Asymmetric encryption schemes do leak something about the encrypted plaintext: the length of the plaintext. How can this be mitigated?

My solution: Padding the plaintext with some string of the arbitrary length – add 1 and then a string of zeros

What are some other ways this information leak can be mitigated?

  • $\begingroup$ compression of plaintext? $\endgroup$ – Richie Frame Feb 5 '19 at 1:48
  • 3
    $\begingroup$ Some information is always leaked. Take a ciphertext of X bytes, then the plaintext is not an uncompressible byte array of a larger size. Q.E.D. If you have generic RSA encryption then the ciphertext size doesn't show any info on the size of the plaintext other than that the plaintext is ciphertext - minimum padding overhead - or smaller. Unless side channels leak this info of course. $\endgroup$ – Maarten Bodewes Feb 5 '19 at 2:25
  • $\begingroup$ Does having the RSA message be a key to encrypt the real payload work for you? $\endgroup$ – forest Feb 6 '19 at 4:18

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