Tamper-Evident Seal
A tamper-evident seal is a cryptographic mechanism embedded in a signed document that causes verification to fail if the document's content is modified after signing, providing visible proof of any tampering.
What it means
In PDF documents, the tamper-evident seal is implemented through the digital signature standard: the signature covers a cryptographic hash of the document's byte ranges. Most PDF viewers (including Adobe Acrobat) will display a prominent warning banner if a signed document has been altered. This is distinct from document encryption — a tamper-evident seal does not prevent reading the document, only undetected modification.
Why it matters for e-signatures
Every completed SignOwl document carries a tamper-evident seal. This lets you share signed contracts with confidence — any recipient can verify the document is exactly as signed, and any tampering attempt is immediately visible.
Related terms
Frequently asked questions
Is a tamper-evident seal the same as password protection?
No. Password protection controls who can open or edit a document. A tamper-evident seal allows anyone to open and read the document but makes unauthorized modifications detectable.
Can metadata changes break a tamper-evident seal?
It depends on what byte ranges the signature covers. In PAdES, the signature typically covers the entire document. Changes to signed byte ranges invalidate it, while appending a new incremental revision may be done without breaking the original signature.
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