Diffie–Hellman key exchange (Diffie–Hellman) algorithm principle and PHP implementation version_PHP tutorial

Diffie-Hellman key exchange (Diffie-Hellman) algorithm principle and PHP implementation version

This article mainly introduces the Diffie-Hellman key exchange (Diffie–Hellman) algorithm principle and PHP implementation version, friends in need can refer to it

Diffie-Hellman is an algorithm that allows both parties to establish a secret key on an insecure public channel. Both parties can later use this secret key to encrypt content (such as RC4).

The principle of Diffie–Hellman algorithm is very simple:

Based on the above principle, it is easy to prove through mathematical principles that (g^b%p)^a%p = (g^a%p)^b%p, so they get the same key.

Except for a, b and the final public key, which are secret, the others can be transmitted on the public channel. In practical applications, p is very large (more than 300 bits), and g usually takes 2 or 5. Then it is almost impossible to calculate a from p, g and g^a%p (discrete math problem).

Many languages ​​have implemented this algorithm. Take Crypt_DiffieHellman in the PHP package as an example:

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