In some auction schemes, a seller might need to enter some secret data into the secure marketplace. For example, a seller might want to specify a lower limit below which he does not want to sell the goods. Bidders are allowed to know that such a lower limit exists but cannot know what exactly the lower limit is. In this case, the seller can input its secret data encrypted with the SAM's public key which is dedicated to encryption, or establish a shared secret with SAM to encrypt its secret data. The seller strategy needs to be authenticated to make sure that it comes from the seller. One solution could be that the seller's public key is included in the advertisement of the auction and the seller signs its secret data with its private key before it is encrypted with the SAM's public key.
Similar to the strategy specification language mentioned before, sellers can also specify their strategy or meta-strategy of selling in the strategy specification language. And the same security concerns also apply here.
The seller may include a pledge (or actual digital cash) with the offer to sell; the advertised auction spec will indicate how that pledge is to be disposed of should various bad things (such as the seller not actually producing the item to be sold) occur.