CN104135727B - A kind of wireless body area network safe transmission method - Google Patents

Abstract

The invention discloses a wireless body area network security transmission method, which includes the following stages: 1. System initialization: the system uses the clock progress frequency of the node and the clock offset of the two nodes to exchange two adjacent nodes and the relationship between the node and the Sink node. 2. Formation of secure routing: When all nodes receive the "OK" message, each node deletes the original AODV routing information, and uses the improved AODV protocol to form a secure routing 3. Data encrypted transmission: the data packet is divided into two parts: routing information Data1 and perception data Data2, which are encrypted with two different pairwise keys respectively. Two adjacent nodes verify Data1 with each other, and sink nodes verify Data2. , and then transfer. This solution supports "plug and play" and can guarantee BAN data security and privacy, and is applicable to all BAN networks.

Description

A wireless body area network security transmission method

technical field

The invention relates to the field of wireless network encryption transmission, in particular to a wireless body area network security transmission method without prior pre-installed keys.

Background technique

Wireless body area network BAN (Body Area Network) is a network that is worn on the body of the ward to monitor human physiological and medical data. Its sensor nodes transmit the perceived data to the Sink of the BAN through one or more hops. Node, which can further transmit data to PC or PDA, provide real-time monitoring of physiological data for the wards (the elderly, infants, athletes, disabled and chronically ill), and is also widely used in consumer electronics, entertainment, sports, environment Intelligent, animal husbandry, military or security and other fields. Although BAN is a branch of WSN (Wireless Sensor Network, Wireless Sensor Network), it has many similarities with WSN; however, BAN is different from general WSN in terms of deployment method, node type and scale, traffic type, delay, mobility, etc., especially Yes, WSNs are often assumed to operate in unattended conditions, while BANs operate in an attended environment (the ward himself, medical staff or family).

Since the physiological and medical data of the ward sensed by the sensor nodes in BAN play a very important role in medical diagnosis and treatment, and also involve the personal privacy of the ward, data security and privacy are one of the BAN network At the same time, the safety measures for clinical applications hope that "plug and play" simple operation. Information encryption and node authentication are the main measures to ensure network security communication, and key management is the key to ensure information confidentiality, integrity and prevent illegal node intrusion. In the general sensor network, there are mainly two kinds of pre-installed symmetric key and asymmetric public key technology to ensure data security, but these are not suitable for BAN network.

Pre-installed symmetric key technology: Due to the small scale of BAN nodes (generally N is less than 50), each node can pre-install N-1 keys to ensure encrypted data transmission between any two nodes. This seems feasible on the surface, but there are The following questions:

(1) Each BAN must be pre-installed with N-1 keys different from other BANs, otherwise, when two patients wearing BANs approach each other, a paired key may be formed between the nodes of the two BANs, resulting in wrong transmission;

(2) Since the BAN nodes are heterogeneous and may come from different manufacturers, it is very difficult for end users (medical staff or patients) to assign N-1 keys to each node in the BAN. They prefer to "namely The simple operation of "Plug-And-Play", that is, any form of Key distribution and management process in BSN should be minimized, automated and transparent to users;

(3) Even if the N-1 keys are pre-installed after hard work, it is very difficult to change the pre-installed N-1 keys in the clinic when the keys are found to be leaked after the BAN works.

Asymmetric public key technology: This technology mainly has the following problems:

(1) The energy and computational overhead are not suitable for resource-constrained sensor nodes;

(2) The dependence on the environment and the complexity of operation limit the clinical application.

At present, in BAN, human physiological information and wireless channel properties are mainly used to generate symmetric key encryption data, and the "plug and play" effect is obtained without sharing the key in advance, but both have shortcomings :

1. Using human physiological information

Since the BSN network is used to monitor human physiological information, physiological information is not easy to imitate. Many studies use electroencephalogram (EEG), photoplethysmogram (PPG), electrocardiogram (ECG) and other physiological information to establish secret channels to authenticate nodes and information. However, this requires all nodes to have the ability to perceive the same signal (EEG or ECG, etc.), which puts forward new requirements for node hardware; It is difficult to have the same accuracy, which means that the accuracy of key recovery cannot be guaranteed to be 100%.

2. Utilize the physical properties of nodes and wireless channels

It is a relatively new direction to use the channel characteristics of the BAN/BSN network and the physical properties of the nodes themselves to generate symmetric keys. The physical properties that are relatively easy to obtain mainly include Signal Strength, which solves the problem caused by the use of human physiological information. Key recovery accuracy cannot be guaranteed 100% of the problem. However, since most wireless sensor nodes use half-duplex communication, the measurement of RSS cannot be carried out in two directions simultaneously, and the key generation between two nodes needs to go through sampling, quantization, reconcile, and privacy of wireless signals. Amplification (Privacy Amplification) four stages, which brings about the low efficiency of key extraction.

The State Intellectual Property Office of the People's Republic of China published a patent document with the application publication number CN102624530A on August 1, 2012. The name is a certificateless remote anonymous authentication method for wireless body area network, which is realized by the method of public key/private key cooperation. Data encryption has the problems of low accuracy and low extraction efficiency.

Contents of the invention

The present invention mainly solves the technical problems existing in the prior art that the plug-and-play feature, accuracy, and extraction efficiency cannot be taken into account, and provides a method that does not require pre-installed keys in advance, and uses traditional The idea and method of encrypting data with the paired key of the sense node and the sink node and encrypting the routing information with the paired key of two adjacent nodes supports "plug and play", making it possible to ensure the complex theory of BAN data security and privacy A secure transmission method for wireless body area networks that becomes operable and practical with technical issues.

The present invention mainly solves the above technical problems through the following technical solutions: a wireless body area network secure transmission method, including the following stages:

(1) System initialization: the system uses the clock progress frequency of the node and the dynamics and uniqueness of the clock offset of the two nodes, under the control of the standard time of the sink node, the clock progress of two adjacent nodes and between the node and the sink node is exchanged frequency, forming two types of pairwise keys;

(2) Secure routing formation: After all nodes receive the "OK" message, each node deletes the original AODV (Ad hocon-demand distance vector routing) routing information, and adopts the improved AODV protocol to form secure routing and encrypt transmission data;

(3) Data encrypted transmission: Divide the data packet into two parts: routing information Data1 and perception data Data2, which are encrypted with two different pairwise keys respectively. Two adjacent nodes verify Data1 with each other, sink nodes verify Data2, and then transmit .

As a preference, if CF _x ( t ) represents the time of node x at real time t , the clock progress frequency CF _x ′ ( t ) is defined as:

CF _x ′ ( t ) = dCF _x ( t )/ dt ( t >=0) (1)

The time of the Sink node is used as the real time, and the clock progress frequency of the real time is equal to 1;

The clock offset CS ₁₂ ( t ) of node 1 and node 2 is defined as the difference between CF ₁ ′ ( t ) and CF ₂ ′ ( t ):

CS ₁₂ ( t ) = CF ₁ ′ ( t )- CF ₂ ′ ( t ) (2)

The ID of node x is recorded as ID _x ;

The specific operation of system initialization is as follows:

(1) The Sink node broadcasts two randomly spaced standard time stamps T ₁ and T ₂ to all nodes in the wireless body area network in a single-hop manner;

(2) After receiving T ₁ and T ₂ , node x uses the formula (1) to calculate its own clock progress frequency as:

CF _x ′ ( T ₂ - T ₁ )=( CF _x ( T ₂ )- CF _x ( T ₁ ))/( T ₂ - T ₁ )

Node x saves CF _x ′ ( T ₂ - T ₁ ), and sends CF _x ′ ( T ₂ - T ₁ ) + ID _x to the Sink node through the original AODV protocol. When the wireless body area network is working, node x uses K _x encrypts the perceived data, and K _x is defined as follows:

K _x = F ( CF _x ′ ( T ₂ - T ₁ ), ID _x ) (3)

Here F is a key generation function, which generates a key of a specified length as required, but the key must satisfy certain mathematical characteristics. For example, if the length of ID _x is 1 byte, and CF _x ′ ( T ₂ - T ₁ ) is 4 bytes, a 64-bit key needs to be generated according to the value of ID _x and CF _x ′ ( T ₂ - T ₁ ) Different, inserting 3 bytes meets the mathematical characteristics; for example, a Hash function can be used to generate a key;

(3) When node x sends CF _x ′ ( T ₂ - T ₁ )+ ID _x to the sink node, the neighbor nodes within one hop of x will also receive the information and save it in its own storage; similarly, x As a neighbor node, it will also receive the clock progress frequency and ID information of other nodes, so that the two nodes in the BAN complete the clock progress frequency exchange;

(4) On the path from node x to sink node, two adjacent nodes m and n have the clock progress frequency of the other, and their clock offset and the key K _mn or K _nm generated by the IDs of the two nodes are unique, It is used to encrypt routing information, two nodes perform mutual authentication, K _mn or K _nm are the same, defined as follows:

K _mn = K _nm = F ( CS _mn ( T ₂ - T ₁ ), ID _m , ID _n ) (4)

CS _mn ( T ₂ - T ₁ ) =ABS( CF _m ′ ( T ₂ - T ₁ )- CF _n ′ ( T ₂ - T ₁ ))

Here F is the key generation function, which is the same as formula (3), and ABS is the absolute value;

(5) After the sink node receives the clock progress frequency and ID information of all nodes, the sink node forms a pairwise key K _x with each node x , which is used to encrypt the data itself, and two adjacent nodes m and n form a The pairwise key K _mn or K _nm is used to encrypt routing information; when the Sink node broadcasts "OK" information in a single-hop manner, BAN enters the stage of secure route formation and data encryption transmission.

As a preference, when all nodes receive the "OK" message, each node deletes the original AODV routing information, adopts the improved AODV protocol to form a secure route and encrypts the transmitted data; the improved AODV protocol message is to add a clock on the basis of the original message Progress frequency field CF; when node x wants to send data to the sink node, it must first send a RREQ (routing request) message to form a safe route to the sink node, and then transmit data according to the route, and the data source node x requests to form a sink node The safe routing operation is as follows:

(1) Node x generates a RREQ message, fills in each field information like the original AODV, and fills the added CF field with CF _x ′ ( T ₂ - T ₁ ) of node x , and then broadcasts to neighbor nodes;

(2) When the neighbor node m of node x receives the RREQ message, the operation is divided into three cases as follows:

A. If the CF field in the RREQ message is empty, it means that the RREQ comes from an untrusted node, and stop forwarding the message;

B. If the CF field in the RREQ message exists and the CF value CF _x ′ ( T ₂ - T ₁ ) of the node x is saved in the node m , the node m compares whether the two values are equal, and if they are equal, the node m uses its own The CF value CF _m ′ ( T ₂ - T ₁ ) replaces the CF value of node x in the RREQ message, and continues to forward the RREQ; otherwise, stop forwarding;

C. If the CF field in the RREQ message exists and node m does not save the CF value of node x , node m will request the CF value of node x from the sink node. If the sink node has the CF value of node x , it will CF _x ′ ( T ₂ - T ₁ ) is encrypted with K _m and then sent to node m in a single hop. After receiving the message and decrypting it correctly with K _m , node m saves CF _x ′ ( T ₂ - T ₁ ) in the memory. The operation is the same as B;

(3) After the neighbor node of node m receives the RREQ message, it forwards the RREQ message in a similar manner to step (2);

(4) When the sink node receives the RREQ message, it generates a RREP (routing response) message, fills the CF field of the RREP with the CF value of the sink node, and then unicasts it back to the neighbor node of the sink node;

(5) When the neighbor node of the Sink node receives the RREP message, it returns the RREP message similarly to step (2);

(6) When the data source node x receives the RREP message, it forms a safe route that only legal nodes participate in.

Preferably, N1, N2, and N3 are all nodes, assuming that the safe route from N1 to Sink is N1->N2->N3->Sink, and the source node N1 generates a data packet composed of tags Tag, Data1 and Data2; Tag is a message Type, Data1 contains source ID, target ID and data generation time information, Data2 is the data actually perceived by N1; in encrypted data transmission, nodes N1, N2, N3 and Sink operate as follows:

(1) N1: Encrypt Data2 with the pairwise key K ₁ known only to N1 and the Sink node to obtain E ( Data2 , K ₁ ), and encrypt Data1 with the pairwise key K ₁₂ known only to nodes N1 and N2 to E ( Data1 , K ₁₂ ), and then unicast the data packet to N2;

(2) N2: first use K ₁₂ to decrypt Data1, that is, D ( E ( Data 1, K ₁₂ ), K ₁₂ ) to get Data1, and then use the paired key K ₂₃ known only to nodes N2 and N3 to obtain routing information Encrypt as E ( Data1 , K ₂₃ ), and then send the data packet to N3; E is the encryption operation, D is the decryption operation;

(3) N3: first use K ₂₃ to decrypt Data1, that is, D ( E ( Data 1, K ₂₃ ), K ₂₃ ) to get Data1, and then use the paired key K known only by node N3 and Sink node after obtaining routing information ₃₀ is encrypted as E ( Data 1, K ₃₀ ), and then the data packet is sent to the Sink node;

(4) Sink: first use K ₃₀ to decrypt Data1, that is, D ( E ( Data 1, K ₃₀ ), K ₃₀ ) to get Data1, after obtaining the source node information, use K ₁ to decrypt Data2, that is, D ( E ( Data 2, K ₁ ), K ₁ ) to obtain real data Data2.

Encryption and decryption can be processed using conventional algorithms, such as the AES algorithm.

The substantive effect brought by the present invention is that under the premise of ensuring security, it satisfies the plug-and-play feature, does not need to set the key through a complicated process, has good key recovery accuracy, and does not exist The problem of low key extraction efficiency.

Description of drawings

Fig. 1 is a kind of general BAN structural representation of the present invention;

Fig. 2 is a kind of improved AODV protocol message structure schematic diagram of the present invention;

Fig. 3 is a schematic diagram of an encryption and transmission process of the present invention.

detailed description

The technical solutions of the present invention will be further specifically described below through the embodiments and in conjunction with the accompanying drawings.

Embodiment: In this embodiment, a wireless body area network BAN (Body Area Networks) secure transmission method that does not require pre-installed keys is divided into three stages:

(1) System initialization: System initialization needs to be carried out in a safe environment, using the clock progress frequency of the node (microsecond level), the dynamics and uniqueness of the clock offset Clock Skew of the two nodes, under the control of the Sink standard time, exchange Two adjacent nodes and the clock progress frequency between the node and the Sink form two types of pairwise keys (Pairwise Key);

(2) Formation of secure routing: Through the improvement of the well-known reactive protocol AODV, a secure routing that only legal nodes participate in is formed;

(3) Divide the data packet into two parts, the routing information Data1 and the sensing data Data2, which are encrypted with two different pairwise keys respectively. The two adjacent nodes verify Data1 and the Sink node verifies Data2, which improves the encryption and decryption. Efficiency, but also to ensure data security and privacy.

1. System model

1 Network model

The general BAN structure of the present invention is shown in Figure 1, the square node in the figure is the Sink node (ID=0), assuming:

(1) There are N sensor nodes {S ₁ , S ₂ ,...,S _N } deployed on the ward (generally N <50 in BAN), each node has a unique ID (greater than 0), The nodes are not related to each other (each node can independently determine the perceived data), equipped with the same wireless communication interface, such as ZigBee;

(2) There is 1 Sink node, whose ID=0, collects the data perceived by all sensor nodes, which is safe in itself, and knows the node ID in the current running BAN and the frequency interval of data generated by each node;

(3) The Sink node has enough power to transmit data to all sensor nodes in a one-hop or multi-hop manner. The sensor node uses very low power short-distance transmission (good for the human body) Transmit the perceived data to the Sink node, and the transmission protocol uses AODV;

(4) The BAN network has adopted a certain time synchronization mechanism, but it is different at the PPM level, and its synchronization itself is safe;

(5) When the BAN is initialized or new nodes are added and reset, there are no malicious nodes around (operated by medical staff or guardians, which can be guaranteed in an indoor environment), and this assumption is often made in general WSNs;

2 attack model

The present invention mainly considers the confidentiality and integrity of data, and the attack model is assumed to be:

(1) Within the wireless communication range, the attacker can eavesdrop on the data sent by each node in the BAN at will, and after modification or delay, it can continue to propagate to the BAN with various powers;

(2) The attacker can impersonate other legal nodes and publish forged data to the BAN network;

(3) The attacker can carry out node capture attack.

2. Protocol description

1 Clock progress frequency and clock offset

If CF _x ( t ) represents the time of node x at real time t , the clock progress frequency (abbreviated as CF) CF _x ′ ( t ) is defined as:

CF _x ′ ( t ) = dCF _x ( t )/ dt ( t >=0) (1)

The time of the Sink node is used as the real time, and the clock progress frequency of the real time is equal to 1;

The clock offset CS ₁₂ ( t ) of node 1 and node 2 is defined as the difference between CF ₁ ′ ( t ) and CF ₂ ′ ( t ):

CS ₁₂ ( t ) = CF ₁ ′ ( t )- CF ₂ ′ ( t ) (2)

The ID of node x is recorded as ID _x ;

In general, modern processor digital clocks have the following two properties:

1. The clock skew of any clock is stable at normal temperature;

2. Each stable clock offset can be considered unique.

2 System initialization

In a safe environment, when the BAN is powered on or reset (system initialization), each node clears the original clock progress frequency and routing information stored in the memory, and uses the unimproved AODV to transmit data. The operation is as follows:

(1) The Sink node broadcasts two randomly spaced standard time stamps T ₁ and T ₂ to all nodes in the wireless body area network in a single-hop manner;

(2) After receiving T ₁ and T ₂ , node x uses the formula (1) to calculate its own clock progress frequency as:

CF _x ′ ( T ₂ - T ₁ )=( CF _x ( T ₂ )- CF _x ( T ₁ ))/( T ₂ - T ₁ )

Node x saves CF _x ′ ( T ₂ - T ₁ ), and sends CF _x ′ ( T ₂ - T ₁ ) + ID _x to the Sink node through the original AODV protocol. When the wireless body area network is working, node x uses K _x encrypts the perceived data, and K _x is defined as follows:

K _x = F ( CF _x ′ ( T ₂ - T ₁ ), ID _x ) (3)

Here F is a key generation function, which generates a key of a specified length as needed;

(3) When node x sends CF _x ′ ( T ₂ - T ₁ )+ ID _x to the sink node, the neighbor nodes within one hop of x will also receive the information and save it in its own storage; similarly, x As a neighbor node, it will also receive the clock progress frequency and ID information of other nodes, so that the two nodes in the BAN complete the clock progress frequency exchange;

(4) On the path from node x to sink node, two adjacent nodes m and n have the clock progress frequency of the other, and their clock offset and the key K _mn or K _nm generated by the IDs of the two nodes are unique, It is used to encrypt routing information, two nodes perform mutual authentication, K _mn or K _nm are the same, defined as follows:

K _mn = K _nm = F ( CS _mn ( T ₂ - T ₁ ), ID _m , ID _n ) (4)

CS _mn ( T ₂ - T ₁ ) =ABS( CF _m ′ ( T ₂ - T ₁ )- CF _n ′ ( T ₂ - T ₁ ))

Here F is the key generation function, which is the same as formula (3), and ABS is the absolute value;

(5) After the sink node receives the clock progress frequency and ID information of all nodes, the sink node forms a pairwise key K _x with each node x , which is used to encrypt the data itself, and two adjacent nodes m and n form a The pairwise key K _mn or K _nm is used to encrypt routing information; when the Sink node broadcasts "OK" information in a single-hop manner, BAN enters the stage of secure route formation and data encryption transmission.

3 Safe route formation

When all nodes receive the "OK" message, each node deletes the original AODV routing information, and uses the improved AODV protocol to form a secure route and encrypt data for transmission. The improved AODV protocol message is to add a clock progress frequency field CF on the basis of the original message, as shown in Figure 2; the method of forming the route is similar to the original AODV, but the CF verification process is added. When node x wants to send data to the sink node, it must first send a RREQ request to form a secure route to the sink, and then transmit data according to the route. The data source node x requests to form a secure route to the sink as follows:

(1) Node x generates a RREQ message, fills in each field information like the original AODV, and fills the added CF field with CF _x ′ ( T ₂ - T ₁ ) of node x , and then broadcasts to neighbor nodes;

(2) When the neighbor node m of node x receives the RREQ message, the operation is divided into three cases as follows:

A. If the CF field in the RREQ message is empty, it means that the RREQ comes from an untrusted node, and stop forwarding the message;

B. If the CF field in the RREQ message exists and the CF value CF _x ′ ( T ₂ - T ₁ ) of the node x is saved in the node m , the node m compares whether the two values are equal, and if they are equal, the node m uses its own The CF value CF _m ′ ( T ₂ - T ₁ ) replaces the CF value of node x in the RREQ message, and continues to forward the RREQ; otherwise, stop forwarding (indicating that the RREQ may come from a fake node);

C. If the CF field in the RREQ message exists and the CF value of node x is not saved in node m , it may be the result of changes in the network topology due to human body movement or different postures. Node m requests the CF value of node x from the Sink node. If the Sink node has the CF value of node x , it encrypts CF _x ′ ( T ₂ - T ₁ ) with K _m and sends it to node m in a single-hop manner. Node m After receiving the message and correctly decrypting it with K m , _m saves CF _x ′ ( T ₂ - T ₁ ) in the memory, and the subsequent operation is the same as that of B;

(3) After the neighbor node of node m receives the RREQ message, it forwards the RREQ message in a similar manner to step (2);

(4) When the sink node receives the RREQ message, it generates a RREP message, fills the CF field of the RREP with the CF value of the sink node (equal to 1), and then unicasts it back to the neighbor node of the sink node;

(5) When the neighbor node of the Sink node receives the RREP message, it returns the RREP message similarly to step (2);

(6) When the data source node x receives the RREP message, it forms a secure route that only legal nodes participate in.

4 Encrypted data transmission

After the secure route is formed, the data source node can transmit data to the sink, and its encryption and transmission process is shown in Figure 3.

In Figure 3, N1, N2, and N3 are all nodes. Assume that the safe route from N1 to Sink is N1->N2->N3->Sink, and the source node N1 generates a data packet composed of tags Tag, Data1, and Data2; Tag It is a message type, Data1 contains source ID, target ID and data generation time information, and Data2 is the data actually perceived by N1; in encrypted data transmission, nodes N1, N2, N3 and Sink operate as follows:

(1) N1: Encrypt Data2 with the paired key K ₁ known only to N1 and Sink nodes to obtain E ( Data2 , K ₁ ), and encrypt Data1 with the paired key K ₁₂ known only to nodes N1 and N2 to E ( Data1 , K ₁₂ ), and then unicast the data packet to N2;

(2) N2: first use K ₁₂ to decrypt Data1, that is, D ( E ( Data 1, K ₁₂ ), K ₁₂ ) to get Data1, obtain the routing information and then encrypt it with the pairwise key K ₂₃ that only nodes N2 and N3 know is E ( Data1 , K ₂₃ ), and then transmits the data packet to N3; E is an encryption operation, and D is a decryption operation;

(3) N3: first use K ₂₃ to decrypt Data1, that is, D ( E ( Data 1, K ₂₃ ), K ₂₃ ) to get Data1, and then use the paired key K known only by node N3 and Sink node after obtaining routing information ₃₀ Encrypt Data1, namely E ( Data 1, K ₃₀ ), and then transmit the data packet to the Sink node;

(4) Sink: first use K ₃₀ to decrypt Data1, that is, D ( E ( Data 1, K ₃₀ ), K ₃₀ ) to get Data1, and after obtaining the source node information, use K ₁ to decrypt Data2, that is, D ( E ( Data 2, K ₁ ), K ₁ ) to obtain real data Data2.

5 Security Analysis

The following analyzes the security of our invention from the aspects of key dynamics and accuracy, passive and active attacks, node capture, new node joining, and "plug and play":

(1) Key dynamics and accuracy: The two keys generated each time initialization are dynamic. This is because the standard time interval broadcast by the Sink node is random, and CF changes with the ambient temperature. The key calculation formula (3) and (4) are bound with the node ID (unique), so the two keys are unique;

The present invention does not bring about the accuracy problem of using physiological information to generate symmetric key recovery, and does not have the low efficiency problem of extracting the key from the physical properties of the wireless channel; this is because the CF is calculated by the node itself, and does not need a node to measure For the CF of another node, two adjacent nodes complete the CF value exchange in a secure environment without key extraction process.

(2) Passive attack: The eavesdropping node can approach the BAN infinitely, and eavesdrop on the data sent by each node in the BAN; since the node data packet is divided into two parts, which are encrypted with two different pairwise keys, the security routing The legal node only knows which node the data comes from, and does not know the content of the data; even if the eavesdropper knows the key generation function F , he does not know which node sent the eavesdropped information, nor which neighbor node received it, and the eavesdropper It is very difficult for the reader to analyze the key K _mn , and K _x is closely related to the ID of x , so it is difficult to obtain the real Data2.

(3) Active attack

Analyze the three main manifestations of active attacks:

Replay: It only makes sense for an attacker to replay outdated data. Assume that the attacker impersonates node x to broadcast outdated data (without any modification, just delayed forwarding), only x ’s neighbor node i can correctly decrypt E ( Data1 , K _xi ), obtain routing information, and forward it to i ’s neighbor node, other The node stopped forwarding because it could not decrypt E ( Data1 , K _xi ) correctly; however, the time of the entire BAN network is synchronized, and node x can use a time domain value to judge whether the data packet is out of date, even if the data is transmitted to the Sink within the domain value time node, the Sink node will also compare the data with the last data of the node and discard the outdated data and give an alarm;

Counterfeiting: Counterfeiting means that the attacker fakes the legal node ID and sends fake data to the Sink node. Assuming that the counterfeit node is powerful enough, all legitimate nodes in BAN/BSN can receive the messages sent by the counterfeit node. If the fake node is a new node, a secure route must be formed before sending data. Since the formation of a secure route requires node authentication, all legitimate nodes (including Sink) do not have the CF information of the fake node, and routing information cannot be established. Forged information is sent to the Sink node; if a legitimate node x is faked to send fake data, the attacker must provide the CF information of x to the neighbor node i of x ; the attacker cannot form a route because he does not have this data, so he cannot send the fake legal node Transfer data to Sink.

Tampering: Tampering is replaying after modifying the data, that is, the attacker modifies Data2 (Data1 is not modified), and sends the data packet of the legal node x again; the legal nodes adjacent to x all receive the forged information, but The route formed by AODV is unicast transmission, and the nodes that are not on the route from x to Sink will ignore the forged information, and the neighbor node i (first hop node) of x on the routing table uses the key between the legitimate node x K _xi decrypts E ( Data1 , K _xi ) (the intermediate node does not verify Data2), no error is found, the data can be sent to the sink node, but the sink node cannot use K _x to decrypt E ( Data 2, K _x ), so the data is discarded And call the police.

(4) Node capture

Assuming that the node is captured (lost or otherwise), the legitimate node becomes a malicious node and returns to the original BAN after leaving the guardian for a period of time; during this time, the attacker can obtain the CF in the legitimate node and the CF of its neighbor nodes , which can be generated by the key generation function Two pairwise keys are calculated, that is, BAN does not have any secrets at all, and the attack model also takes this into account. Since BAN is a manned network with heterogeneous nodes and no redundant nodes, when a node is lost, firstly the Sink can detect a node failure or loss within a certain time range (the interval between nodes generating data) and alarm; secondly, even if the node is found to capture Attacks (patients and medical staff are more likely to find that the node is lost or replaced), after clearing the malicious contacts, only need to re-power on and reset in a safe environment, Sink broadcasts new T ₁ and T ₂ , when the malicious node enters the BAN again, because The CF information generated last time is no longer used, and passive and active attacks cannot be carried out.

(5) New node joining and "plug and play"

When it is necessary to add a new sensor node to the original BAN, it is only necessary to perform a power-on reset after installing the new node on the ward in a safe environment; internally, it is to re-initialize the system (key generation ), secure route formation, and encrypted data transmission; from the outside, the power-on reset itself is a button operation, which is operable for medical staff and family guardians, and does not require special professional knowledge, thus satisfying the "plug and play" use".

The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which the present invention belongs can make various modifications or supplements to the described specific embodiments or adopt similar methods to replace them, but they will not deviate from the spirit of the present invention or go beyond the definition of the appended claims range.

Although terms such as node, progression frequency, and offset are frequently used in this paper, the possibility of using other terms is not excluded. These terms are used only for the purpose of describing and explaining the essence of the present invention more conveniently; interpreting them as any kind of additional limitation is against the spirit of the present invention.

Claims (2)

1. a kind of wireless body area network safe transmission method, it is characterised in that including with the next stage：

（1）System initialization：System using node clock progress frequency and two nodes clock skew dynamic with only One property, in the case where the Sink node standard time controls, the clock exchanged between two adjacent nodes and node and Sink node enters spread spectrum Rate, forms two kinds of pairwise key；

（2）Security routing is formed：After all nodes receive " OK " information, each original AODV routing iinformations of knot removal are adopted With improved AODV agreements formation Security routing and encrypted transmission data；

（3）Data Encryption Transmission：Packet is divided into routing iinformation Data1 and perception data Data2 two parts, respectively with two kinds Different pairwise key encryptions, two adjacent nodes verify mutually Data1, Sink node checking Data2, are then transmitted；

IfCF _x (t) represent nodexIn actual timetTime, clock progress frequencyCF _x ′(t) be defined as：

CF _x ′(t)=dCF _x (t)/dt (t>=0) （1）

The time of Sink node is equal to 1 as actual time, the clock progress frequency of actual time；

The clock skew of node 1 and node 2CS ₁₂ (t) be defined asCF ₁ ′(t) andCF ₂ ′(t) difference：

CS ₁₂ (t)= CF ₁ ′(t)- CF ₂ ′(t) （2）

Node x ID is designated asID _x ；

System initialization concrete operations are：

（First 1）Sink node is with the standard time of single-hop mode all two random intervals of node broadcasts into wireless body area network StampT ₁ WithT ₂ ；

（First 2）NodexReceiveT ₁ WithT ₂ Afterwards, formula is used（1）Calculate oneself clock progress frequency be：

CF _x ′(T ₂ -T ₁ )=(CF _x (T ₂ )- CF _x (T ₁ ))/( T ₂ -T ₁ )

NodexPreserveCF _x ′(T ₂ -T ₁ ), and willCF _x ′(T ₂ -T ₁ )+ID _x Sink node is sent to by original AODV agreements, when When wireless body area network works, nodexWithK _x Data to perception are encrypted,K _x It is defined as follows：

K _x =F(CF _x ′(T ₂ -T ₁ ),ID _x ) （3）

Here F is key-function, and the key of designated length is produced as needed；

（First 3）NodexWillCF _x ′(T ₂ -T ₁ )+ID _x When being sent to Sink node,xOne jump in the range of neighbor node can also receive The information is simultaneously stored in oneself storage；Equally,xThe clock progress frequency and ID of other nodes can be also received as neighbor node Information, so, two nodes complete clock progress frequency and exchanged in BAN；

（First 4）In nodexOnto the path of Sink node, two adjacent nodesm、nThere are the clock progress frequency of other side, its clock The key that the ID of skew and two nodes is producedK _mn OrK _nm It is unique, for encrypting routing iinformation, two nodes are mutually recognized each other Card,K _mn OrK _nm It is identical, it is defined as follows：

K _mn =K _nm =F(CS _mn (T ₂ -T ₁ ),ID _m ,ID _n ) （4）

CS _mn (T ₂ -T ₁ ) =ABS(CF _m ′(T ₂ -T ₁ )- CF _n ′(T ₂ -T ₁ ))

Here F is key-function, with formula（3）Identical, ABS is to take absolute value；

（First 5）Sink node is received after the clock progress frequency and id information of all nodes, Sink node and each nodexShape Into a pairwise keyK _x , for encryption data in itself, two adjacent nodesm、nForm pairwise keyK _mn OrK _nm , for adding Close routing iinformation；After Sink node broadcasts " OK " information in single-hop mode, BAN enters Security routing formation and data encryption is passed The defeated stage；

After all nodes receive " OK " information, each original AODV routing iinformations of knot removal, using improved AODV agreements Form Security routing and encrypted transmission data；Improved AODV protocol messages are to increase a clock on original message basis to enter Spread spectrum rate field CF；Work as nodexWhen wishing to Sink node transmission data, first have to transmission RREQ and ask to form Sink node Security routing, then further according to the route transmit data, data source nodesxThe Security routing that request is formed to Sink node is grasped Make as follows：

（Second 1）NodexA RREQ message is produced, each field information in the inside, increased CF fields are equally filled with original AODV Use nodex'sCF _x ′(T ₂ -T ₁ ) filling, it is then broadcast to neighbor node；

（Second 2）Work as nodexNeighbor nodemWhen receiving RREQ message, point three kinds of situation operations are as follows：

If A. the CF fields in RREQ message are sky, illustrate that RREQ, from a distrust node, stops forwarding the message；

If the CF fields B. in RREQ message are present and nodemIn preserve nodexCF valuesCF _x ′(T ₂ -T ₁ ), nodemThan It is whether equal compared with both values, if equal, nodemWith the CF values of oneselfCF _m ′(T ₂ -T ₁ ) replace RREQ message interior jointsx's CF values, continue to forward the RREQ；Otherwise, stop forwarding；

If the CF fields C. in RREQ message are present and nodemIn without preserve nodexCF values, nodemJust saved to Sink Point requesting nodexCF values, if Sink node has nodexCF values, just willCF _x ′(T ₂ -T ₁ ) useK _m With single-hop side after encryption Formula is sent to nodem, nodemThe message is received to be used in combinationK _m After correct decryption, preserveCF _x ′(T ₂ -T ₁ ) in internal memory, subsequent operation It is identical with B；

（Second 3）Work as nodemNeighbor node receive after RREQ message, same to step（Second 2）Similar mode forwards RREQ message；

（Second 4）When Sink node receives RREQ message, a RREP message is produced, fills RREP's with the CF values of Sink node CF fields, then unicast is returned to the neighbor node of Sink node；

（Second 5）After the neighbor node of Sink node receives RREP message, same to step（Second 2）It is similar to pass RREP message back；

（Second 6）Work as data source nodesxWhen receiving RREP message, the Security routing that only legitimate node is participated in is formed.

2. a kind of wireless body area network safe transmission method according to claim 1, it is characterised in that N1, N2 and N3 are For node, it is assumed that N1 to Sink Security routing is N1->N2->N3->Sink, source node N1 produce by mark Tag, Data1 and The packet of Data2 compositions；Tag is type of message, and Data1 includes source ID, Target id and data generation time information, Data2 For the data of N1 actual perceiveds；In encrypted data transmission, node N1, N2, N3 and Sink operation are as follows：

（The third 1）N1：The pairwise key that Data2 is known with only N1 and Sink nodeK ₁Encryption is obtainedE(Data2,K ₁), Data1 With the pairwise key that only node N1 and N2 knowK ₁₂It is encrypted asE(Data1,K ₁₂), then send packet unicast to N2；

（The third 2）N2：First useK ₁₂Data1 is decrypted, i.e.,D(E(Data1,K ₁₂), K ₁₂) Data1 is obtained, obtain after routing iinformation again With the pairwise key that only node N2 and N3 knowK ₂₃It is encrypted asE(Data1,K ₂₃), then transfer a packet to N3；E is to add Close operation, D is decryption oprerations；

（The third 3）N3：First useK ₂₃Data1 is decrypted, i.e.,D(E(Data1,K ₂₃), K ₂₃) Data1 is obtained, obtain after routing iinformation again With the pairwise key that only node N3 and Sink node are knownK ₃₀It is encrypted asE(Data1,K ₃₀), then transfer a packet to Sink node；

（The third 4）Sink：First useK ₃₀Data1 is decrypted, i.e.,D(E(Data1,K ₃₀), K ₃₀) Data1 is obtained, obtain source node identification Afterwards, useK ₁Data2 is decrypted, i.e.,D(E(Data2,K ₁), K ₁) obtain True Data Data2.