JPH09114372A - Transmitter, receiver and methods thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit a password of a credit card without being known by others. SOLUTION: A first encoding means 53 encodes the password by a first encoding key causing random numbers to generate the first encoding data added with the first encoding key. A second encoding means 55 performs the second encoding processing referring to a reference table 56 based on a second encoding key causing the random numbers. Then, the means 55 generates the second encoding data added with the second encoding key. A third encoding means 57 encodes the second encoding data by a third encoding key causing the random numbers to generate the third encoding data added with the third encoding key. A transmission means 59 transmits the third encoding data. In such a manner, by performing multiplexed encoding, sure encoding is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for transmitting and receiving a secret code having a predetermined number of digits, and more particularly to encryption of a secret code.

[0002]

[Related Art and Problems to be Solved by the Invention] FIG.
Shows an online shopping system that the inventor considered. The online shopping system will be briefly described. The center (sales company) is connected to each user online, and the center is connected to the credit company online. The center distributes the catalog to each user. This catalog is supplied to the user as electronic data or printed matter.
The user places an order for the desired product in the catalog online at the center. At that time, own credit data is transmitted at the same time. The center requests the credit company to verify the sent credit data. The credit company sends the verification result to the center.
When the collation result is credit OK, the ordering is completed for the user. Since it is possible to order the products online in this way, it is possible to order the desired products in real time without any trouble.

However, in the online shopping system, the user's name, credit card number and personal identification number are transmitted online as the credit data. In this case, if this credit data remains on the computer at the center, it may be misused by a third party.

[0004] It is an object of the present invention to provide a transmitting / receiving method capable of transmitting a personal identification number of a credit card without being known to others and enabling online shopping.

[0005]

According to a first aspect of the present invention, there is provided a transmitting device for transmitting a personal identification number having a predetermined number of digits.
By encrypting the personal identification number with the first encryption key,
First encryption means for generating first encrypted data to which an encryption key is added, second encryption key to which the first encrypted data is encrypted, and second encryption key to which the second encrypted key is added Second encryption means for generating encrypted data, third encryption for encrypting the second encrypted data with a third encryption key, and generating third encrypted data to which the third encryption key is added And a transmitting means for transmitting the third encrypted data.

According to a second aspect of the present invention, the first encryption key to the third encryption key are determined by generating a random number.

In the transmitting apparatus of claim 3, the second
Of the encryption means has a reference table composed of the second encryption key and rearrangement order determination data corresponding to the second encryption key, and when the second encryption key is specified, the reference table is opened. With reference to the above, the second encryption processing is performed.

In the transmitting device of claim 4, the personal identification number is a four-digit personal identification number of a credit card, and the first encryption key is composed of four digits, and the first encryption means. Performs the first encryption processing by adding each digit of the first encryption key to the personal identification number, and the second encryption key is composed of four digits. The encryption means rearranges the digits of the personal identification number to which the first encryption key is added, based on the second encryption key, referring to the reference table, and the third encryption key is composed of two digits. Based on the third encryption key, the third encryption means determines a digit which is the head position of the personal identification number to which the first and second encryption keys are added, and sequentially arranges the digits. It is characterized by changing.

According to another aspect of the invention, there is provided a receiving device which receives a personal identification number encrypted with the first to third encryption keys and to which the first to third encryption keys are added, and which performs a decryption process. Which of the receiving means for receiving the personal identification number to which the first encryption key to the third encryption key are added and the personal identification number to which the first encryption key to the third encryption key are added are Third decryption means for generating a personal identification number to which the first and second encryption keys are added by identifying whether the key is a third encryption key and decrypting with the third encryption key. By identifying which of the personal identification numbers to which the first and second encryption keys are added is the second encryption key, and decrypting with this second encryption key, the first encryption key is Second decryption means for generating the added personal identification number, the first encryption Is one of over is appended PIN to identify whether a first encryption key, by decoding in the first encryption key, said first encryption key ~
It is characterized by further comprising first decryption means for generating a personal identification number before being encrypted by the third encryption key.

In the transmission method of claim 6, the personal identification number is encrypted with a first encryption key to generate first encrypted data to which the first encryption key is added, and the first encryption key is generated. The data is encrypted with the second encryption key to generate the second encrypted data to which the second encryption key is added, and the second encrypted data is encrypted with the third encryption key. It is characterized in that third encrypted data to which three encryption keys are added is generated and the third encrypted data is transmitted.

In the receiving method of claim 7, the first
The personal identification number to which the encryption key to the third encryption key are added is received, and which of the personal identification numbers to which the first encryption key to the third encryption key is added is the third encryption key. By identifying and decrypting with the third encryption key, a personal identification number to which the first and second encryption keys are added is generated, and a personal identification number to which the first and second encryption keys are added. Identify which of these is the second encryption key,
By decrypting with the second encryption key, the first
A personal identification number to which an encryption key is added is generated, which of the personal identification numbers to which the first encryption key is added is the first encryption key, and decryption is performed using this first encryption key. By doing so, the personal identification number before being encrypted by the first encryption key to the third encryption key is generated.

[0012]

According to the transmission device of claim 1 and the transmission method of claim 6, the third encryption to which the first encryption key, the second encryption key, and the third encryption key are added. Send data. Therefore, the personal identification number can be transmitted without being known.

In the transmitting apparatus of the second aspect, the first encryption key to the third encryption key are determined by generating a random number. Therefore, since the encryption key is changed each time, it becomes difficult for a person who does not know the encryption algorithm to perform the decryption.

In the transmitting apparatus of claim 3, the second
Of the encryption means has a reference table composed of the second encryption key and rearrangement order determination data corresponding to the second encryption key, and when the second encryption key is specified, the reference table is opened. With reference to the above, the second encryption processing is performed. Therefore, even if the algorithm is known, anyone who does not have this lookup table cannot decrypt it.

In the transmitting device of claim 4, the personal identification number is a four-digit personal identification number of a credit card, and the first encryption key is composed of four digits, and the first encryption means. Performs the first encryption processing by adding each digit of the first encryption key to the personal identification number. The second encryption means rearranges the digits of the personal identification number to which the first encryption key is added, with reference to the reference table, based on the second encryption key. The third encryption means is configured to use the first and second encryption keys based on the third encryption key.
The digit at the beginning of the personal identification number to which the encryption key has been added is determined and rearranged sequentially. Decoding becomes more difficult by performing different encryption in multiple stages in this way.

In the receiving device or the method thereof according to claims 5 and 7, when the personal identification number to which the first to third encryption keys are added is received, the third encryption key is specified. , And decryption to generate a personal identification number to which the first and second encryption keys are added. Next, the second encryption key is specified and decrypted to generate a personal identification number to which the first encryption key is added. Next, the first encryption key is specified and decrypted to generate a personal identification number before being encrypted by the first encryption key to the third encryption key. In this way, the personal identification number before encryption can be obtained from the encrypted personal identification number.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS

1. Description of Functional Block Diagram An embodiment of the present invention will be described with reference to the drawings. The transmitting device 50 shown in FIG. 1 is a device for transmitting a personal identification number having a predetermined number of digits, and comprises a first encryption means 53, a second encryption means 55,
The third encryption means 57 and the transmission means 59 are provided.

The first encryption means 53 determines the first encryption key by generating a random number. The first encryption means 53 encrypts the personal identification number with a first encryption key to generate first encrypted data to which the first encryption key is added.

The second encryption means 55 determines the second encryption key by generating a random number. The second encryption means 55 has a reference table 56 composed of a second encryption key and rearrangement order determination data corresponding to the second encryption key. When the second encryption key is specified, the second encryption process is performed by referring to the reference table 56.
Then, the second encrypted data to which the second encryption key is added is generated.

The third encryption means 57 determines a third encryption key by generating a random number. The third encryption means 57 encrypts the second encrypted data with a third encryption key to generate third encrypted data to which the third encryption key is added. The transmitting means 59 transmits the third encrypted data.

Further, the receiving device 70 is a receiving device which receives the personal identification number encrypted with the first to third encryption keys and to which the first to third encryption keys are added, and which performs a decryption process. . The receiving device 70 includes a receiving means 79 and a third decoding means 7.
7, second decoding means 75, and first decoding means 73.

The receiving means 79 receives the personal identification number to which the first to third encryption keys are added. The third decryption means 77 identifies which of the personal identification numbers to which the first encryption key to the third encryption key is added is the third encryption key, and decrypts with this third encryption key. By generating the password, the personal identification number to which the first and second encryption keys are added is generated. The second decryption means 75 has a reference table 76 composed of a second encryption key and rearrangement order determination data corresponding to the second encryption key. Second decoding means 7
5 identifies which of the personal identification numbers to which the first and second encryption keys are added is the second encryption key. Then, when the second encryption key is specified, by referring to this reference table 76 and decrypting it,
A personal identification number to which the first encryption key is added is generated.
The first decryption means 73 specifies which of the personal identification numbers to which the first encryption key is added is the first encryption key, and decrypts with the first encryption key, thereby A personal identification number before being encrypted with the first encryption key to the third encryption key is generated.

Such a transmitting device 50 is included in the user side terminal shown in FIG. 10, and the receiving device 70 is included in the credit company side terminal shown in FIG.

2. Hardware Configuration FIG. 2 shows an example of a hardware configuration in which the transmitter 50 shown in FIG. 1 is realized by using a CPU.

The transmitting device 50 includes a CPU 23 and a memory 2.
5, hard disk 26, CD-ROM 38, CRT2
9, an FDD 25, a keyboard 31, a mouse 32, an input / output interface 35, and a bus line 30. The CRT 29 may be composed of a liquid crystal display device.

The CPU 23 controls each unit via the bus line 30 according to the control program stored in the hard disk 26.

This control program is read out from the flexible disk storing the program via the FDD 25 and stored (installed) in the hard disk 26. A reference table (see FIG. 7) described later is stored in the hard disk 26. The memory 25 stores the calculation result and the like. On the CRT 29, data for ordering, a message indicating whether or not the acceptance is completed, and the like are displayed.

A communication circuit 37 is connected to the input / output interface 35. The communication circuit 37 sends and receives data by wire or wirelessly.

The hardware configuration of the receiving device 70 is the same as that of the transmitting device 50. The center side (Fig. 1
0) has a communication function, and its hardware configuration is the same as that of the transmission device 50.

3. Flowchart Next, the programs stored in the hard disks 26 of the user side, the center side, and the credit company side will be described with reference to FIGS. 3 and 4. On the user side, the user designates a product using the keyboard 31 or the mouse 32 (step ST1 in FIG. 3). The center side may provide the data for designating the product to each user in the form of a printed matter, or the data may be provided in a CD (compact disc), read by the CD-ROM 38, and the contents of the distributed CD are displayed on the CRT 29. You may do it.

Next, the user has his own credit number,
The name is input (step ST3), and then the personal identification number (4 digits) is input (step ST5). The CPU 23 on the user side encrypts the input personal identification number (step ST7).

This encryption will be described with reference to FIG. The CPU 23 first generates a random number for the addition key (see FIG. 5).
Step ST101). For example, as shown in FIG. 6A,
When the 4-digit personal identification number “2869” is entered, the screen shown in FIG.
It is assumed that a 4-digit addition key "3788" as shown in B is randomly generated. The CPU 23 uses the addition key "378
8 "is used to perform the first encryption processing of the password" 2869 "(step ST103 in FIG. 5).

In this embodiment, the following processing is performed as the first encryption processing. First, the PIN code is arranged after the addition key. As a result, "3788286
9 ”is obtained. Next, the number is changed to a number obtained by adding the first number "3" of the addition key and the first number "2" of the personal identification number. In this case, 3 + 2 gives 5. Add all this in the form of the second number, the third number, the fourth number. As a result, the first encrypted data "37885547" with the addition key as shown in FIG. 6D is obtained. In the present embodiment, when a two-digit value is obtained by the addition processing, for example, 7 + 8 = 15.
In such a case, the carry amount is ignored and 5 is used as the data after addition.

Next, the CPU 23 generates a random number for the permutation determination key (step ST105). Permutation decision key is 4
It is composed of digits. In addition, as shown in FIG.
A reference table composed of the arrangement order corresponding to this permutation determination key is stored in the hard disk 26 on the user side. Therefore, the CPU 23 executes step ST105.
The reference table shown in FIG. 7 is searched based on the permutation determination key obtained in step S1 to determine the arrangement order (step ST1).
07). The second encryption processing is performed based on this arrangement order (step ST109).

In this embodiment, the second encryption processing is performed as follows. First, the first encrypted data “3
A permutation determination key “5258” is added before “78885547”. Then, with this permutation determination key "5258",
The first encrypted data “37885547” shown in D is rearranged. Specifically, referring to FIG. 7, the arrangement order corresponding to the permutation determination key “5258” is “325687.
14 ”. That is, the third number “8” shown in FIG. 6D becomes the number next to the permutation determination key “5258” (that is, the fifth), and the second number “7” shown in FIG. 6D becomes the next number. Sorting is done in this way. In this way, the second encrypted data “525887 with the permutation determination key added as shown in FIG. 6F is added.
557438 "can be obtained.

Next, the CPU 23 generates a random number for the head determination key (step ST111 in FIG. 5). CPU23
Performs a third encryption process using this head determination key (step ST113 in FIG. 5). In this embodiment,
The following processing was performed as the third encryption processing. First, a two-digit number is generated as the leading determination key. For example, when "04" is generated as the generated two-digit number, the second encrypted data "525888757438" is arranged after this head determination key "04". This allows
“045258875757438” is obtained. Next, as shown in FIG. 6H, the second encrypted data “5258
The second number so that the fourth number after “875557438” becomes the number next to the leading decision key (that is, the third number).
Swaps the beginning position of encrypted data. In addition, "5258 ..." Is continuously arranged behind this "7438". This makes it possible to obtain the third encrypted data “04744385288755” to which the leading determination key is added.

The CPU 23 stores the obtained third encrypted data in the hard disk 26 (step ST1 in FIG. 5).
15). In the present embodiment, since triple encryption is performed, even if the encrypted data is stolen, there is less risk that the personal identification number will be obtained by another person. Also,
For one of the encryptions, since the reference table is used, it cannot be decrypted only by knowing the encryption algorithm.

Next, the CPU 23 on the user side makes a communication request to the CPU 23 on the center side (step ST9 in FIG. 3). The CPU 23 on the center side repeatedly determines whether or not there is a communication request (step ST31), and if there is a communication request, transmits a transmission start permission signal (step ST).
33). The CPU 23 on the user side determines whether or not the transmission start permission signal is received (step ST11), and when the transmission start permission signal is received, the product data and the credit data are transmitted (step ST13).

Product data refers to the code number of a product and the number of products. Credit data refers to a name, a credit card number, and a personal identification number. The personal identification number encrypted in step ST7 is transmitted.

When the product data and the credit data are transmitted from the CPU 23 on the user side, the CP on the center side is sent.
U23 receives the product data and credit data (step ST35).

The CPU 23 on the center side makes a communication request to the CPU 23 on the credit company side (step ST
37). The CPU 23 on the credit company side repeatedly determines whether or not there is a communication request (step ST7).
0), when there is a communication request, a transmission start permission signal is transmitted (step ST73). After making a communication request, the CPU 23 on the center side determines whether or not there is a transmission start permission signal (step ST39), and when the communication start permission signal is sent, the credit data is transmitted (step S).
T41). The CPU 23 on the credit company side receives the sent credit data (step ST75).

The CPU 23 of the credit company carries out the decryption processing of the personal identification number of the sent credit data (step ST77 in FIG. 4). About this decryption process,
This will be described with reference to FIG.

The CPU 23 specifies the leading determination key among the encrypted personal identification numbers sent (step ST121 in FIG. 8). In the present embodiment, since the leading decision key has the leading two digits, for example, when the received personal identification number is "0474385258875" shown in FIG. 6H, the leading two digits "04" is the leading decision key. recognize.

Next, the CPU 23 on the credit company side
Performs the decryption process for the third encrypted data (step ST123 in FIG. 8). In the present embodiment, the leading determination key “04” in the third encrypted data is 1
This indicates that the arrangement order is determined so that the fourth number after the two-digit number “7438525858755” is located at the beginning. Therefore, the head position is shifted so that the head "7" is located at the fourth position from the rear. As a result, "743852588" other than the leading decision key "04"
755 ”(refer to FIG. 9A), the second encrypted data“ 525858755438 ”is obtained as shown in FIG. 9B.

Next, the CPU 23 specifies the permutation determination key (step ST125 in FIG. 8). In the present embodiment, since the permutation determination key is the first four digits of the second encrypted data, in this case, the first four digits “5258” are specified as the permutation determination key. The CPU 23 searches the reference table stored in the hard disk 26, and the permutation determination key is “5258”, and the arrangement order is “32568”.
714 "is read out and stored in the RAM (step ST127 in FIG. 8). Next, the CPU 23 performs a decryption process for the second encrypted data (step ST129). Specifically, it is performed as follows. In this case, “87557438” excluding the permutation determination key “5258” (FIG. 9B).
(See), the order of encryption is such that the third data “8” is originally arranged at the top, the second data “7” is originally arranged at the second, and so on. In other words, the rearrangement is performed such that the first number “3” is originally the first number and the second number is “7”. As a result, the first encrypted data "37885547" can be obtained from the second encrypted data "525858755438" as shown in FIG. 9B.

Next, the CPU 23 identifies the addition key (step ST131 in FIG. 8). In the present embodiment, the addition key is the first four digits of the first encrypted data, so in this case, the CPU 23 causes the addition key “3788”.
To identify.

Next, the decryption processing of the first encrypted data is performed (step ST133 in FIG. 8). Specifically, the latter 4
This is performed by subtracting each number of the addition key "3788" from each number of the digit "5547". In addition, in the encryption process, when the value after addition has two digits, for example, 8 + 9 = 17, only 7 of 17 is stored as the number after addition. Therefore, similar processing may be performed in the case of subtraction. In this way, the CPU 23 on the credit company side ends the decryption process.

The CPU 23 on the credit company side determines whether or not the decrypted personal identification number matches the personal identification number reported in advance (step ST79 in FIG. 4), and transmits the verification result (step ST80). In the present embodiment, either credit OK or non-credit is transmitted as the verification result.

The CPU 23 on the center side repeatedly determines whether or not the collation result is received (step ST43 in FIG. 4). When the collation result is received, it is determined whether the collation result is OK or not (credit OK). Step S
T45). In the case of credit OK, the CP on the user side
The collation result signal of ordering OK is transmitted to U23 (step ST47).

The CPU 23 on the user side repeatedly determines whether or not the collation result signal is received (step ST
15) When the verification result signal is received (step ST1)
7) Determine the type of verification result signal. Credit OK
In the case of, CR will send a message saying "Ordering is completed"
Display at T29.

When the center CPU 23 determines in step ST45 that the credit cannot be accepted as the verification result, the CPU 23 sends a verification result signal indicating that the order is impossible to the CP on the user side.
It transmits to U23 (step ST50). C on the user side
When the PU 23 receives the collation result signal indicating that the order cannot be placed,
An error message "There is an error in the credit information" is displayed on the CRT 29. Furthermore, "Re-enter?" Is displayed, and if there is a re-input command, the processing from step ST1 is repeated. On the other hand, if there is no re-input command, the process ends.

As described above, in this embodiment, since the personal identification number encrypted in a plurality of stages is transmitted and received, the possibility that the personal identification number is known to a third party is reduced.

Regarding the first to third encryption processing,
The encryption process is not limited to the above process, and another encryption process may be used. Further, the addition position of the additional data is not limited to this. Moreover, you may exchange the procedure of the 1st-3rd encryption process.

The personal identification number stored in the hard disk of each terminal of the user has already been encrypted. Therefore, even if the system goes down due to some accident, there is no possibility that the personal identification number remains on the hard disk side. As a result, there is no risk that the personal identification number will be obtained by a third party.

In this embodiment, in order to realize the function shown in FIG. 1, the CPU 23 is used and this is realized by software. However, some or all of them may be realized by hardware such as a logic circuit.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a transmitting device 50 and a receiving device 70 that perform encryption and decryption in a system according to the present invention.

2 is a diagram showing an example of a hardware configuration of a transmission device 50 and a reception device 70 shown in FIG.

[Fig. 3] Each C on the user side, the center side, and the credit company side
The flowchart of the process which PU performs is shown.

[Fig. 4] Each C on the user side, the center side, and the credit company side
The flowchart of the process which PU performs is shown.

FIG. 5 shows a flowchart of encryption processing.

FIG. 6 is a diagram showing an encrypted personal identification number.

FIG. 7 is a diagram showing a reference table.

FIG. 8 is a flowchart of a decoding process.

FIG. 9 is a diagram showing the progress of the decoding process.

FIG. 10 is a conceptual diagram of an online shopping system for using the transmission / reception method of the present invention.

[Explanation of symbols]

 53 ... First encryption means 55 ... Second encryption means 57 ... Third encryption means 59 ... Transmission means 73 ... First decryption means 75 ... Second decryption Means 77 ... Third Decoding Means 79 ... Receiving Means 23 ... CPU 25 ... ROM 27 ... RAM

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Claims (7)

[Claims] 1. A device for transmitting a personal identification number having a predetermined number of digits, wherein the personal identification number is encrypted with a first encryption key, and the first identification key is used.
A first encryption means for generating first encrypted data to which an encryption key is added; encrypting the first encrypted data with a second encryption key,
Second encryption means for generating second encrypted data to which this second encryption key is added, encrypting the second encrypted data with a third encryption key,
A transmitting device comprising: a third encrypting means for generating the third encrypted data to which the third encryption key is added; and a transmitting means for transmitting the third encrypted data. 2. The transmitting apparatus according to claim 1, wherein the first encryption key to the third encryption key are generated by generating random numbers.
A transmitting device characterized by determining an encryption key. 3. The transmission device according to claim 2, wherein the second encryption means has a reference table composed of the second encryption key and rearrangement order determination data corresponding to the second encryption key, When the second encryption key is specified, the second encryption process is performed by referring to this reference table, and the transmitting device is characterized in that. 4. The transmitting device according to claim 3, wherein the personal identification number is a four-digit personal identification number of a credit card, and the first encryption key is composed of four digits.
The encryption means performs the first encryption processing by adding each digit of the first encryption key to the personal identification number, and the second encryption key is composed of four digits. Second
Based on the second encryption key, referring to the reference table, rearranges the digits of the personal identification number to which the first encryption key is added, and the third encryption key has two digits. And the third
The encryption means determines the digit at the head position of the personal identification number to which the first and second encryption keys are added, based on the third encryption key, and sequentially rearranges the digits. Transmitter. 5. A personal identification number encrypted with the first to third encryption keys and having the first to third encryption keys added thereto is received,
A receiving device for performing a decryption process, wherein the receiving means receives a personal identification number to which the first encryption key to the third encryption key are added, and the first encryption key to the third encryption key are added. Identify which of the PINs is the third encryption key,
By decrypting with the third encryption key, the first
And third decryption means for generating a personal identification number to which the second encryption key is added, and which one of the personal identification numbers to which the first and second encryption keys are added is the second encryption key Second decryption means for generating a personal identification number to which the first encryption key is added by decrypting with the second encryption key, of the personal identification number to which the first encryption key is added. The first encryption key to the third encryption key are determined by identifying which is the first encryption key and decrypting with the first encryption key.
The first to generate a personal identification number before it is encrypted with an encryption key
A receiving device comprising: a decoding unit. 6. A method for transmitting a personal identification number having a predetermined number of digits, wherein the personal identification number is encrypted with a first encryption key, and the first identification key is used.
Generating first encrypted data to which an encryption key is added, encrypting the first encrypted data with a second encryption key,
Generating second encrypted data to which the second encryption key is added, encrypting the second encrypted data with the third encryption key,
A transmitting method, comprising: generating third encrypted data to which the third encryption key is added, and transmitting the third encrypted data. 7. A personal identification number encrypted with the first to third encryption keys and having the first to third encryption keys added thereto is received,
A receiving method for performing a decryption process, comprising: receiving a personal identification number to which the first encryption key to the third encryption key are added, and a personal identification number to which the first encryption key to the third encryption key are added. Identify which of these is the third encryption key,
By decrypting with the third encryption key, the first
And a personal identification number to which the second encryption key is added, and which of the personal identification numbers to which the first and second encryption keys are added is the second encryption key, and the second identification key is specified. By decrypting with an encryption key, a personal identification number with the first encryption key is generated, and which of the personal identification numbers with the first encryption key is the first encryption key. By identifying and decrypting with the first encryption key, the first encryption key to the third encryption key
A receiving device characterized by generating a personal identification number before being encrypted by an encryption key.