KEY MANAGEMENT METHOD AND KEY MANAGEMENT DEVICE

摘要

A key management method and key management device which safely and reliably update the MKBs and the intermediate keys, which are encrypted with an authentication key, of a recording medium. A validity information processing unit (11) refers to validity information (221) in a recording medium (20) and assesses a valid MKB (211) and intermediate key (222), as well as rewrites the validity information (221) when an invalid MKB (211) and intermediate key (222) are rewritten. The MKB processing unit (12) reads the valid MKB (211) and updates an MKB (101), as well as rewrites the invalid MKB (211). The intermediate key processing unit (13) reads the valid intermediate key (222) and decrypts and re-encrypts the valid intermediate key (222) with the authentication key (103), as well as rewrites that invalid intermediate key (222) into the re-encrypted intermediate key.