Node.js – diffieHellman.getPrime() Method

diffieHellman.getPrime() returns the Diffie-Hellman generated prime with the specified encoding. It returns a string in case the encoding is passed, else a buffer will be returned.

Syntax

diffieHellman.getPrime([encoding])

Parameters

It takes only one parameter

• encoding – This parameter specifies the encoding of the return value.

Example 1

Create a file with the name "prime.js" and copy the following code snippet. After creating the file, use the command "node prime.js" to run this code.

// diffieHellman.getPrime() Demo Example

// Importing cryptoDiffieHellman from the crypto module
const { createDiffieHellman } = require('crypto');

// Initializing the diffieHellman
const dh = createDiffieHellman(512);

// Generating prime from diffieHellman
let dhPrime = dh.getPrime()
console.log('Buffer (when encoding is not specified): ', dhPrime)

// Generating prime with specified encoding
dhPrime = dh.getPrime('base64')
console.log('String (when encoding is specified): ', dhPrime)

Output

Buffer (when encoding is not specified): <Buffer bd b7 17 22 2f 08 fa 82 2e b6 7d 5c 7d 25 5c 3e 17 9f 47 59 8d 67 eb 87 42 9d 86 c2 a7 85 3b 77 90 f2 e0 b9 70 8a b5 d6 9e 47 13 4c 7b ef 3e df 71 a9 ... >
String (when encoding is specified): vbcXIi8I+oIutn1cfSVcPhefR1mNZ+uHQp2GwqeFO3eQ8uC5cIq11p5HE0x77z7fcanQvU7p58u1yKv9fa3Muw==

Example 2

Let’s take a look at one more example.

// diffieHellman.getPrime() Demo Example

// Importing cryptoDiffieHellman from the crypto module
const { createDiffieHellman } = require('crypto');

// Generating keys for 'a'
const a = createDiffieHellman(512);

// Generating prime for 'a'
const primeA = a.getPrime();

// Generating a's generator
const generatorA = a.getGenerator()

// Generating a's generatorKeys
const keyA = a.generateKeys();

// Generating keys for b
const b = createDiffieHellman( primeA, generatorA );

// Generating prime for b
const primeB = b.getPrime();

// Generating b's generator
const generatorB = b.getGenerator()

// Generating b's generatorKeys
const keyB = b.generateKeys();

// Exchanging the secret
const secretA = a.computeSecret(keyB);
const secretB = b.computeSecret(keyA);

let isSymmetric =
   secretA.toString('hex') == secretB.toString('hex')

console.log( `Are keys Symmetric : ${ isSymmetric }` )
console.log("Symmetric keyA: ", secretA)
console.log("Symmetric keyB: ", secretB)

Output

Are keys Symmetric : true
Symmetric keyA: <Buffer 6a ba e7 5c b2 7a d2 b3 eb 67 ad 6e 2d 35 04 e4 cc fc a8 25 4e 03 f9 68 98 dd f6 83 53 75 5b f6 6b b3 2f 2f 09 a3 24 96 83 45 57 d5 3f 8c b2 60 ba 18 ... >
Symmetric keyB: <Buffer 6a ba e7 5c b2 7a d2 b3 eb 67 ad 6e 2d 35 04 e4 cc fc a8 25 4e 03 f9 68 98 dd f6 83 53 75 5b f6 6b b3 2f 2f 09 a3 24 96 83 45 57 d5 3f 8c b2 60 ba 18 ... >

Mayank Agarwal

Updated on: 29-Oct-2021

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