{"id":395454,"date":"2024-06-29T12:14:05","date_gmt":"2024-06-29T12:14:05","guid":{"rendered":"http:\/\/savepearlharbor.com\/?p=395454"},"modified":"-0001-11-30T00:00:00","modified_gmt":"-0001-11-29T21:00:00","slug":"","status":"publish","type":"post","link":"https:\/\/savepearlharbor.com\/?p=395454","title":{"rendered":"How to exchange a secret key over an insecure network (EC-Diffie-Hellman algorithm)<\/span>"},"content":{"rendered":"
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Let\u2019s say you want to send an encrypted message to your friend in order to avoid it being intercepted and read by a third party. You just generate a random secret key and encrypt the message with it. Let\u2019s say you use AES<\/a>. But how do you let your friend know the key to decrypt it?<\/p>\n

You could give the key to your friend offline. Just write it on paper and give it to him\/her. But what if it\u2019s not an option?\u00a0<\/p>\n

What if you can only use an insecure<\/strong> data communication channel with a middleman intercepting the messages?<\/p>\n

\"Source:
Source: https:\/\/www.treinaweb.com.br\/blog\/termos-comuns-de-seguranca-man-in-the-middle<\/figcaption><\/figure>\n

There is a way to securely exchange secret keys even in the presence of a third party!
You just exchange some information with your friend and both of you come up with the same key<\/strong>. The middleman also sees the messages you\u2019ve exchanged. But he will never be able to guess the secret key. Does it sound exciting? Let\u2019s see how it\u2019s possible.<\/p>\n

Diffie-Hellman Algorithm<\/h4>\n

The algorithm is based on an extremely simple algebraic feature that we are all familiar with.
The commutative property of multiplication<\/strong>. In other words:<\/p>\n

A * B * C = B * A * C = C * A * B,\u00a0\u2026<\/p>\n

I know, it doesn\u2019t yet seem relevant to anything yet.<\/p>\n

A very rough (and incomplete) example<\/h3>\n