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Diffie-Hellman Key Exchange | Computer Security

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In the previous sections, we discussed symmetric-key schemes such as block ciphers and MACs. For these schemes to work, we assumed that Alice and Bob both share a secret key that no one else knows. But how would they be able to exchange a secret key if they can only communicate through an insecure channel? It turns out there is a clever way to do it, first discovered by Whit Diffie and Martin Hellman in the 1970s. The goal of Diffie-Hellman is usually to create an ephemeral key. An ephemeral key is used for some series of encryptions and decryptions and is discarded once it is no longer needed. Thus Diffie-Hellman is effectively a way for two parties to agree on a random value in the face of an eavesdropper. A useful analogy to gain some intuition about Diffie-Hellman key exchange is to think about colors. Alice and Bob want to both share a secret color of paint, but Eve can see any paint being exchanged between Alice and Bob. It doesn’t matter what the secret color is, as long as only

Diffie-Hellman Key Exchange | Computer Security Skip to main content Menu Expand (external link) Document Search Copy Copied Computer Security 10. Diffie-Hellman key exchange In the previous sections, we discussed symmetric-key schemes such as block ciphers and MACs. For these schemes to work, we assumed that Alice and Bob both share a secret key that no one else knows. But how would they be able to exchange a secret key if they can only communicate through an insecure channel? It turns out there is a clever way to do it, first discovered by Whit Diffie and Martin Hellman in the 1970s. The goa

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