I am familiar with PKI and signing one document (for instance XML content) using PKCS7 or XAdES and we provide this functionality to our customer. Works fine. I now wonder how to facilitate the signing of a set of documents, that is signing the whole folder (set of documents) with one signature. The set can be viewed as a main document and some attachments.
My idea is to build an XML file including references to each document. The reference could be the hash of the document (value and algorithm). The customer will sign this XML file (like before with our RSA PKI).
- What do I break in my new mechanism where I add this level of indirection (we sign in fact something like a manifest and not the data)
- What is the legal value of this? Maybe we lost the integrity of the signature, and we break the non repudiation.
- Shall we validate (certify) our process (XML generation and keep the links of references) to a third party to guarantee the non repudiation?
- How can I exploit the signature? I think I can't show to the customer that he/she has signed only one attachment. I always need to show the whole folder.
- Shall I be aware of some points I forgot here? What do you think of my new mechanism?