Cryptographic algorithms perform encryption operations using an encryption key to protect information, and process decryption is performed only upon authorization to determine the information. However, when there is vulnerability during the key distribution process, a key life cycle with a certain cryptoperiod can provide a basis for an attack target point. Accordingly, this paper proposes a method to have a different cryptoperiod every time the key is created, making it difficult to determine the key distribution time easily. The cryptoperiod in this study has the nonce property and is defined by the maximum key use count instead of time period, which is generally used. In addition, this study proposes a method that prevents side-channel attack using DErived Key per Access for Real Time (DEKART) derived using a cryptoperiod counter (CC) during communication security that employs a symmetric key. This method, which performs encryption and decryption by generating DEKART whenever it approaches the key, can obtain the same effect of using a new key in every encryption and decryption operation. Thus, it is more secure than the masking technique, which is widely used in side-channel attack prevention in general. In addition, it ensures that the cryptoperiods of the originator and recipient are not different and the DEKART value is not mismatched through the synchronization process of the secured CC value. Furthermore, this study verified that the security performance was improved when DEKART was used compared with the experiment that measured the minimum number of plaintexts required during the chosen-plaintext attack (CPA). Moreover, the comparison results after implementing encryption and decryption operations using a secret key and DEKART showed that if the data size was 10 MB, the operation was slower by 72μs on average in encryption and by 414μs on average in the decryption when using DEKART than when using a secret key, which verified that there was no significant difference in the operation speed between them.

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