Systems and methods for delivering specific contents to specific recipients using broadcast networks. The methods include receiving an AV signal of a broadcast program and supplementary content which contains a tag identifying a specific recipient and specific contents. The specific contents are encrypted with a public key associated with the specific recipient. The supplementary content is combined with the AV signal to form a data-augmented signal which is subsequently encoded and modulated with a carrier signal to form a transmit signal for broadcasting to receivers. Each receiver includes a supplementary decoder for extracting the supplementary content, decrypting the specific contents with a private key corresponding to the public key, and providing the decrypted specific contents to the intended recipient.