Abstract: A storage centered transaction and authentication model (SCTAM) is proposed with all information stored in transaction center (TC) where operations are carried out automatically and information security and consistency are ensured. The user does not interact with the owner in transaction; the judge can make decision without the aids from the owner and the user, which is fairer. Different watermark techniques are used to embed and extract watermarks for the owner and for the user to ensure the security of the watermarks. SCTAM can settle all problems discovered so far and make watermarking protocol easy to implement.