Settings and activity
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5 votes
mkl
supported this idea
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1 vote
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1 vote
An error occurred while saving the comment mkl
commented
> One of the main reason why do I prefer the author signature (means the certificate) is as this allows an additional information within the signature (like company logo, the individual reason for approval, Acrobat version etc.).
These features also work for approval signatures.
Both author signatures (aka "certification signatures") and approval signatures in PDFs use X.509 certificates and digital signatures (to cryptographically secure the document with a connection to an identifiable person) and allow a visualization of the signature containing arbitrary information.
(Adobe really made things difficult by calling one of these two signature types "certification"...)
The difference is how the signature is displayed. Furthermore, up to the old ISO 32000-1 standard only the author signature could restrict which changes in general are allowed to the signed document. Nowadays, though, approval signatures can (further) restrict this.
An error occurred while saving the comment mkl
commented
> Honestly, I do not understand the difference between "Digitally sign" and "Certify"
Technically they are very similar. "Certify" actually is a special case of a digital signatures that is reserved for the first signer of a document, also called "author signature". Thereafter a document can still be "Digitally signed" many times if the author originally allowed this. This signatures also are known as "approval signatures".
Whether you as initial signer create an author signature or an approval signature, is not relevant. The other signers must not use author signatures, though, they must use approval signatures.
> Another concern is that each signer can remove his certificate afterwards which is not optimal.
It's a choice of Adobe that each signer can remove their signature from a document. This strictly speaking is not according to the PDF specification.
An error occurred while saving the comment mkl
commented
I'm not sure we correctly understand each other.
In the "Use a certificate" menu I see the options "Digitally sign", "Timestamp", "Validate all signature(s)", "Certify (visible signatures)", and "Certify (invisible signatures)".
When I asked "Have you tried using it to digitally sign instead?" I meant using the "Digitally sign" option there. That option also uses your personal, local certificate, it does not "require E-signatures through an Adobe Sign" as you say.
Thus, have you or the other prospective signers tried to use that option?
An error occurred while saving the comment mkl
commented
>Unfortunately, the option 2) and 3) do not work properly, so when sending the PDF file that contains my digital signature and asking others to sign this document with their own certificates, the users are not able to proceed.
What do you mean by "the users are not able to proceed"? What exactly have they tried and how did it fail?
That being asked, have you prepared empty signature fields for those other users to use for signing?
Also you use your certificate to certify the document. Have you tried using it to digitally sign instead?
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1 vote
An error occurred while saving the comment mkl
commented
Redaction is one of the most intense editing actions to a PDF. If you allow redaction, you don't need security at all anymore.
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3 votesmkl
supported this idea
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An error occurred while saving the comment mkl
commented
As far as I can tell, your time stamp is ok.
After cutting off your DTS revision, online Acrobat started recognizing the other signatures but failed to trust your AATL certificates.
Apparently the validation related code in the current online Acrobat is broken.
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1 vote
An error occurred while saving the comment mkl
commented
I just had a look at Case1.pdf. Together with the third signature a number of (unnecessary!) changes were applied to page dimensions and page resources. This breaks earlier signatures.
Case2.pdf ... Case5.pdf are different, here there are errors in the internal PDF structure of the respective first revisions. When loading the documents, Acrobat repairs this which breaks signatures. -
1 vote
An error occurred while saving the comment mkl
commented
Any program that can read a PDF obviously can manipulate it in any way it likes. Thus, this is nothing Adobe can do anything about.
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10 votes
An error occurred while saving the comment mkl
commented
Your documents have the NeedAppearances flag set to true. This makes any signatures therein questionable as it instructs any PDF processor to "construct appearance streams and appearance dictionaries for all widget annotations in the document". Thus, chances are that the signer saw something different when signing than another person viewing the signed document, in particular if a different viewer program is used.
If you set that flag to false (or don't add it at all), Adobe Acrobat recognized the signature.
Please share example documents illustrating the issue.