Encryption key management method in data subscription system

An apparatus for providing a data subscription service managing an encryption key suitable for providing content data received from a supplier terminal to at least one subscriber terminal based on a subscription application, comprising:

• at least one processor;
• and
• a memory storing instructions executable by the at least one processor and, when executed by the at least one processor, causing the at least one processor to:
• receive a data registration request of content data from the supplier terminal, determine a data identifier (DataID) associated with the content data, encrypting a master key (MK) with a public key of the supplier terminal, and provide the supplier terminal with the master key encrypted with the public key of the supplier terminal, the data identifier, and a key update count value (cnt) to enable the supplier terminal to decrypt the master key encrypted with the public key of the supplier terminal and derive a symmetric key based on the master key (MK), the data identifier (DataID), and the key update count value (cnt);
• receive a subscription application related to the data identifier (DataID) from a first subscriber terminal, encrypt the master key with a public key of the first subscriber terminal, and provide the first subscriber terminal with the master key encrypted with the public key of the first subscriber terminal and the key update count value to enable the first subscriber terminal to decrypt the master key encrypted with the public key of the first subscriber terminal and derive the symmetric key based on the master key (MK), the data identifier (DataID), and the key update count value (cnt);
• receive encrypted content data encrypted with the symmetric key and a hash for the content data from the supplier terminal, decrypt the encrypted content data, and verify the content data using the hash;
• and
• transmit the encrypted content data and the hash to the first subscriber terminal to enable the first subscriber terminal to decrypt the encrypted content data, verify the content data using the hash, and use the content data.