Protection of Signed Documents Against Unauthorized Modification

Objective

Once a document is signed or certified, protect it so that any later change can be detected.

Guidelines

After a document has been digitally signed or certified:

• Any change to the document must cause the signature validation to fail or clearly show that the document was modified.
• Your system must be able to detect unauthorized changes made after signing.
• No one should be able to add, remove, or change content without that change being detectable.
• It must be possible to verify the document's integrity at any time — today, next month, or years from now.