Hi guys. Am Freitag, den 02.11.2018, 12:53 +0100 schrieb Stefan Claas: > On Fri, 2 Nov 2018 12:20:43 +0100, Wiktor Kwapisiewicz wrote: > > On 02.11.2018 10:53, Stefan Claas wrote: > > > Simply one can use a time stamping service, based on blockchain > > > technology. I can then time stamp the .pdf. and put also a > > > statement in the .pdf that the file is timestamped and don't must > > > worry in the future if one MITM would try (and why?) to alter my > > > documents. > > > > PDFs can be also timestamped when signing with standard RFC 3161 > > [0] > > timestamping service. > > > > Here's one example: > > > > https://support.globalsign.com/customer/en/portal/articles/2361790-add-timestamp-server---adobe-acrobat > > > > But there are numerous free RFC 3161 timestamping services. > > > > Of course that's not the same as blockchain, but it's already > > supported by numerous tools (like Adobe Acrobat). > > [0]: https://tools.ietf.org/html/rfc3161 > > Hi Wiktor, > > thanks a lot! Now this is awesome... i just timestamped my already > signed .pdf with Adobe Reader DC and this does not invalidate my > qualified signature, when saving the document again! :-) I must admit > i did not know this.
freetsa offers a free timestamping service based on blockchain technology, AFAIK. I use it myself to stamp PDFs. The free service offers 10 timestamps per day what should be enough for normal usage. Regards, Dirk -- Dirk Gottschalk Paulusstrasse 6-8 52064 Aachen, Germany GPG: DDCB AF8E 0132 AA54 20AB B864 4081 0B18 1ED8 E838 Keybase.io: https://keybase.io/dgottschalk GitHub: https://github.com/Dirk1980ac
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