at.gv.egiz.pdfas.framework.vfilter
Interface VerificationFilterParameters

All Known Implementing Classes:

VerificationFilterParametersImpl

public interface VerificationFilterParameters

The parameters of the VerificationFilter algorithm.

Author:

wprinz

Method Summary

boolean	assumeOnlySignatureUpdateBlocks() Tells the VerificationFilter to assume that there are only singatures (and their Incremental Update blocks) younger than the original document.
boolean	extractBinarySignaturesOnly() Tells the VerificationFilter to extract binary signatures only.
boolean	scanForOldSignatures() Tells the VerificationFilter so scan for old signatures in the rest text.

Method Detail

extractBinarySignaturesOnly

public boolean extractBinarySignaturesOnly()

Tells the VerificationFilter to extract binary signatures only.

Not scanning for textual signatures allows the algorithm to skip text extraction and signature extraction, which are both time and memory intensive processes.

Returns:

Returns true if the VerificationFilter should extract binary signatures only.

assumeOnlySignatureUpdateBlocks

public boolean assumeOnlySignatureUpdateBlocks()

Tells the VerificationFilter to assume that there are only singatures (and their Incremental Update blocks) younger than the original document.

This is equivalent to saying that the document was not updated using an Incremental update block other than a signature after being singed. The incremental update blocks after the original document contain only signatures (either text or binary).

This is equivalent to saying that there exists no Incremental Update block that would render a text signature before it invalid.

Under this assumption, the process of finding all text signatures simplifies to one text extraction of the whole document and one signature extraction. This is of course a massive performance gain.

Actually the algorithm performs a text extraction of the whole document not including trailing binary signature Incremental Update blocks. This means that if a the last n Incremental Update blocks of a document are binary, there is no use extract text from them.

Note that if there are Incremental Update blocks with text after a signature thus this assumption does not hold the signatures older than this block will break.

Returns:

Returns true if the Verification filter should assume that there are only signature blocks after the original document.

scanForOldSignatures

public boolean scanForOldSignatures()

Tells the VerificationFilter so scan for old signatures in the rest text.

The rest text is the text of the oldest text signature or the original document text if there is no text signature.

Returns:

Returns true if the VerificationFilter should scan for old text signatures in the rest text.