Abstract: A method of securing transmission of streaming media by encrypting each packet in the stream with a packet key using a fast encryption algorithm. The packet key is a hash of the packet tag value and a closed key which is unique for each stream. The closed key is itself encrypted by the sender and passed to the recipient using a public key encryption system. The encrypted closed key (open key) may conveniently be inserted into the stream header. All of the packets in the stream are encrypted, but only the data pay load of each packet is encrypted. It is computationally infeasible, without knowing the recipient's private key to calculate the closed key based upon knowledge of publicly accessible information such as the recipient's public key, the open key, the encrypted stream data or the packet tag values.

Abstract: A key or licence management system for the secure online distribution of digitized audio-visual works (“media”) using encryption techniques. Encrypted media is stored on a media server while the encryption keys are stored on a media key server. Users acquire rights from online retailers to obtain from the media key server keys corresponding to the media they wish to play. The key server encrypts keys before releasing them, preferably with the user's public key using a public key encryption algorithm. Keys are stored in volatile memory at the user's client device and thus the user is in receipt of the key just in time to play the media.