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Security

Andrew Young
PLUS
Andrew Young
Courses Plus Student 639 Points
Posted by Andrew Young
Andrew Young
Courses Plus Student 639 Points

How do you exchange public key securely?

Question:

  1. Can you point out which of the following method is the most secure one? If not, can you suggest a method?
  2. Is there any improvement of your selecting best method of mine? (optional)

Question details:

In nowadays we mostly use asymmetric encryption is messaging, so in order for the encryption to work, we need to exchange public key first.

So now let's support there are two characters, Alice and Bob are transporting data using the server.

First method:

So the first method we exchange the key in plain, like this:

Bob ---Bob's key---> Server ------> Alice

And vice versa. But with this method, the MITM attack can change the key in the middle of the process. So, will the issue still be able to happen if we use DV SSL?

Second method:

And the second method, we add verifications, like this:

               Server key database
                        |
                      encrypt
                        |
Bob ---Bob's key+verification ---> Server ---> Alice

But with the following design, I'm not sure if there any vulnerable?

1 Answer

Steven Parker
Steven Parker
231,275 Points
Steven Parker
Steven Parker
231,275 Points

On your first method, DV SSL is vulnerable to MITM attacks. DV SSL should not be used for financial or other high-risk data transfers.

You didn't describe what "verfication" was for the second method, but assuming you meant EV SSL, that should be adequate for sensitive data.

Andrew Young
Andrew Young
Courses Plus Student 639 Points
Andrew Young
Andrew Young
Courses Plus Student 639 Points

Sorry for that, here is more details about method 2:

                                     Server key full db
                                                    |
                                    Server key database (server key db)(store some random keys from full db)
                                                   |
Bob--connection request --> server --accept, give the url to get key db and token-->(next line)
    |----{Bob's key+[userid+token+timestamp (iso, UTC)]}  ---> server ----|
              |                                     |                                                                  |  
              |                  encrypt with Bob's private key                                    |
              Encrypt with a random chosen key in server key db                     |                                                                          
 verify verification string----decrypt-----get Bob's key<----decrypted---- tries every key with the keys the send to Bob

P.S. if the flow doesn't shows right view it here