Data recording apparatus, data recording method, and data transfer system

A data recording method for recording a desired piece of encrypted content data selected from among a plurality of pieces of encrypted content data recorded to a primary recording medium to a secondary recording medium which is different from said primary recording medium, said data recording method comprising the steps of:

• firstly receiving an enabling key block for restoring a root key of a hierarchical key group transmitted from said primary recording medium;
• searching for said root key on the basis of any one of device node keys composed of a lowest hierarchical key stored in an internal memory of a recording apparatus capable of accommodating said secondary recording medium and said hierarchical key group encrypted by use of said lowest hierarchical key, and said received enabling key block;
• secondly receiving encrypted content data from said primary recording medium after the searching for said root key;
• decrypting said encrypted content data received in said second receiving step;
• recording said content data decrypted in said decrypting step to said secondary recording medium;
• determining whether said enabling key block of said desired piece of encrypted content data selected from said plurality of pieces of encrypted content data recorded to said primary recording medium is common to an enabling key block of a desired piece of encrypted content data previously recorded from said primary recording medium to said secondary recording medium;
• and
• controlling to skip said first receiving step and said searching step, if said enabling key block of said desired piece of encrypted content data selected from said plurality of pieces of encrypted content data recorded to said primary recording medium is found common in said determining step.

A data transfer system for transferring a desired encrypted piece of content data selected from a plurality of pieces of content data recorded to a primary recording medium to a secondary recording medium which is different from said primary recording medium, said data transfer system comprising:

• reception means for receiving said encrypted content data generated for said selected desired piece of content data transmitted from said primary recording medium and an enabling key block for restoring a root key for a hierarchical key group;
• storage means for storing device node keys composed of a lowest hierarchical key set for said data recording apparatus for recording said desired piece of content data to said secondary recording medium and said hierarchical key group encrypted by said lowest hierarchical key;
• restoration means for restoring said root key by use of said enabling key block received by said reception means and any one of said device node keys stored in said storage means;
• confirmation means for confirming a version of said enabling key block received by said reception means;
• and
• prohibition means for preventing said root key from being restored redundantly by said restoration means, if said enabling key block of said selected desired piece of content data is found common in version to a previous enabling key block by said confirmation means.