shamir secret sharing & GnuPG to share secrets among parties (majority needed to decrypt).
example: sensitive material is collected on a server and needs to be shared with an outside party that only has access if a majority of the personell allowed to view such material agrees to see it.
example: you want to send your diary or a secret message to all of your friends in case you die (ZOMG), but no single person alone should be able to read it. You select a group of friends (e.g. five) and send them your secret, if more than half of them agree to decrypt they are able to read it.
Your friends will recieve a symmetrically encrypted message wrapped in a GPG mail and part of the key that decrypts this message. Hence only the specified recipient can view their share of the key that decrypts the message. Everyone gets the same encrypted message (ciphertext) within the GPG mail. This trivial script builds upon secretshare and GnuPG and can be used to retrieve the key collectively which then can be used to decrypt your shared, secret message with GnuPG. It's available as a git submodule in this repo. Just initialize and update. You'll need rust to compile.
Keep in mind that it's very improbable that this method will be useful with recipients unfamiliar with the technology used here.
NO WARRANTY WHATSOEVER!
..It's also unlikely that this project will be maintained much. It's a (very) quick hack that didn't fit on a GitHub gist.
pipe any file or message to stdin and specify the recipients as arguments:
echo "share a secret among my friends" | ./share peter@noname.cc \
robin@noname.cc justin@noname.cc jaqueline@noname.cc"
./share a@example.org b@example.org c@example.org <<<JFKs_true_assasin.txt
CC0 1.0 Public Domain Dedication: https://creativecommons.org/publicdomain/zero/1.0/