We consider a pair-wise independent network where every pair of terminals in the network observes a common pair-wise source that is independent of all the sources accessible to the other pairs. We propose a method for secret key agreement in such a network that is based on well-established point-to-point techniques and repeated application of the one-time pad. Three specific problems are investigated. 1) Each terminal's observations are correlated only with the observations of a central terminal. All these terminals wish to generate a common secret key. 2) In a pair-wise independent network, two designated terminals wish to generate a secret key with the help of other terminals. 3) All the terminals in a pair-wise independent network wish to generate a common secret key. A separate protocol for each of these problems is proposed. Furthermore, we show that the protocols for the first two problems are optimal and the protocol for the third problem is efficient, in terms of the resulting secret key rates.