Definition | Diffie-Hellman | Futura Tech

Key exchange Diffie-Hellman is a specific encryption method developed by Whitfield Diffie and Martin Hellman and published in 1976, one of the first implementations in the field of cryptography.

The Diffie-Hellman key exchange method allows two parties, who do not know each other a priori, to share a secret key under an unsecured communication channel. Such a key can be used to encrypt subsequent messages using a scheme of encryption with symmetric key.

This concept was originally invented by Malcolm Williamson, an employee of the Government Communications Headquarters (GCHQ) in the United Kingdom, a few years before Whitfield Diffie and Martin Hellman, but the GCHQ decided not to make this discovery public, because it was a matter of national security. This method was used for the RSA encryption, another method of cryptography at public key using algorithms asymmetrical.

 

How does the Diffie-Hellman algorithm work?

The following diagram illustrates the concept of key exchange using colors instead of a very large number. At first, a common color is shared between Marie and Antoine, which can be observed by a third party interested in the communication between the two.

The next step is for Marie and Antoine to each choose their secret color, which is not shared with anyone. Each makes a primary blend with the common color and their secret colors.

The key step in the process is that Marie and Antoine only exchange their primary mixes. These primary mixtures, the result of combinations of the common color and the secret colors, can hardly be reversed and determine which secret colors Marie and Antoine used if a third party listens to the communication.

Marie and Antoine then use their secret colors on the primary mixtures they have received, generating secondary mixtures (common key) which will be the same for Marie and Antoine, without a third party observing the communication being able to produce this secondary mixture. Marie and Antoine use their common key to encrypt and decrypt their messages secretly.

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