Well the use of digital certificats for timestamping is explicitely covered in Directive 1999&#x2F;93&#x2F;EC [1]. I&#x27;ll freely admit not being up to date on the situation on the other side of the Atlantic. While Bitcoins may start to get some recognition as an asset, I&#x27;d wage real money that no law anywhere explicitely recognize the blockchain as a legaly opposable timestamping authority.<p>And your stated used case <i>&quot;Local archives are useful for personal purposes, but sometimes, in investigations that may be controversial, you want to be able to prove that the copy you downloaded was not modified and you need to timestamp it&quot;</i> looks like planning to defend yourself in court to me...<p>[1] <a href="http:&#x2F;&#x2F;eur-lex.europa.eu&#x2F;legal-content&#x2F;EN&#x2F;TXT&#x2F;?uri=celex:31999L0093" rel="nofollow">http:&#x2F;&#x2F;eur-lex.europa.eu&#x2F;legal-content&#x2F;EN&#x2F;TXT&#x2F;?uri=celex:319...</a> also <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Electronic_Signatures_Directive" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Electronic_Signatures_Directiv...</a>