System for securely communicating information packets

1. A system for securely transmitting Real Time Protocol voice packets during a communication session with a remote multimedia terminal adapter over an Internet protocol network, the system comprising:

a local multimedia terminal adapter receiving the voice packets having a time stamp synchronization source operable to synchronize cryptographic operations between said local multimedia terminal adapter and said remote multimedia terminal adapter, the local multimedia terminal adapter comprising,

a local key stream generator for generating a first key stream; and

a packet encryptor that encrypts the voice packets using at least a portion of the first key stream to form encrypted voice packets;

the remote multimedia terminal adapter receiving the encrypted voice packets, the remote multimedia terminal adapters further comprising,

a remote key stream generator for generating the first key stream in order to decrypt the encrypted voice packets; and

a packet decryptor decrypting the encrypted voice packets using the first key stream, wherein both key stream generators generate a second key stream when a component used to transmit the Real Time Protocol voice packets changes during the communication session and the packet encryptor and packet decryptor use the second key stream, wherein

the second key stream is generated when the system switches from a first to a second coder/decoder for compression/decompression of the voice packets.

2. The system of claim 1 wherein the second key stream is generated when a Message Authentication Code algorithm change occurs.

3. The system of claim 1 further comprising a local gateway controller for forwarding the encrypted packets through the Internet protocol network.

4. The system of claim 1 further comprising a remote gateway controller for receiving the encrypted packets from the Internet protocol network and for forwarding encrypted voice packets to the remote multimedia terminal adapter.

5. A system for communicating Real Time Protocol voice packets between a local and a remote location over an Internet protocol network, the system comprising:

a stream cipher module for encrypting the voice packets; and

a key stream generator device for generating a first Real Time Protocol key stream, the stream cipher module employing the first key stream to encrypt the voice packets for forwarding to the remote location, the key stream generator device producing a second Real Time Protocol key stream for encrypting the voice packets when the system switches from a first communication parameter to a second communication parameter, each of the first and second parameters being involved in the synchronization of the key stream, wherein the voice packets have a time stamp synchronization source operable to synchronize cryptographic operations between said local and remote locations, wherein the first communication parameter is a first coder/decoder that compresses/decompresses the voice packets, and the second communication parameter is a second coder/decoder that compresses/decompresses the voice packets.

6. The system of claim 5 further comprising a new time tamp sequence generated when the second Real Time Protocol key stream is generated.

7. The system of claim 5 wherein the second key stream is generated by re-executing the following key derivation function:

F(S, “End-End RTP Key Change <N>”) where:

N is a counter incremented whenever a new set of Real Time Protocol keys is re-derived for the same media stream session;

F( ) is a one-way pseudo-random function used for the purpose of key derivation;

S is a shared secret which includes a random value shared between the two endpoints and is known only to those two endpoints or a trusted server; and

“End-End RTP Key Change <N>” is a label that is used as a parameter to the key derivation function F( ), <N> stands for an ASCII representation of a decimal number, representing a counter.

8. The system of claim 5 wherein the second key stream is generated by re-executing the following key derivation function:

F(S, SSRC, “End-End RTP Key Change <N 22 ”) where:

S is a shared secret which includes a random value shared between the two endpoints and is known only to those two endpoints or a trusted server;

SSRC is the synchronization source session identifier;

N is the counter of the number of key changes for the same SSRC value; and

“End-End RTP Key Change <N>” is a label that is used as a parameter to the key derivation function F( ), <N> stands for an ASCII representation of a decimal number, representing a counter.

9. A system for securely transmitting voice packets during a communication session from a local location to a remote location over a communication network, the system comprising:

a means for generating a first key stream at the local location;

a means for encrypting the voice packets using at least a portion of the first key stream to form encrypted voice packets;

a means for forwarding the encrypted voice packets from the local location to the remote location;

a means for generating the first key stream at the remote location in order to decrypt the encrypted voice packets; and

a means for decrypting the encrypted voice packets using the first key stream, wherein both means for generating are capable of generating a second key stream when a component used to transmit the Real Time Protocol voice packets changes during the communication session, wherein the voice packets have a time stamp synchronization source operable to synchronize cryptographic operations between said local and remote locations,

wherein the second key stream is generated when the system switches from a first to a second coder/decoder for compression/decompression of the voice packets.

10. The system of claim 9 wherein the second key stream is generated by re-executing the following key derivation function:

F(S, “End-End RTP Key Change <N>”) where:

N is a counter incremented whenever a new set of Real Time Protocol keys is re-derived for the same media stream session;

F( ) is a one-way pseudo-random function used for the purpose of key derivation;

S is a shared secret which includes a random value shared between the two endpoints and is known only to those two endpoints or a trusted server and

“End-End RTP Key Change <N>” is a label that is used as a parameter to the key derivation function F( ), <N> stands for an ASCII representation of a decimal number, representing a counter.

11. The system of claim 9 wherein the second key stream is generated by re-executing the following key derivation function:

F(S, SSRC, “End-End RTP Key Change <N>”) where:

S is a shared secret which includes a random value shared between the two endpoints and is known only to those two endpoints or a trusted server;

SSRC is the synchronization source session identifier;

N is the counter of the number of key changes; and

“End-End RTP Key Change <N>” is a label that is used as a parameter to the key derivation function F( ), <N> stands for an ASCII representation of a decimal number, representing a counter.

12. The system of claim 9 further comprising a means for synchronizing the voice packets.