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DynaPDF Manual - Page 55

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Digital Signatures
Page 55 of 750
What is stored in a signature field?
When signing a PDF file with the internal signature handler, DynaPDF creates a signature
object that contains the file’s signature and a PKCS#1 certificate that was extracted from the
PKCS#12 certificate. The difference between both certificate types is that a PKCS#1 certificate
contains no private key.
A viewer application validates the signature by using the public key that is stored in the
PKCS#1 certificate object. Because the private key is not stored in the PDF file it is impossible to
sign other PDF files with the certificate that can be extracted from the PDF file.
When signing the file with an external signature handler a PKCS#7 signature object will be
stored in the PDF file. This is just another signature format that contains of course no private
key too.
How to validate a signature?
Acrobat validates signatures from unknown certificates not automatically. The certificate must
first be added to the list of trusted identities. Once a certificate was added to the list of trusted
identities, signatures of other documents which use the same certificate will be automatically
validated.
 

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