Supply chain interactions have huge economic importance, yet these interactions are managed inefficiently. One of the major sources of inefficiency in supply-chain management is information asymmetry; i.e., information that is available to one or more organizations in the chain (e.g., manufacturer, retailer) is not available to others. There are several causes of information asymmetry, among them fear that a powerful buyer or supplier will take advantage of private information, that information will leak to a competitor, etc. We propose Secure Supply-Chain Collaboration (SSCC) protocols that enable supply-chain partners to cooperatively achieve desired system-wide goals without revealing the private information of any of the parties, even though the jointly-computed decisions require the information of all the parties. Secure supply-chain collaboration has the potential to improve supply-chain management practice, and, by removing one major inefficiency therein, improve productivity. We present specific SSCC protocols for two types of supply-chain interactions: Capacity allocation, and e-auctions. In the course of doing so, we design techniques that are of independent interest, and are likely to be useful in the design of future SSCC protocols.