File management apparatus

A file encryption apparatus that encrypts a plaintext to generate a ciphertext and stores the ciphertext into a memory unit thereof, the file management apparatus comprising:

• a key storage medium storing key information beforehand;
• registration means for receiving an input of a password, encrypts the key information using the received password to generate an encrypted key, and writes the generated encrypted key to the memory unit;
• and
• encryption means for encrypting a plaintext using a file key to generate a ciphertext, encrypting the file key using the key information to generate an encrypted file key, and writing the ciphertext in association with the encrypted file key, to the memory unit.

A file management apparatus that encrypts a plain text to generate a ciphertext, stores the ciphertext, and decrypts the ciphertext, the file management apparatus comprising:

• a key storage medium storing key information beforehand;
• registration means for encrypting a password using the key information to generate an encrypted password;
• encryption means for encrypting a plaintext using a file key to generate a ciphertext, encrypting the file key based on a password obtained by decrypting the encrypted password to generate a first encrypted file key, and encrypting the file key based on the key information to generate a second encrypted file key;
• switch means for switching between (a) decrypting the first encrypted file key based on the password and (b) decrypting the second encrypted file key based on the key information, to generate a file key;
• and
• decryption means for decrypting the ciphertext using the generated file key.

A file encryption apparatus that encrypts a plaintext to generate a ciphertext and stores the ciphertext in a memory unit thereof, the file encryption apparatus comprising:

• a key storage medium storing key information beforehand;
• registration means for receiving an input of a password, encrypts the received password using the key information to generate an encrypted password, and writes the generated encrypted password to the memory unit;
• and
• encryption means for decrypting the encrypted password using the key information to generate a password, encrypts a plaintext using a file key to generate a ciphertext, encrypts the file key using the password to generate a first encrypted file key, encrypts the file key using the key information to generate a second encrypted file key, and writes the ciphertext in association with the first encrypted file key and the second encrypted file key, to the memory unit.