A method for establishing shared information is described. The method includes estimating characteristics of a communication channel between two nodes based on signals transmitted between the nodes. The method also includes transmitting a signal from the first node to the second node, the signal being modulated with a first data sequence according to a first estimated characteristic, and transmitting a signal from the second node to the first node, the signal being modulated with a second data sequence according to a second estimated characteristic. Shared information is formed at each of the first and second nodes based on at least a portion of the first data sequence and at least a portion of the second data sequence.