| 摘要 |
<p>A method is provided for transmitting information having a header portion (242) and a body portion (244), the method includes the steps of providing a clock (80), generating (316) a first key base on the clock (80) and a part of the header portion (242), using the first key for encrypting the body portion (244) to generate an encrypted body portion, combining the encrypted body portion and the header portion to form a data packet (240), combining a video program and the data packet (240) to form and transmit a composite video signal (326). After encryption the encrypted body portion can be scrambled by using a scrambling key to swap the bits of the body portion. A method for receiving transmitted information having a header portion (242) and an encrypted body portion comprises the steps of providing a clock (80), generating (318) a first key based on the clock (80) and a part of the header portion (242), using the first key for decrypting the encrypted body portion to generate a decrypted body portion, combining the decrypted body portion and the header portion to form a data packet, and recording the data packet on a video cassette tape (328).</p> |
