the synchronization information is sent to the security machine. The security machine identifies the synchronization frame information, indicating that the sending end and the receiving end of the encrypted call have been synchronized.

[0048] (8) The receiving end extracts the main called identity from the header encryption control frame and sends it to the security machine for call establishment interaction.

[0049] (9) After the receiving end receives the encrypted voice, it first extracts the frame number from the 12 bits, and then sends the frame number to the security machine to obtain the decryption key stream, the key stream size and the output frame number. The decryption key stream is XORed with the received encrypted voice to obtain the clear voice.

[0050] (9) After the receiving end receives the tail encryption control frame, it performs a call release operation with the security machine, and the encrypted communication ends.

[0051] It should be understood that the above detailed description and specific examples, while indicating preferred embodiments of the application, are given by way of illustration only, and are not by way of limitation. Any modifications, equivalent replacements, improvements, etc. made without departing from the scope of the application should be included in the protection scope of the application.

Claims

1. A voice encryption method for a satellite mobile communication system, comprising the following steps: The processing procedure of the sending end is as follows: (1) The sending end and the security machine interact to establish a call, i.e. call setup, and send the call type, call role and the identities of the calling and called users to the security machine. The security machine returns correct if the recognition is successful, and returns error if the recognition fails, and the group call fails this time; The call setup is established only once in each call, which corresponds to the call end; (2) After the call setup is successful, the sending end and the security machine interact to obtain the synchronization frame. If it is the first synchronization frame interaction in this call, the sending end sends a new vector to the security machine, otherwise, an old vector is sent to the security machine; The security machine returns the synchronization frame and the size of the synchronization frame in this call; (3) The sending end obtains the synchronization frame, frames it and sends it to the receiving end, and obtains the identities of the calling and called users to form a header encryption control frame and send it to the receiving end; (4) After the sending end receives the confirmation frame from the receiving end, it enters the encrypted voice stage, interacts with the security machine to obtain the encryption key stream, the size of the key stream and the frame number, then performs XOR operation on the clear voice and the encryption key stream to obtain the cipher voice and send it to the receiving end; (5) The sending end ends the call and performs call release operation with the security machine, and sends a tail encryption control frame to the receiving end; The processing procedure of the receiving end is as follows: (6) After the receiving end receives the synchronization frame and the header encryption control frame, it replies a confirmation frame to the sending end; (7) The receiving end sends the synchronization frame to the security machine, and the sending end and the receiving end complete synchronization after the security machine recognizes the synchronization frame information in this call; (8) The receiving end extracts the identities of the calling and called users from the header encryption control frame and sends them to the security machine to interact to establish a call; (9) After the receiving end receives the cipher voice, it extracts the frame number and sends it to the security machine to obtain the decryption key stream, the size of the key stream and the output frame number, then performs XOR operation on the decryption key stream and the received cipher voice to obtain the clear voice; (10) After the receiving end receives the tail encryption control frame, it performs call release operation with the security machine, and the encrypted communication ends.

2. A voice encryption method for a satellite mobile communication system according to claim 1, wherein The size of the synchronization frame is 9 bytes, and the synchronization frame is divided into three parts, each part being 3 bytes, and transmitted three times.

3. A voice encryption method for a satellite mobile communication system according to claim 1, wherein The sending end continuously sends the synchronization frame and the header encryption control frame for a set number of times, and the receiving end replies a confirmation frame to the sending end as long as it receives the synchronization frame and the header encryption control frame once.

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