Method and device for data encrypting

1. A method of encrypting data transmitted from a first device to a second device, performed by using an Advanced Encryption Standard (AES) encryption algorithm, the method comprising:

obtaining size information of an encryption key and size information of data that is to be encrypted and includes a plurality of bits;

encrypting a first bit group among the plurality of bits, by using the encryption key, the first bit group including at least one bit and corresponding to a size of the encryption key;

selecting a third bit group, which includes at least one bit of the encrypted first bit group and is based on the size of the encryption key and a size of a second bit group, among the plurality of bits, which includes bits that are different from the at least one bit in the first bit group; and

encrypting the second bit group and the selected third bit group, by using the encryption key, wherein

the encryption key is changed to a predetermined size, smaller than a size of the data to be encrypted, if the size of the encryption key is greater than the size of the data to be encrypted.

2. The method of claim 1 , further comprising transmitting at a time a first encryption group corresponding to the encrypted first bit group, from which the third bit group is excluded, and a second encryption group, in which the second bit group and the third bit group are merged, to the second device.

3. The method of claim 2 , wherein the transmitting comprises transmitting a group in which the first encryption group and the second encryption group are merged, for every predetermined period.

4. The method of claim 1 , further comprising transmitting encryption group information including information about the selected third bit group, to the second device.

5. The method of claim 1 , further comprising determining whether a size of the data to be encrypted is a multiple of the size of the encryption key.

6. The method of claim 1 , wherein a size of the third bit group is identical to a difference between the size of the encryption key and the size of the second bit group.

7. A device for encrypting data by using an Advanced Encryption Standard (AES) encryption algorithm, the device comprising processing circuitry configured to:

obtain size information of an encryption key and size information of data that is to be encrypted and includes a plurality of bits; and

encrypt a first bit group among the plurality of bits, by using the encryption key which is at least one bit corresponding to a size of the encryption key, among the plurality of bits, by using the encryption key, selecting a third bit group, which is at least one bit of the encrypted first bit group, based on size information of the encryption key and a size of a second bit group including bits that are different from the first bit group, among the plurality of bits, and encrypting the second bit group and the selected third bit group by using the encryption key, wherein

the encryption key is changed to a predetermined size, smaller than a size of the data to be encrypted, if the size of the encryption key is greater than the size of the data to be encrypted.

8. The device of claim 7 , further comprising communication circuitry configured to transmit at a time a first encryption group corresponding to the encrypted first bit group, from which the third bit group is excluded, and a second encryption group in which the second bit group and the third bit group are merged.

9. The device of claim 8 , wherein the communication circuitry is configured to transmit at a time a group in which the first encryption group and the second encryption group are merged, for every predetermined period.

10. The device of claim 7 , further comprising communication circuitry configured to transmit encryption group information including information about the selected third bit group.

11. The device of claim 7 , wherein the processing circuitry is configured to determine whether a size of the data to be encrypted is a multiple of the size of the encryption key.

12. The device of claim 7 , wherein a size of the third bit group is identical to a difference between the size of the encryption key and the size of the second bit group.

13. A non-transitory computer-readable recording medium having embodied thereon a program which, when executed by a processor of a device for encrypting data by using an Advanced Encryption Standard (AES) encryption algorithm, controls the device to perform operations comprising:

obtaining size information of an encryption key and size information of data that is to be encrypted and includes a plurality of bits;

encrypting a first bit group, which is at least one bit corresponding to a size of the encryption key, among the plurality of bits, by using the encryption key;

selecting a third bit group, which is at least one bit of the encrypted first bit group based on size information of the encryption key and a size of a second bit group including bits that are different from the first bit group among the plurality of bits; and

encrypting the second bit group and the selected third bit group by using the encryption key, wherein

the encryption key is changed to a predetermined size, smaller than a size of the data to be encrypted, if the size of the encryption key is greater than the size of the data to be encrypted.