Method and system for communicating homomorphically encrypted data

1. A method for communicating encrypted data between an electronic device and a server, the method comprising:

receiving, by a communication interface including communication circuitry, of the electronic device, first data inputted from a user;

generating, by a processor, a query related to the first data;

homomorphically encrypting, by the processor, the query;

transmitting, by the communication interface, the homomorphically-encrypted query to the server;

receiving second data corresponding to the homomorphically-encrypted query from the server, wherein the second data is homomorphically-encrypted data;

generating, by the communication interface, third data by decrypting the second data; and

displaying, by a display of the electronic device, the third data.

2. The method of claim 1 , further comprising, prior to generating the query related to the first data:

generating, by the processor, ciphertexts by homomorphically-encrypting one or more plaintexts using a public key; and

transmitting, by the communication interface, the ciphertexts to the server.

3. The method of claim 2 , wherein receiving the second data corresponding to the homomorphically-encrypted query comprises:

receiving, by the communication interface, as the second data, at least a part of the ciphertexts transmitted to the server.

4. An electronic device for communicating encrypted data with a server, the electronic device comprising:

a display;

a communication interface comprising communication circuitry; and

a processor comprising processing circuitry, the processor configured to:

if first data is inputted from a user, generate a query related to the first data,

homomorphically encrypt the query,

control the communication interface to transmit the homomorphically-encrypted query to the server,

control the communication interface to receive second data corresponding to the homomorphically-encrypted query from the server, wherein the second data is homomorphically-encrypted data,

generate third data by decrypting the second data, and

control the display to display the third data.

5. The electronic device of claim 4 , wherein the processor is further configured to:

generate ciphertexts by homomorphically-encrypting one or more plaintexts using a public key, and

control the communication interface to transmit the ciphertexts to the server.

6. The electronic device of claim 5 , wherein the communication interface is configured to receive, as the second data, at least a part of the ciphertexts transmitted to the server.

7. A method for communicating encrypted data between a server and an electronic device, the method comprising:

receiving, by a communication interface comprising circuitry of the server, a homomorphically-encrypted query from the electronic device;

converting, by a processor of the server, the homomorphically-encrypted query into a logic for searching for first data corresponding to the homomorphically-encrypted query, based on a command included in the homomorphically-encrypted query;

determining, by the processor, the first data satisfying the logic, wherein the first data is homomorphically-encrypted data; and

transmitting, by the communication interface, the first data to the electronic device,

wherein the first data is decrypted by the electronic device and displayed on a display of the electronic device.

8. The method of claim 7 , further comprising, prior to receiving the homomorphically-encrypted query from the electronic device,

receiving, by the communication interface, a public key from the electronic device and storing the public key.

9. The method of claim 7 , further comprising, prior to receiving the homomorphically-encrypted query from the electronic device,

receiving, by the communication interface, ciphertexts into which one or more plaintexts are homomorphically-encrypted by the electronic device using the public key, and storing the ciphertexts.

10. The method of claim 7 , wherein if the homomorphically-encrypted query is used to determine whether two values included in the decrypted first data match each other, the determination is made by:

equal( x , y )=Π i=0 μ−1 (1+ x i + y i )

where i and (μ−1) are natural numbers, the determination outputs 1 if x and y are the same as each other, and outputs 0 if x and y are different from each other, x and y are integers, x and y are encrypted values of x and y, x i represents an i th bit of x, y i represents an i th bit of y, x l , represents an encrypted value of x i , and y i represents an encrypted value of y i .

11. The method of claim 7 , wherein if the homomorphically-encrypted query is used to determine a greater value between two values included in the decrypted first data, the determination of the greater value between the two values is made using:

comp( x , y )= c μ−1 , where

c i =(1+ x i )· y i +(1+ x i + y i )· c i−1 for i ≥ 1

c 0 =(1+ x 0 )· y 0 for i =0

where i and (μ−1) are natural numbers, the determination outputs a greater value between x and y included in the decrypted first data, x and y are integers, x and y are encrypted values of x and y, x i represents an i th bit of x, y i represents an i th bit of y, x i represents an encrypted value of x i , and y i represents an encrypted value of y i .

12. The method of claim 7 , wherein if the homomorphically-encrypted query is used to add at least two values included in the decrypted first data, a determination of a sum of the at least two values is made using:

fadd υ( x , y )=( s o , s 1 , . . . . . . , s υ−1 ), where

s i = x i + y i + c i−1 and

c i =( i · y i )+(( i + y i )· c i−1 ) for i ≥ 1,

s 0 = x 0 + y 0 and c 0 = x 0 · y 0

where i and (υ−1) are natural numbers, the determination outputs a sum of x and y included in the decrypted first data, x and y are integers, x and y are encrypted values of x and y, x i represents an i th bit of x, y i represents an i th bit of y, x i represents an encrypted value of x i , and y i represents an encrypted value of y i .