CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Taiwan Patent Application No. 104140611, filed Dec. 3, 2015 at the Taiwan Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
       [0002]    The present disclosure relates to an authentication system and method for an electronic governor of an unmanned aerial vehicle (UAV). More particularly, the present disclosure relates to an authentication system and method that is capable of determining, according to an authentication scheme, whether the electronic governor has been modified or not, by using a main control terminal that is coupled to the electronic governor. 
       2. Description of the Related Art 
       [0003]    In past decades, small sized unmanned aircraft or model airplanes were generally only used for recreation purposes, and in competitions and shows, in the sport or pastime of aeromodelling. However, in recent years, with the rapid development of electronic technology, unmanned aerial vehicles (UAVs) have found many other uses and people have gradually started to pay more attention to the potential of UAVs. 
         [0004]    Besides their use in aeromodelling, UAVs have been applied in many other fields. For example, a UAV equipped with a camera may be used to broadcast live a sports game or a concert, or may carry out aerial photography work, as well as many other applications. A UAV equipped with a GPS module may be used in mountain rescue, disaster monitoring, delivery of goods, airborne camerawork such as tracking and filming athletes in a sporting event, or in many other applications. 
         [0005]    While the UAV market has recently been growing gradually, the use of UAVs has given rise to several problems regarding public safety. A UAV&#39;s loading capacity is determined in large part by the driving power of the motor; and this is critical, as a UAV with a greater loading capacity is able to carry more payload of a dangerous nature, and so would be more effective when used as an offensive weapon to cause damage or harm. The most popular UAV has a control system with a main control terminal that transmits control signals to an electronic governor, which then amplifies current to drive the brushless motor. In such a system, modification of the electronic governor and the motor could improve the loading capacity and flight range or maximum distance of the UAV. 
         [0006]    However, currently there are no restrictions in place to prevent the modification of the electronic governor of UAVs. A person with malicious intent may modify or replace the electronic governor of a UAV to enable the UAV to carry a heavier load or fly farther. The modified UAV may then be capable of being used for some malicious and likely illegal purpose, as well as causing unintentional damage or casualties in an accident due to the increase drive power and payload. For this reason, many national aviation authorities, such as the United States (US) Federal Aviation Administration (FAA), have started to limit the freedom of UAV use without registration or license. This also has the effect of slowing the spread in the use of UAVs and thus their further development. A possible solution is to use an authentication and data encryption regime where a master control chip authenticates the electronic governor of the UAV. This will help prevent the illegal modification of the electronic governor, and so help prevent a malicious use of a UAV that requires greater load capacity or farther range. 
       SUMMARY OF THE INVENTION 
       [0007]    An exemplary embodiment of the present disclosure provides an authentication system for an electronic governor of an unmanned aerial vehicle (UAV). The authentication system includes a main control terminal and at least one electronic governor. The main control terminal includes a first database, a first encryption and decryption module, and a first transceiver. The first database is configured to store authentication data, authenticated data and control data. The first encryption and decryption module is electrically coupled to the first database. The first transceiver is electrically coupled to the first encryption and decryption module. The at least one electronic governor includes a second transceiver, a second encryption and decryption module, a second database and a driver module. The first and second transceivers are able to transmit data between them. The second encryption and decryption module is electrically coupled to the second transceiver. The second database is electrically coupled to the second encryption and decryption module, and is configured to store the authentication data which is decrypted. The driver module is electrically coupled to the second encryption and decryption module and to a motor and is configured to control the motor. For operation, the main control terminal and the at least one electronic governor are coupled to each other and the main control terminal is started. Then, in an authentication stage, the first encryption and decryption module encrypts the authentication data stored in the first database, and then transmits the encrypted authentication data to the second transceiver via the first transceiver. Then, the second encryption and decryption module decrypts the received authentication data and stores the authentication data in the second database. After that, the second encryption and decryption module encrypts the authentication data and transmits the encrypted authentication data to the first transceiver via the second transceiver. Then, the first encryption and decryption module decrypts the received authentication data and checks whether the decrypted authentication data is the same as the authenticated data stored in the first database. If the decrypted authentication data is the same as the authenticated data stored in the first database, the main control terminal enters a control stage. In the control stage, the first encryption and decryption module encrypts the control data and transmits the encrypted control data to the second transceiver via the first transceiver. Then, still in the control stage, the second encryption and decryption module receives and decrypts the encrypted control data to generate a control signal, and the driver module controls a rotational speed of the motor according to the control signal. 
         [0008]    Preferably, in the control stage, the first encryption and decryption module of the main control terminal encrypts the authentication data and the control data, and transmits the encrypted authentication data and the encrypted control data to the second transceiver via the first transceiver. Then, after decrypting the encrypted authentication data and the encrypted control data, the second encryption and decryption module determines whether the decrypted authentication data is the same as the authentication data stored in the second database. If the decrypted authentication data is the same as the authentication data stored in the second database, then the driver module controls the rotational speed of the motor according to the decrypted control signal. If, on the other hand, the decrypted authentication data is not the same as the authentication data stored in the second database, then the driver module disregards the decrypted control signal. 
         [0009]    Preferably, if the second encryption and decryption module determines the received control data to be unencrypted, then the driver module controls the rotational speed of the motor according to the received control data. 
         [0010]    Preferably, the first encryption and decryption module encrypts the authentication data first, and then the second encryption and decryption module decrypts the encrypted authentication data. After that, the second encryption and decryption module encrypts the authentication data again. Then, the first encryption and decryption module decrypts the authentication data encrypted by the second encryption and decryption module, thus generating the authenticated data which is stored in the first database. 
         [0011]    Preferably, the main control terminal further includes a random number generator configured to generate the authentication data. The authenticated data is then generated according to the authentication data which is generated by the random number generator. 
         [0012]    What follows is an exemplary embodiment of the present disclosure. The exemplary embodiment provides an authentication method for an electronic governor of an unmanned aerial vehicle (UAV). The authentication method is applied to the authentication system described above, and the authentication method includes the following steps. First, electrically coupling the main control terminal to the at least one electronic governor, and starting the main control terminal. Then, in an authentication stage, encrypting the authentication data stored in the first database by the first encryption and decryption module; transmitting the encrypted authentication data to the second transceiver via the first transceiver; receiving and decrypting the encrypted authentication data by the second encryption and decryption module; and storing the authentication data in the second database. After that and still in the authentication stage, encrypting the authentication data again by the second encryption and decryption module; transmitting the encrypted authentication data to the first transceiver via the second transceiver; decrypting the received authentication data by the first encryption and decryption module; and determining whether the received authentication data is the same as the authenticated data stored in the first database. If the received authentication data is the same as the authenticated data stored in the first database, then the main control terminal enters a control stage, which includes the following steps. Encrypting the control data by the first encryption and decryption module and transmitting the encrypted control data to the second transceiver via the first transceiver. Then, still in the control stage, decrypting the received control data by the second encryption and decryption module; and finally controlling the rotational speed of the motor by the driver module according to the decrypted control signal. 
         [0013]    Preferably, in the control stage, the authentication method further includes the steps of: first, encrypting the authentication data and the control data by the encryption and decryption module; then, transmitting the authentication data to the second transceiver via the first transceiver; receiving and decrypting the encrypted authentication data and the control data by the second encryption and decryption module; determining whether the decrypted authentication data is the same as the authentication data previously stored in the second database by the second encryption and decryption module; and finally controlling the rotational speed of the motor by the driver module according to the decrypted control signal if the decrypted authentication data is the same as the authentication data previously stored in the second database; or on the other hand, disregarding the decrypted control signal if the decrypted authentication data is not the same as the authentication data previously stored in the second database. 
         [0014]    Preferably, the driver module is configured to control the rotational speed of the motor according to the received control data in the case that the second encryption and decryption module determines that the received control data is unencrypted. 
         [0015]    Preferably, prior to the authentication stage, the authenticated data stored in the first database is encrypted by the first encryption and decryption module. After that, the encrypted authenticated data is decrypted first and then encrypted again by the second encryption and decryption module. The authenticated data encrypted by the second encryption and decryption module is then decrypted again by the first encryption and decryption module, thus generating the authenticated data which is stored in the first database. 
         [0016]    Preferably, the main control terminal further includes a random number generator configured to generate the authentication data. The authenticated data is generated according to the authentication data which is generated by the random number generator. 
         [0017]    Advantages of the authentication system and method for an electronic governor of a UAV of the present disclosure include, but are not limited to, the following. 
         [0018]    (1) The authentication system and method is able to prevent replacement of an authenticated electronic governor with an unauthenticated electronic governor that is able to function, for instance for use by a person with malicious intent. The control data transmitted to the electronic governor is also encrypted, which implies that the unauthenticated electronic governor is unable to function if it fails to decrypt the encrypted control signal. This adds a further safeguard for the authentication system and method to prevent the replacement of the authenticated electronic governor with the unauthenticated electronic governor with the aim of modify the UAV to carry a heavier load or fly farther for some illegal purpose. 
         [0019]    (2) The authentication system and method may be operated in dual mode. That is to say, that the electronic governor is able to function with the driver module controlling the rotational speed of the motor according to the received control data, regardless of whether the control data is encrypted or unencrypted. This extends the compatibility of the electronic governor so that the electronic governor is able to function with conventional main control terminals. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The structure, operating principle and effects of the present disclosure will be described in detail by way of various embodiments which are illustrated in the accompanying drawings. 
           [0021]      FIG. 1  is a block diagram of an embodiment of an authentication system for an electronic governor of an unmanned aerial vehicle (UAV) in accordance with the present disclosure. 
           [0022]      FIG. 2  is a block diagram of another embodiment of the authentication system for an electronic governor of a UAV in accordance with the present disclosure. 
           [0023]      FIG. 3  is a schematic view of the authentication system of the present disclosure, showing the authentication system installed in the UAV. 
           [0024]      FIG. 4  is a flowchart of an embodiment of an authentication method for an electronic governor of a UAV in accordance with the present disclosure. 
           [0025]      FIGS. 5A and 5B  are flowcharts of another embodiment of the authentication method for an electronic governor of a UAV in accordance with the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    The following embodiments of the present invention are herein described in detail with reference to the accompanying drawings. These drawings show specific examples of the embodiments of the present invention. It is to be understood that these embodiments are exemplary implementations and are not to be construed as limiting the scope of the present invention in any way. Further modifications to the disclosed embodiments, as well as other embodiments, are also included within the scope of the appended claims. These embodiments are provided so that this disclosure is thorough and complete, and fully conveys the inventive concept to those skilled in the art. Regarding the drawings, the relative proportions and ratios of elements in the drawings may be exaggerated or diminished in size for the sake of clarity and convenience. Such arbitrary proportions are only illustrative and not limiting in any way. The same reference numbers are used in the drawings and description to refer to the same or like parts. 
         [0027]    It is to be understood that, although the terms ‘first’, ‘second’, ‘third’, and so on, may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only for the purpose of distinguishing one component from another component. Thus, a first element discussed herein could be termed a second element without altering the description of the present invention. As used herein, the term “or” includes any and all combinations of one or more of the associated listed items. 
         [0028]    The following refers to  FIG. 1 , which is a block diagram of an embodiment of an authentication system for an electronic governor of an unmanned aerial vehicle (UAV) of the present disclosure. The authentication system  1  includes a main control terminal  100  and at least one electronic governor  102 . The main control terminal  100  includes a first database  108 , a first encryption and decryption module  106  and a first transceiver  104 . The first database  108  is configured to store authentication data  110 , authenticated data  112  and control data  114 . The main control terminal  100  is wirelessly coupled to the flight controller through the first transceiver  104 . The main control terminal  100  is also coupled to a power supply unit, such as a storage battery. The technology of the power supply unit is well known for a person with ordinary skill in the art, therefore the power supply unit is not described here any further. The main control terminal  100  includes a central processing unit, a microprocessor, a network processor, a microcontroller or an integrated circuit (IC) dedicated to carry out the functions of the aforementioned modules. 
         [0029]    The first encryption and decryption module  106  is electrically coupled to the database  108 . The first transceiver  104  is electrically coupled to the first encryption and decryption module  106 . The electronic governor  102  includes a second transceiver  116 , a second encryption and decryption module  118 , a second database  120  and a driver module  124 . The second transceiver  116  is electrically coupled to the first transceiver  104  in a wired or wireless manner for the purpose of data transmission. The second encryption and decryption module  118  is electrically coupled to the second transceiver  116 . The second database  120  is configured to store authentication data  122  which is decrypted. The driver module  124  is electrically coupled to the motor  126  and configured to control the motor  126 . 
         [0030]    Preferably, the first transceiver  104  and second transceiver  116  may be a WiMax module, a Wi-Fi module, a Bluetooth module, a 2G/3G/4G or LTE module, or the like, so as to enable communication between the two transceivers using the same chosen protocol. For example, the Wi-Fi module is able to communicate with other Wi-Fi communication devices (such as a wireless access point which is also known as a base station, other Wi-Fi nodes in a wireless ad hoc network, or the like) that are compliant with the Wi-Fi or 802.11 protocol, whereas the Bluetooth module is able to communicate with other Bluetooth communication devices (such as a mobile telephone, a Bluetooth headphone or the like) that are compliant with the Bluetooth or 802.15 protocol. The first database  108  or second database  120  may be a semiconductor memory device (such as a flash memory device), an auxiliary memory device (such as a hard disk drive or solid state drive), or storage media (such as a Digital Versatile Disk or an SD memory card). 
         [0031]    In order to prevent the use of an illegally modified electronic governor, the authentication and data encryption scheme must be installed between the main control terminal  100  and the electronic governor  102  of a UAV. On coupling of the main control terminal  100  to the electronic governor  102  and powering of the main control terminal  100 , the authentication system  1  enters an authentication stage. In the authentication stage, the first encryption and decryption module  106  encrypts the authentication data  110  stored in the first database  108 , and the encrypted authentication data  110  is transmitted to the second transceiver  116  via the first transceiver  104 . Preferably, the authentication data  110  is a unique ID of the UAV which has been previously set in the factory that manufactures the UAV. The second encryption and decryption module  118  decrypts the received authentication data  110 , and stores the decrypted authentication data  110  as the authentication data  122  in the second database  120 . The first encryption and decryption module  106  and the second encryption and decryption module  118  apply an encryption and decryption algorithm that may be a disk encryption algorithm which supports the CBC, LRW, XEX, XTS, CMC, EME or ESSIV encryption algorithms. The first and second encryption and decryption modules  106  and  118  may apply the above-mentioned encryption algorithms with a key of 128 bits or 256 bits to perform encryption and decryption of the data. 
         [0032]    Still in the authentication stage, the second encryption and decryption module  118  then encrypts the authentication data  122  again, and transmits the encrypted authentication data  122  to the first transceiver  104  via the second transceiver  116 . The first encryption and decryption module  106  then decrypts the received authentication data  122 , and checks whether the decrypted authentication data  122  is the same as the authenticated data  112  stored in the first database  108 . If the decrypted authentication data  122  is the same as the authenticated data  112 , the main control terminal  100  is permitted to receive the control command from a flight controller to control the UAV. The main control terminal  100  then generates the control data  114 , and the control data  114  is stored in the first database  108 . In order to control the motor  126 , the first encryption and decryption module  106  encrypts the control data  114  and transmits the encrypted control data  114  to the second transceiver  116  via the first transceiver  104 . Next, the second encryption and decryption module  118  decrypts the received control data  114  to generate a control signal, and then the driver module  124  controls the rotational speed of the motor  126  according to the control signal. If, on the other hand, the first encryption and decryption module  106  determines that the authentication data  122  is different from the authenticated data  112  of the first database  108 , then the electronic governor  102  is not an authenticated electronic governor and the main control terminal  100  is not permitted to control the motor  126  of the electronic governor  102 , thereby preventing the use of an illegally modified electronic governor of the UAV. 
         [0033]    In another embodiment of the authentication system  1 , a control stage follows the storage of the decrypted authentication data  110  as the authentication data  122  in the second database  120 . The authentication data  110  and control data  114  are encrypted by the first encryption and decryption module  106  of the main control terminal  100 . Then the encrypted authentication data  110  and control data  114  are transmitted to the second transceiver  116  via the first transceiver  104 . The second encryption and decryption module  118  then decrypts the authentication data  110  and control data  114 , and from the decrypted control data  114  results a control signal. The second encryption and decryption module  118  then determines whether the decrypted authentication data  110  is the same or not the same as the authentication data  122  previously stored in the second database  120 . If the decrypted authentication data  110  is the same as the authentication data  122  previously stored in the second database  120 , then the driver module  124  controls the rotational speed of the motor  126  according to the decrypted control signal. If, on the other hand, the decrypted authentication data  110  is not the same as the authentication data  122  previously stored in the second database  120 , then the control signal is ignored. As a result, the authentication system  1  is able to prevent a person with malicious intent from using an unauthenticated electronic governor. The encryption of the control data  114  prior to being sent to the electronic governor is a further safeguard that adds to the difficulty for a person with malicious intent to use the unauthenticated electronic governor that has been modified to allow the UAV to carry a heavier load or to fly farther. 
         [0034]    Regarding the authentication stage, the following may be carried out in advance. The authentication data is encrypted by the first encryption and decryption module  106 . Then, the second encryption and decryption module  118  decrypts the encrypted authentication data first and then encrypts the authentication data again. The first encryption and decryption module  106  then decrypts the authentication data encrypted by the second encryption and decryption module  118 , to generate the authenticated data  112  which is stored in the first database  108 . When the main control terminal  100  and the electronic governor  102  are coupled to each other, the resulting authentication data decrypted by the first encryption and decryption module  106  must be the same as the authenticated data  112  stored in the first database  108  for authentication of the electronic governor  102 . 
         [0035]    The following refers to  FIG. 2 , which is a block diagram of another embodiment of the authentication system for an electronic governor of a UAV of the present disclosure. The authentication system  2  for the electronic governor of the UAV includes a main control terminal  200  and at least one electronic governor  202 . The main control terminal  200  includes a first database  208 , a first encryption and decryption module  206  and a first transceiver  204 . The first database  208  is configured to store authentication data  210 , authenticated data  212  and control data  214 . The electronic governor  202  includes a second transceiver  216 , a second encryption and decryption module  218 , a second database  220  and a driver module  224 . The configuration of these elements is the same as that of the authentication system  1  of the embodiment illustrated in  FIG. 1 , so their detailed description is not repeated here. The difference between the present embodiment and the former embodiment illustrated in  FIG. 1 , is that in the present embodiment the main control terminal  200  further includes a random number generator  228  configured to generate the authentication data  210 . This results in the authenticated data  212  being generated from the authentication data  210 , which is itself generated by the random number generator  228 . In the authentication stage, when the first encryption and decryption module  206  encrypts the authentication data  210 , the authentication data  210  is combined with the ID of the master device, the master device being the main control terminal  200 , and the combined data is then encrypted using a public key of the electronic governor  202 . After that, the second encryption and decryption module  218  decrypts the received authentication data by using a private key of the ESC, to obtain the authentication data  222 . 
         [0036]    The control data  114  and  214  may be pulse-width modulation (PWM) signals. The first encryption and decryption module  206  may encrypt the PWM signals by using the public key of the ESC, in order to prevent use of an unauthenticated electronic governor. That is to say, the functioning of the electronic governor depends on the electronic governor being able to decrypt the received encrypted control data  214 . 
         [0037]    The electronic governors  102  and  202  of the present disclosure are able to operate in dual mode so that the electronic governors  102  and  202  are compatible with the main control terminals that are commercially available. Dual mode includes the mode where the driver modules  114  and  224  directly control the rotational speeds of the motors  126  and  226  according to the received control data, even though the second encryption and decryption modules  118  and  218  of the electronic governors  102  and  202  have determined that the received control data is not encrypted. The received control data is not encrypted when the main control terminal coupled to the electronic governor  102  or  202  is a conventional main control terminal. Therefore, by operating the authentication system in dual-mode, the electronic governor is able to receive the control data in encrypted or unencrypted form. This extends the compatibility of the electronic governor with the authentication function, so that the electronic governor is also able to function with conventional main control terminals. 
         [0038]    The following refers to  FIG. 3 , which is a schematic view of the authentication system and the UAV the authentication system is applied to, in accordance with the present disclosure. Four motors  306  of an unmanned aerial vehicle  3  are coupled to each of multiple electronic governors  302  through electronic wire  304 , and each of the electronic governors  302  is coupled to the main control terminal  300  through data wire. The configuration of the main control terminal  300  and of the electronic governors  302  is the same as that in the previous embodiments, so their detailed description is not repeated here. The authentication scheme provided by the authentication system for an electronic governor of a UAV does not allow the user to use a new electronic governor after replacement of any of the electronic governors  302  until the new electronic governor is authenticated. Also, the electronic governor of the present disclosure is able to function in dual-mode, such that if the electronic governor of the present disclosure detects that the received control signal is an unencrypted signal, the driver module is still able to directly drive the motor  306  according to the control signal. This dual-mode function allows for the use of conventional main control terminals, which produce an unencrypted control signal. Therefore, such conventional main control terminals can still be used with the electronic governor  302  of the present disclosure, even though conventional main control terminals are not fully compliant with the authentication scheme of the present disclosure. 
         [0039]    An authentication method adapted to the authentication system for an electronic governor of an unmanned aerial vehicle of the present disclosure is described below, with reference to the accompanying drawings. The following steps are reproduced from the flow charts of  FIGS. 4, 5A and 5B , and are each followed with further description. 
         [0040]    The following refers to  FIG. 4 , which is a flowchart of an embodiment of the authentication method for an electronic governor of a UAV, in accordance with the present disclosure. The authentication method includes following steps. 
         [0041]    S 401 : Coupling the main control terminal to the at least one electronic governor and starting the main control terminal. When the UAV is supplied with power, the main control terminal starts to authenticate the electronic governor. 
         [0042]    S 402 : In an authentication stage of the authentication system, encrypting the authentication data stored in the first database by the first encryption and decryption module, and transmitting the encrypted authentication data to the second transceiver via the first transceiver. The authentication data  112  may be a unique ID of the UAV which has been previously set in the factory that manufactures the UAV. 
         [0043]    S 403 : Decrypting the received authentication data by the second encryption and decryption module, storing the authentication data in the second database, and encrypting the authentication data again by the second encryption and decryption module. The encryption and decryption algorithm applied by the first and second encryption and decryption modules may be one of the encryption algorithms already described in the previous embodiments, and so their detailed description is not repeated here. 
         [0044]    S 404 : Transmitting the encrypted authentication data to the second transceiver via the first transceiver, and decrypting the received encrypted authentication data by the first encryption and decryption module. 
         [0045]    S 405 : Comparing the received authentication data with the authenticated data stored in the first database. If the received authentication data is the same as the authenticated data, the authentication method proceeds to a step S 406  where in a control stage of the authentication system, the first encryption and decryption module encrypts the control data, and after that a step S 407  follows, which is described below. If, on the other hand, the received authentication data is not the same as the authenticated data, the authentication system returns to the step S 402  after a time period. The authentication system then carries out the step S 402  again, where the first encryption and decryption module again encrypts the authentication data stored in the first database, and the encrypted authentication data is again transmitted to the second transceiver via the first transceiver. 
         [0046]    S 407 : Transmitting the encrypted control data to the second transceiver via the first transceiver, decrypting the received control data by the second encryption and decryption module, and controlling the rotational speed of the motor according to the decrypted control signal. 
         [0047]    The following refers to  FIGS. 5A and 5B , which are flowcharts of another embodiment of the authentication method for an electronic governor of a UAV, in accordance with the present disclosure. This embodiment of the authentication method for an electronic governor of an unmanned aerial vehicle may also be applied to the authentication system of the present disclosure. The embodiment includes a pre-authentication stage, an authentication stage and a control stage. The pre-authentication stage includes following steps, which are also shown in  FIG. 5A . 
         [0048]    S 501 : Generating authentication data of a random nature by the random number generator. 
         [0049]    S 502 : Combining the authentication data and the ID of the master device and encrypting the combined data by using the public key of the ESC by the first encryption and decryption module. 
         [0050]    S 503 : Transmitting the encrypted data to the second transceiver via the first transceiver. 
         [0051]    S 504 : Decrypting the received encrypted data by using the private key of the ESC by the first encryption and decryption module, to obtain further authentication data. 
         [0052]    S 505 : Encrypting, by the first encryption and decryption module, the further authentication data which was generated in step S 504  by using the private key of the ESC, and transmitting the encrypted further authentication data to the second transceiver via the first transceiver. 
         [0053]    S 506 : Decrypting the received encrypted further authentication data by using the public key of the ESC by the second encryption and decryption module to obtain the authenticated data, and storing the authenticated data in the first database. 
         [0054]    The authentication stage and the control stage include the following steps, which are also shown in  FIG. 5B . 
         [0055]    S 507 : In the authentication stage of the authentication system, carrying out the above-described steps S 401 -S 405 , whose detailed descriptions are not repeated here. 
         [0056]    S 508 : In the control stage of the authentication system, encrypting the authentication data and the control data by the first encryption and decryption module, and transmitting the encrypted authentication data and the encrypted control data to the second transceiver via the first transceiver. 
         [0057]    S 509 : Determining whether the received data is encrypted by the second encryption and decryption module. Then, if the received data is encrypted, decrypting the received data in a step S 510  by the second encryption and decryption module. Then, after that, proceeding with a step S 511 . However, on the other hand, if the received data is not encrypted, then interpreting the received control data as a control signal, and then in a step S 512 , controlling the rotational speed of the motor by the driver module according to the control signal. 
         [0058]    S 511 : Determining whether the decrypted authentication data is the same as the authentication data stored in the second database. Then, if the decrypted authentication data is the same as the authentication data stored in the second database, controlling the rotational speed of the motor by the driver module according to the control signal, which is the step S 512 . However, on the other hand, if the decrypted authentication data is not the same as the authentication data stored in the second database, then disregarding the control signal by the driver module. 
         [0059]    In summary, the authentication system and the method thereof of the present disclosure is able to prevent replacement of an authenticated electronic governor with an unauthenticated electronic governor that is able to function. The control data transmitted to the electronic governor is also encrypted, which implies that the unauthenticated electronic governor is unable to function if it fails to decrypt the encrypted control signal. This adds a further safeguard in preventing people with malicious intent from using an unauthenticated electronic governor that has been modified so that the unmanned aerial vehicle is able to carry heavier loads or fly farther. Another feature is that the authentication system and method for an electronic governor of a UAV may be selectively operated in two modes, one mode for operating with encrypted control data and the other mode for operating with unencrypted control data, thereby extending the compatibility of the electronic governor so that the electronic governor is also able to function with conventional main control terminals that do not encrypt the control data. 
         [0060]    The invention disclosed herein has been described by means of specific embodiments. However, numerous modifications, variations and enhancements can be made thereto by those skilled in the art without departing from the spirit and scope of the invention set forth in the claims.
An authentication system and method for an electronic governor of an unmanned aerial vehicle is disclosed. By employing reciprocative authentication and encryption mechanisms between a main control terminal and an electronic governor, the use of a modified electronic governor is prevented and thus the illegal use of UAVs is also prevented. Moreover, the provided electronic governor may be operated in dual-mode to extend its compatibility to conventional main control terminals.