Yes, but no such tool exists (yet) as far as I’m aware. You also need to tie the chunks together so that they cannot be rearranged, duplicated, or deleted. You

Yes, but no such tool exists (yet) as far as I’m aware. You also need to tie the chunks together so that they cannot be rearranged, duplicated, or deleted. You also need to be careful about what you think this tells you. For example, suppose you ran a competition where the winner is the first person to upload an encrypted+signed correct answer to a shared folder. An attacker can wait for somebody to upload the winning answer and then simply strip the real winner’s signature off and sign the encrypted blob (which they can’t decrypt) with their own private key - hurray, the attacker has now won the prize! If you reverse the order of signing and encryption you can run into bugs like [1]. You can securely combine public key encryption and signatures by including extra metadata fields inside each layer. Or you can use a function that provides public key authenticated encryption like NaCl’s crypto_box or the mode I’ve proposed for JOSE [2]. [1]: https://groups.google.com/forum/m/#!msg/sci.crypt/73yb5a9pz2Y/LNgRO7IYXOwJ https://groups.google.com/forum/m/#!msg/sci.crypt/73yb5a9pz2... [2]: https://tools.ietf.org/html/draft-madden-jose-ecdh-1pu-02 https://tools.ietf.org/html/draft-madden-jose-ecdh-1pu-02 Edit: clarify ambiguous use of “their”