| 摘要 |
PROBLEM TO BE SOLVED: To construct security at higher level in preservation of encrypted data.SOLUTION: The present invention relates to a construction method for security in data preservation including encryption and decryption of data. The encryption in a device includes the steps of: using a data encryption/decryption algorithm (8) to generate ciphertext (9) with plaintext data (1) as key data (0); using a first key encryption/decryption algorithm (2) to perform random processing on the plaintext key data (0) with first password data (3) as a key, and encrypting the plaintext data (0) to generate first key ciphertext (4); and using a second key encryption/decryption algorithm (5) to at least double encrypting the first key ciphertext (4) with second password data (6) which are different from the first password, as a key to generate second key ciphertext (7). The decryption in the device is performed in reverse order of the steps. The second password is related to eigen information for each of quipment included in the device itself, thereby improving a strength of the security.SELECTED DRAWING: Figure 2 |
