Data encryption method, recording medium, data transfer apparatus, and encrypted data decryption method

A data encryption method, comprising:

• a first encrypted data generating step for encrypting data through the use of a first encryption key to generate first encrypted data;
• a second encrypted data generating step for encrypting said first encrypted data through the use of a second encryption key to generate second encrypted data;
• a decryption key generating step for generating a first decryption key corresponding to said first encryption key and a second decryption key corresponding to said second encryption key;
• and
• a first electronic watermark embedding step for embedding either said first decryption key or said second decryption key in said second encrypted data as a first form of electronic watermark to generate third encrypted data.

A data encryption method, comprising:

• an encrypted data generating step for encrypting data through the use of an encryption key to generate first encrypted data;
• a decryption key generating step for generating a decryption key corresponding to said encryption key;
• a first electronic watermark embedding step for embedding said decryption key in said first encrypted data as an electronic watermark to generate second encrypted data;
• and
• a step for adding restrictions on decryption based on pass word on said second encrypted data.

An encrypted data decryption method for decrypting encrypted data, comprising:

• a first detection step for detecting a first decryption key from the electronic watermark embedded in said encrypted data;
• a second detection step for detecting a second decryption key to be inputted from an external system;
• and
• a step for decrypting encrypted data through the use of said first and second decryption keys to obtain decrypted data.

An encrypted data decryption method for decrypting encrypted data, comprising:

• a first detection step for detecting a first decryption key from the electronic watermark embedded in said encrypted data;
• a second detection step for detecting a second decryption key to be inputted from an external system;
• a step for decrypting said encrypted data through the use of said first decryption key to obtain first decrypted data;
• and
• a step for decrypting said first decrypted data through the use of said second decryption key to obtain second decrypted data.

An encrypted data decryption method for decrypting encrypted data, comprising:

• a step for inputting a pass word which removes restrictions on decryption of said encrypted data;
• a first detection step for detecting a decryption key from the electronic watermark embedded in said encrypted data;
• and
• a step for decrypting encrypted data through the use of said decryption key to obtain decrypted data.

An encrypted data decryption method for decrypting encrypted data, comprising:

• a first detection step for detecting a first decryption key from a first form of electronic watermark embedded in said encrypted data;
• a second detection step for detecting a second decryption key from a second form of electronic watermark embedded in said encrypted data;
• and
• a step for decrypting encrypted data through the use of said first and second decryption keys to obtain decrypted data.