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I want to use PKI to encrypt a message. How this generally done is to PKI encrypt an AES key and then encrypt the message. The problem(in my case) with this method is that you can also ask someone to just decrypt the key.

The reason this is a problem is because I want to encrypt something and give a package to person A that then can give it to person B but person A should not learn it's content.

Now I can do a block-wise PKI encryption and each block add the hash/MAC of the previously encrypted block. The most important information would be the last block (the first block(s) contains contact information in case of malicious use of the data, I want to make sure person B gets this info, so partial decryption must be impossible)

My question is, is there already an existing scheme that supports this?

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    $\begingroup$ "The reason this is a problem is because I want to encrypt something and give a package to person A that then can give it to person B but person A should not learn it's content."; does person A have the PKI private key? If B is the only one with that key, what is the concern? $\endgroup$ – poncho Dec 11 '20 at 14:48
  • $\begingroup$ @poncho because of legal reasons a government could enforce to just decrypt the AES key so that the party holding the package (of person A) could access it without compromising the key of person B $\endgroup$ – ovanwijk Dec 11 '20 at 19:14
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    $\begingroup$ Again, you might want to clarify your assumptions; if A doesn't know the private key, then they cannot give any decrypted information (either the encrypted message or the key) to the government. If they do (and they know everything else that B needs to decrypt), then there is nothing preventing them from complying with the government's request (and playing around with chaining hash/MACs from previous blocks wouldn't help). So, what does A know (and what does B know that A doesn't)? $\endgroup$ – poncho Dec 13 '20 at 3:09

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