1. A data encryption and decryption method using a symmetric cryptographic algorithm, comprising: once it is determined that S boxes are needed to be used to perform table lookup in the symmetric cryptographic algorithm, determining types of all S boxes needed to be used; for each type of S boxes, determining a total number N i of S boxes of the type, and in a case that N i is greater than 1, determining that a reusing condition is satisfied for the type of S boxes; and reusing at least one type of S boxes, for which the reusing condition is satisfied, in the data encryption and decryption using the symmetric cryptographic algorithm.