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I have application working between server and client. All messages must be encrypted and decrypted. I use AES algorithm and I want method to hide the key.

I found Diffie-Hellman algorithm, but my problem is that I didn't find its source code. If the is another method for key exchange, please tell me.

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    three letters: TLS – SEJPM Dec 27 '15 at 20:57
  • Is there a reason why you are looking to implement this on your own versus using an existing solution? – Neil Smithline Dec 28 '15 at 0:13
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This is exactly what SSL/TLS are supposed to do. SSL/TLS uses asymmetric encryption just in the handshake to exchange the symmetric key that is used from that moment on to encrypt the communication. The key exchanged is called a masterkey and is only used for that session. The lifetime of a session can be configured.

The process is basically this when you use HTTPS, for example:

  • Client establishes connection (three-way-handshake -> TCP handshake, after this the SSL/TLS handshake starts)
  • Server sends certificate (which includes the public key)
  • Client sends masterkey encrypted with the servers public key
  • Masterkey is used for that session

This is of course just a broad description of the protocol and only applies when the client itself has no certificate which is the case in most scenarios.

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