In P2P networks, an economic measure is efficient to incentivize nodes to provide services to others. As the payment scheme is essential in the economic measure, an efficient and reliable payment scheme is our goal. In this paper, we propose a mechanism that the peers. transfer a file in pieces, and the length of the piece may be 1 MBytes. After getting one piece, 'the downloader pays an electronic check to the source node. The amount of tokens in the electronic check is for one piece of the file that the source node has just sent to the downloader. The electronic check is signed by the payer's private key and can be redeemed into tokens by the payee. As the transferred unit is one file piece, even if the source node fails during transaction, the downloader can resume downloading from other nodes. As a result the payment scheme can counterwork the accidents. Furthermore, our economic framework can well handle the inflation, the deflation, the sybil attack and the cheating, and is well adaptive to P2P dynamic environment. Therefore, the economic framework is reliable in P2P networks.
