Method for encrypting and embedding information in a video program

A method for decrypting information in a composite video signal having an embedded header portion and an encrypted body portion, the method comprising the steps of:

• reading a current month from a clock having an output as a function of time;
• extracting an odd/even month indication from the header portion;
• generating a first key based on the current month read from the clock if the odd/even indication is odd and the current month read from the clock is odd or if the odd/even indication is even and the current month read from the clock is even, otherwise generating the first key based on a month previous to the current month read from the clock if the odd/even indication is odd and the current month read from the clock is even or if the odd/even indication is even and the current month read from the clock is odd;
• and
• using the first key for decrypting the encrypted body portion to generate a decrypted body portion.

An apparatus for encrypting information having a header portion and a body portion, the apparatus comprising:

• a clock having an output as a function of time;
• means for reading a current month from the clock;
• means for setting an odd/even month indication in the header portion to odd, if the current month read from the clock is an odd month, otherwise, setting an odd/even month indication in the header portion to even, if the current month read from the clock is an even month;
• means for generating a first key based on the current month read from the clock if the odd/even indication is odd and the current month read from the clock is odd or if the odd/even indication is even and the current month read from the clock is even, otherwise generating the first key based on a month previous to the current month read from the clock if the odd/even indication is odd and the current month read from the clock is even or if the odd/even indication is even and the current month read from the clock is odd;
• means for encrypting the body portion using the first key to generate an encrypted body portion;
• and
• means for embedding the encrypted body portion and the header portion within a video signal to form a composite video signal.

An apparatus for decrypting information having a header portion and an encrypted body portion embedded in a composite video signal, the apparatus comprising:

• a clock having an output as a function of time;
• means for reading a current month from the clock;
• means for extracting an odd/even month indication from the header portion;
• means for generating a first key based on the current month read from the clock if the odd/even indication is odd and the current month read from the clock is odd or if the odd/even indication is even and the current month read from the clock is even, otherwise generating the first key based on a month previous to the current month read from the clock if the odd/even indication is odd and the current month read from the clock is even or if the odd/even indication is even and the current month read from the clock is odd;
• and
• means for using the first key for decrypting the encrypted body portion to generate a decrypted body portion.

A method for encrypting and sending information having a header portion and a body portion and for decrypting the received information comprising the steps of:

• reading a first current month from a first clock having an output as a function of time;
• setting an odd/even month indication in the header portion to odd, if the first current month read from the first clock is an odd month, otherwise, setting an odd/even month indication in the header portion to even, if the first current month read from the first clock is an even month;
• generating a first key based on the first current month read from the first clock if the odd/even indication is odd and the first current month read from the first clock is odd or if the odd/even indication is even and the first current month read from the first clock is even, otherwise generating the first key based on a month previous to the first current month read from the first clock if the odd/even indication is odd and the first current month read from the first clock is even or if the odd/even indication is even and the first current month read from the first clock is odd;
• using the first key for encrypting the body portion to generate an encrypted body portion;
• embedding the encrypted body portion and the header portion within a video signal to form a composite video signal;
• transmitting the composite video signal;
• receiving the transmitted composite video signal;
• reading a second current month from a second clock having an output as a function of time;
• extracting an odd/even month indication from the received header portion;
• generating a second key based on the second current month read from the second clock if the odd/even indication is odd and the second current month read from the second clock is odd or if the odd/even indication is even and the second current month read from the second clock is even, otherwise generating the second key based on a month previous to the second current month read from the second clock if the odd/even indication is odd and the second current month read from the second clock is even or if the odd/even indication is even and the second current month read from the second clock is odd;
• and
• using the second key for decrypting the received encrypted body portion to generate a decrypted body portion.