Patent ID: 7747013

Claim:
A method of providing in-band early encryption detection within a packet data network for telephony calls, the method comprising: prior to receiving a signalling message indicating a mode of operation of a transmitter end of said packet data network, receiving, at a receiver end of said packet data network, a plurality of voice stream packets; determining whether encryption capabilities of said receiver end and a transmitter end match, said determining comprising: determining whether at least one of said voice stream packets includes a predetermined pattern inserted into said packet at said transmitter end of said packet data network; upon finding said predetermined pattern in said at least one of said voice stream packets, determining that said voice stream packets are unencrypted and changing a cipher to non-decryption mode prior to delivering said voice stream packets; upon finding no said predetermined pattern in said at least one of said voice stream packets, decrypting said packet with a pre-configured cipher and further determining whether said decrypted packet includes said predetermined pattern; upon finding said predetermined pattern in said decrypted packet, determining that said voice stream packets are encrypted and that the pre-configured cipher at the receiver end matches a cipher at the transmitter end, changing said cipher to decryption mode, and decrypting subsequent packets in said voice stream packets prior to delivering said decrypted voice stream packets; and upon finding no said predetermined pattern, discarding said decrypted packet and processing another one of said voice stream packets from said receiving step.