Thank you for your patience.
After investigating the sample you provided, we found only
hash details for the signature. As a result, we were unable to determine the
actual cause of the problem you are currently facing. We kindly request you to
follow the steps below and share the result details with us:
Step 1: Create an empty signature using your public
certificate. You can refer to the example code here: [link to the example](https://github.com/SyncfusionExamples/PDF-Examples/blob/master/Digital%20Signature/Deferred-signing-in-PDF-document/.NET/Deferred-signing-in-PDF-document/Program.cs#L21).
Step 2: When creating the empty signature file, please
follow the steps outlined in the sign block. You can find the instructions
here: [link to the code](https://github.com/SyncfusionExamples/PDF-Examples/blob/master/Digital%20Signature/Deferred-signing-in-PDF-document/.NET/Deferred-signing-in-PDF-document/Program.cs#L94).
The "message" parameter represents the bytes of a
document sequence, but it should be a calculated hash or digest value.
Therefore, before externally signing the document, you need to generate a hash
or digest value from the message bytes, as indicated below:
|
public byte[] Sign(byte[] message, out byte[]
timeStampResponse)
{
byte[] digest;
using (SHA256Managed sha = new SHA256Managed())
{
digest = sha.ComputeHash(message);
}
SignDocumentHash(digest); // Convert digest bytes to
base64/Hex format if requested to send to sign the digest.
// Set a null value to create an empty
signed document.
byte[] signedBytes = null;
timeStampResponse = null;
return signedBytes;
}
|
Step 3: Please use the following overload for DeferredSign:
If your signed digest message already contains encoded PKCS7
information, use the following overload to replace your signed signature bytes:
|
// Deferred signing without PKCS7 encoding.
PdfSignature.ReplaceEmptySignature(inputFileStream,
pdfPassword, outputFileStream, signatureName, externalSigner,
publicCertificates, false);
|
Otherwise, if you need to replace your signed signature
bytes, use the following overload:
|
PdfSignature.ReplaceEmptySignature(inputFileStream,
pdfPassword, outputFileStream, signatureName, externalSigner,
publicCertificates);
|
Step 4: Replace your signed signature bytes as shown in the
code here: [link to the code](https://github.com/SyncfusionExamples/PDF-Examples/blob/master/Digital%20Signature/Deferred-signing-in-PDF-document/.NET/Deferred-signing-in-PDF-document/Program.cs#L137).
|
public byte[] Sign(byte[] message, out byte[]
timeStampResponse)
{
// Set the signed hash message to
replace an empty signature.
byte[] signedBytes = _signedHash;
timeStampResponse = null;
return signedBytes;
}
|
Please try the above-mentioned steps on your side. If the
problem persists, we kindly request you to share your signing block information
or complete code details with us for further investigation.
