When a loan is approved for a person or company, the bank is subject to \emph{credit risk}; the risk that the lender defaults. To mitigate this risk, a bank will require some form of \emph{security}, which will be collected if the lender defaults. Accounts can be secured by several securities and a security can be used for several accounts. The goal is to fractionally assign the securities to the accounts so as to balance the risk. This situation can be modelled by a bipartite graph. We have a set S of securities and a set A of accounts. Each security has a \emph{value} viβ and each account has an \emph{exposure} ejβ. If a security i can be used to secure an account j, we have an edge from i to j. Let fijβ be part of security i's value used to secure account j. We are searching for a maximum flow that send at most viβ units out of node iβS and at most ejβ units into node jβA. Then sjβ=ejβββiβfijβ is the unsecured part of account j. We are searching for the maximum flow that minimizes βjβsj2β/ejβ