A method for runtime integrity check, performed by a security core including one or more processors includes storing a first output value, which is generated by using a one-way encryption algorithm based on first data and a first encryption key managed by an encryption key manager accessible by the security core, in a main memory that is a volatile memory in association with the first data, generating a second output value for the first data based on the first data and the first encryption key by using the one-way encryption algorithm, and checking for possible tampering of the first data stored in the main memory by comparing the first output value with the generated second output value.