I am not getting whole idea behind Public Key Encryption technique.

As according to fact, public key encryption method uses two keys a public key known to everyone private key known only to recipient of the message

For an instance let assume, John wants to send a secure message to Jane, He uses Jane's public key to encrypt the message. Jane then uses her private key to decrypt it.

The thing i am not getting is, as far as i know if we want to encrypt any message using a key, from that same key only we can decrypt that particular message.

But in public key encryption case both keys are different than how it is possible to decrypt the message.

Please clarify my issue and guide me through if i am going anywhere wrong in understanding the whole concept


Here is a great video which shows principles for public key cryptography using colors, which makes it easy to understand for everyone: https://www.youtube.com/watch?v=YEBfamv-_do

Now what you missed is that it is possible to generate a secret key, and give away something which enables encryption but not decryption. This is the principle of public key encryption.

  • $\begingroup$ That video helped a lot. $\endgroup$ – foxt7ot Jan 7 '15 at 16:26
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    $\begingroup$ That video explains key exchange with Diffie-Hellman, not asymetric encryption. It has nothing to do with the question. Don't know why the question asker did mark this as right answer, maybe the question was something else than the written one. $\endgroup$ – Nova Jan 7 '15 at 16:42
  • $\begingroup$ It shows and intuition for key exchange. The question asker had trouble seeing how it could be that a key could be used to encrypt and not to decrypt, and the key exchange gives such intuition. You could see basic public key encryption such as ElGamal as a One-time-pad using Diffie-Hellman key exchange to share a secret between the secret key owner and the one that encrypts the message. $\endgroup$ – Florian Bourse Jan 7 '15 at 17:04

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