Method and apparatus for controlling access to encrypted data files in a computer system

(57) In the system which can carry out protection management of the encipherment information by the user of a large number which carry out summary cooperation and use a password, the file containing secret data contains both of data parts enciphered as the header which is not enciphered. A data part is enciphered by a single file key including both of lists of secret data and hashed passwords. The file header which is not enciphered contains two tables. The 1st table is a list of passwords and each password is hashed in code using the 2nd hash technology different from the password hashed by the data part of a file. The 2nd table is a list of the combination hashed like a code of the password hashed in code, combination corresponds to a registered user's selection group, and a password is hashed using the same technology as the password stored in the data part of a file. Each hashed combination is used also as a password key for enciphering a file key in a list. During use of a system, the registered user needs to enter the password which can be discovered on the 1st table, when hashed. If the entered password is discovered on the 1st table, it will be judged whether it checked and sufficient registered user who constitutes a selection group entered the password. When a selection group exists, after selection group's user's password is hashed and can combine with the 1st hash technology, it is hashed further and a password key is formed. A file key is used in order to be decoded by a password key and to decode a file. The hashed password in the protection portion of a file can be used in order to manage a password list.