Abstract: A method of and an apparatus for copying and decrypting encrypted digital data. The method of copying encrypted digital data includes encrypting a first media key block to be used for decryption of the encrypted digital data using a predetermined key of a second information storage medium and storing the encrypted digital data and the encrypted first media key block in the second information storage medium. Security of data encryption is heightened by not discarding an encryption key used for an initial encryption, encrypting the encryption key used for initial encryption using another encryption key used for a second encryption, and storing the encrypted encryption key with the data. Also, since unnecessary decryption and encryption of data are not repeated, the time required for copying data is reduced, and since data is transferred between apparatuses in an encrypted state, a security level is higher.