When a peer in a public network needs to open a connection to another one being behind network address translator it encounters the network address translation problem. The approach called "UDP hole punching" allows opening a public-to-private or private-to-private network connection. This article deals with this approach to propose new security architecture for IPv4 communication introducing so called "implicit security" concept. Key benefits it brings are ability to interconnect to any host behind NAT using just a host?s domain name, and encryption and authentication of all data transmitted through this connection right from a packet sender to a local receiver. Secure channel is established on-demand automatically and is independent on any application. No additional modification of current NAT, IPv4 or DNS is required.