I'm trying to understand encryption a little more and couldn't get past this one nagging question. Let's just say I happen to want to send a one bit message to someone over an encrypted channel. I do the whole public key private key thing and an encrypted version comes out. How much information comes out?

Would there be any discernible pattern that someone snooping on the conversation could spot, especially if a similar message is sent with just the opposite bit over the same channel?

I couldn't think of any good reason to encrypt a one bit message since it's so ambiguous. A sequence would make more sense to encrypt to me. But if there is one.. or a few, I wouldn't mind to know why and why someone couldn't use it to reverse engineer the secret key.

I guess, a more general question would be, how safe is encryption when you know some information about the different types of things that could/will be sent? Not only content but something like the size from Server A is 15mb and so always know it'll be somewhere between such and such size when encrypted?


1 Answer 1


There are actually two parts to this question. First, the minimum size of the encrypted message will be much larger than a single bit. This is done to prevent the scenario you describe. See this question for details.

Second, here's an explanation of why decryption (or determining the private key) won't be any easier, even if you know the public key, the message, and the encrypted version of the message.

  • You should include padding else someone else could encrypt every possible 1-bit message and compare the result.
    – H. Idden
    Jan 17, 2016 at 21:37
  • @H.Idden Padding with what? Random padding?
    – curiousguy
    Dec 12, 2019 at 0:47
  • @curiousguy en.wikipedia.org/wiki/…
    – H. Idden
    Dec 19, 2019 at 21:21

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