Case 3 is indeed a non trivial one. 1/ put all those important to-be-published-later data in an archive 2/ obtain the archive SHA512 hash 3/ cypher the archi

Case 3 is indeed a non trivial one. 1/ put all those important to-be-published-later data in an archive 2/ obtain the archive SHA512 hash 3/ cypher the archive, using a symmetric-key algorithm and a a random key 4/ use secret sharing, with the key being the secret, with the adequate amount of redundancy (this is the most tricky part). https://en.wikipedia.org/wiki/Secret_sharing https://en.wikipedia.org/wiki/Secret_sharing 5/ give each part of the secret to some notary, and pay him to have it delivered to each member of a group of tech-savvy friends of yours. Chose unrelated notaries installed in different countries 6/ give the cyphered archive along with detailed instructions to each member of the group, in order for him to be able to rebuild the secret and then decrypt the archive. If they will have to act this way more than 10 years after receiving the instructions give them full "image systems" (a real machine!) storing all required software, ready to run 7/ publish the SHA512 hash (on archive.org?), sealed-signed by you, along with some explanation "At date X I, John Smith, created the archive whose digest is...". You may also publish the cyphered archive (this is not very useful and raises the risk) 8/ pray. The symmetrical cypher has to resist attacks during the timelapse, enough groupmembers have to survive long enough, image systems must be usable when time comes...