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There are two types of signatures,
Digital Signatures
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Considered a specific type of e-signature which uses certificate-based IDs to authenticate signer identity. The process binds the users signature to the document with encryption (using the user
During the signing process, the signer's private key ) which is then validate is used to bind their certificate cryptographically to the document. This can then be validated by a trusted CAs (Certificate Authorities) or TSP (Trust Service Provider). In addition, the signature generates a hash of the document which verifies the integrity of the document. Finally, in a enterprise setup, the CA or TSP also acts as a timestamp authority.
Electronic Signatures (e-signatures)
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Uses electronic authenticator methods to verify signer identity (email, corporate IDs ect...) to authenticate the signer's identity and then signs the document (various ways like services with Adobe). The better solutions demonstrate proof of signing using a secure process that includes an audit trail along with the final document.
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Discusses core concepts and capabilities - https://acrobat.adobe.com/ca/en/sign/capabilities/digital-signatures-faq.html
Adobe's Reference for Setting Up Digital Signatures in PDFs - https://helpx.adobe.com/ca/acrobat/using/certificate-based-signatures.html