Explain why changing a document after it has been signed should cause verification with the original signature to fail.

### Why this is right A signature is tied to the document’s contents through a hash. When the contents change, the hash calculated during verification differs from the one associated with the original signature, so the check should fail. ### The concept A **hash** is a compact value calculated from data. In the described workflow, it represents the document’s contents for the signature operation. The sender signs using a private key, and the recipient verifies using the corresponding public key. If the document is edited, even if the change appears small, its content no longer matches what was signed. That is why verification detects alteration. The signature does not prevent editing; it helps reveal that editing occurred. ### What a good answer covers - The document is processed to calculate a hash. - The signature is associated with the document through that hash. - A changed document produces a different hash. - The original signature should not verify against the changed document. ### Terms - **Hash**: A compact value calculated from data. - **Verification**: Checking whether a signature is valid for a document and key. - **Integrity**: The condition of data remaining unchanged. ### Remember A signature detects a change by checking whether the document still matches what was signed.