Hi Pilou,

normally one has to pay fees for Bitcoin transactions... BUT in this
case the free time stamping service i use (see the link in my previous post)
is FREE!!! and their servers send the data into the blockchain. :-)

Ooops. forget the link...

https://www.behance.net/gallery/67543855/Bubo-Bugi

When you download the .zip archive there is the .3dm model
file included and the the signature file and the time stampfile
(.sig file and .ots file). You simply then verify with GnuPG
the signature file against the model file and can also upload
the time stamp file and the signature file, to the free time stamp
service to check the existence there.

Regards
Stefan