Depending on the type of signature, electronic signatures offer a high level of protection against forgery and tampering. In the case of advanced electronic signatures (FES) and qualified electronic signatures (QES) in particular, cryptographic methods ensure that subsequent changes to the signed document can be detected.

With sproof, signature processes are also documented through a tamper-proof audit trail. This allows important information about the signature process to be recorded in a traceable and verifiable manner.

As soon as a document is digitally signed via sproof, a cryptographic hash value is applied to its content.

• Subsequent changes: If even a single character, decimal place, or image in the PDF is changed after signing, the seal is invalidated.
• Result: Any standard validation tool (e.g., Adobe Acrobat or the free sproof Validator) immediately reports that the document has been modified and that the signature is invalid.