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Note: This question looks like my other question — Any algorithm with a master key for decrypting private key encrypted messages? — which is perfectly answered by @real-or-random, but this one is different in how subkeys are generated.


Assume the following:

  1. Create a pair of master private/public key
  2. Create a private/public subkey #1 based on the master public key
  3. Create a private/public subkey #2 based on the master public key
  4. Encrypt data #1 with public subkey #1
  5. Encrypt data #2 with public subkey #2
  6. Possible to decrypt data #1 with both private subkey #1 and master private key
  7. Possible to decrypt data #2 with both private subkey #2 and master private key
  8. Impossible to decrypt data #1 with private subkey #2
  9. Impossible to decrypt data #2 with private subkey #1

Is there any algorithm out there that implements the above scenario?

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  • $\begingroup$ You can just use the scheme you are linking to? You could just double the private key value as secret input to a KDF. Then you can always keep or recalculate the keys of #1 and #2... $\endgroup$ – Maarten Bodewes Apr 10 '18 at 11:05

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