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PDF signature space

Posted: 07/03/2013 02:01:09
by Kees de Wit (Standard support level)
Joined: 06/13/2013
Posts: 17

I'm signing PDF with the example project (ASPNet_Distributed) and it gives me this error out of the box: "No enough space for signature"

Setting the ExtraSpace property of the TElPDFSignature instance will solve it. My question is that I have to set it to 150000 to take away the error, but is this value within range of expectation? Is there a better way to determine the space? If in some cases we have the publickey in presign stage, does this make the space calculation somehow easier (can it be done in another way)?
Posted: 07/03/2013 02:09:02
by Vsevolod Ievgiienko (Team)

Thank you for contacting us.

Unfortunatelly there is no reliable way to get estimated signature size before the actual signing procedure is performed. Please refer to this article for details: https://www.eldos.com/security/articles/7645.php
Posted: 07/03/2013 02:19:29
by Ken Ivanov (Team)

Hello Kees,

While there are no options of predicting PAdES signature size in distributed signing mode at the moment, there is such an option in 'normal' signing mode (by setting the SignatureSizeEstimationStrategy to psesSmart or psesSmartAndTrialTimestamp). We plan to extend the distributed signing mode with support for SignatureSizeEstimationStrategy property in one of the future product updates.

The upcoming SecureBlackbox update (which will be released by the end of the week) will also contain an option of suppressing inclusion of CRL elements (which can be of fairly large and hardly predictable size) to the signature wherever there is a relevant OCSP response available. OCSP responses are shorter in size and thus it is easier to allow proper signature space for them.



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