VoVoIP is a standard SIP based VoIP application without PROXY registration and NAT traversal support. Input audio is compressed using the G.729 codec, and then embedded into a G.711 VoIP channel using the least significant bit (LSB) coding. G.729 is an audio data compression algorithm which requires as low as 8kbps to encode human voice - albiet at slightly degraded sound quality. G.711 is an ITU-T standard audio codec primarily used in telephony since the 1970s, and it remains a "must support codec" in today's VoIP world. Regardless of the algorithms used (a-law, u-law), both methods feature 64kbps as their bandwidth requirements due to the 8000Hz frequency and 8-bit resolution per sample. VoVoIP creates a VoIP covert channel by modifying the least significant bit of each sample with G.729 encoded audio, minimizing the loss of cover audio quality. The signaling is handled using a SIP RE-INVITE message with a SDP entry indicating the presence of VoIP covert channel capable codec (100 is given as a RTP payload type). Hence, applications with no VoIP covert channel codec will communicate using the regular G.711 codec with VoVoIP. Generally speaking, attackers prefer hiding the presence of an attack, so it is less likely to see actual VoIP covert channels which utilize SIP for signaling.