Using tcpdf library I'm able to add a signature to pdf but timestamp (RFC3161) is not yet implemented in this library (applyTSA) and I need this feature.
According to ISO 32000-1:2008:
Time stamp information as an unsigned attribute (PDF 1.6): The timestamp token shall conform to RFC3161 and shall be computed and embedded into the PKCS#7 object as described in Appendix A of RFC3161. The specific treatment of timestamps and their processing is left to the particular signature handlers to define.
From RFC3161 APPENDIX A
The following object identifier identifies the Signature Time-stamp attribute:
id-aa-timeStampToken OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) aa(2) 14 }
The Signature time-stamp attribute value has ASN.1 type SignatureTimeStampToken:
SignatureTimeStampToken ::= TimeStampToken
The value of messageImprint field within TimeStampToken shall be a hash of the value of signature field within SignerInfo for the signedData being time-stamped.
It is very easy to generate the timestamp using openssl but it is not clear to me how to embed it into PKCS#7 object. My questions are:
- How can I add timestamp to my signature?
- Or, there is any open source library (php or else) with this feature?
An example will be appreciated