How do digital signatures on PDF documents work? Ask Question. Asked 5 years, 4 months ago. Active 5 years, 4 months ago. Viewed 2k times. Improve this question. Jim 5 5 bronze badges. Minaj Minaj 1, 1 1 gold badge 13 13 silver badges 22 22 bronze badges. Were you logged into an Adobe account when you did the signature? All software that can sign PDF would necessarily have some crypto library.
What kind of information did you enter to get the signature? No I did not sign up on any account. I was sent a PDF by email, downloaded it, filled it out, went through the signing process and attached it to email and sent back to the person who sent it. Please share the PDF for analysis so we can tell what you have. You can share the PDF e. I expanded my answer, see below. Add a comment. Active Oldest Votes.
The recipient can manually establish a trust relationship with the signer's key if desired. The program calculates a new hash for the document.
If this new hash matches the decrypted hash from Step 1, the program knows the document has not been altered and displays messaging alone the lines of, "The document has not been modified since this signature was applied. The program also validates that the public key used in the signature belongs to the signer and displays the signer's name.
Now that you know how the digital signature process verifies the signer's identity and that no changes have been made, let's take a quick look at how that is communicated to people viewing the document.
You can see in the screenshots below that both digitally signed Office documents and PDFs clearly display messaging about the validity of the signature and the content. Example digital signature in Microsoft Word. CAs, a type of Trust Service Provider, are third-party organizations that have been widely accepted as reliable for ensuring key security and that can provide the necessary digital certificates.
Both the entity sending the document and the recipient signing it must agree to use a given CA. That means you can always send a document with a digital signature by using DocuSign as the Certificate Authority. Alternatively, you can securely establish your own CA using the DocuSign Signature Appliance and still access the rich features of DocuSign cloud services for transaction management.
Some organizations or regions rely on other prominent CAs, and the DocuSign platform supports them, as well. See the full list of Certificate Authorities we support. Many industries and geographical regions have established eSignature standards that are based on digital signature technology, as well as specific certified CAs, for business documents.
Following these local standards based on PKI technology and working with a trusted certificate authority can ensure the enforceability and acceptance of an e-signature solution in each local market. By using the PKI methodology, digital signatures utilize an international, well-understood, standards-based technology that also helps to prevent forgery or changes to the document after signing. Both acts made electronically signed contracts and documents legally binding, like paper-based contracts.
Since then, the legality of electronic signatures has been upheld many times. By now, most countries have adopted legislation and regulations modeled after the United States or the European Union, with a preference in many regions for the E. In addition, many companies have improved compliance with the regulations established by their industries e.
These country- and industry-specific regulations are continuously evolving, a key example being the Electronic identification and trust services eIDAS regulation that was recently adopted in the European Union. A digital certificate is an electronic document issued by a Certificate Authority CA.
It contains the public key for a digital signature and specifies the identity associated with the key, such as the name of an organization. The certificate is used to confirm that the public key belongs to the specific organization.
The CA acts as the guarantor. Digital certificates must be issued by a trusted authority and are only valid for a specified time. In order to ensure that a document has not been modified by someone other than its author, and to verify that the author is who we expect and not somebody else, digital signatures are necessary.
Imagine that somebody intercepts a PDF document with some important contractual agreement and tries to modify it to show different terms. Digital signatures in PDF documents use the concept of hashing to prevent such a scenario. A hash is a mathematical function that converts an arbitrary block of data into a fixed-size string.
The result of this hash function is always identical provided that the block of data has not been modified. However, this does not completely solve the problem of document integrity. What if a malicious person guesses the hash function that was used, modifies the PDF document, and then stores the new hash in it?
To solve this second problem, we need asymmetric encryption. But this requires that both parties are able to securely and secretly communicate the encryption key they are going to use beforehand.
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