crypto.getDiffieHellman() Method in Node.js

The crypto.createDiffieHellmanGroup() is used for creating a pre-determined DiffieHellmanGroup key exchange object. Some of the supported DiffieHellmanGroups are: modp1, modp2, modp5, modp 14, modp16, modp17 etc. The benefit of using this method is that the parties don't need to generate or exchange a group modulus thus saving processing time.

Syntax

crypto.getDiffieHelmmanGroup(groupName)

Parameters

The above parameters are described as below −

• groupName – It takes the input for the group name. The input is of type 'string'.

Example

Create a file with name – getdiffieHellman.js and copy the below code snippet. After creating file, use the following command to run this code as shown in the example below −

node getDiffieHellman.js

getdiffieHellman.js

// crypto.getDiffieHellman() Demo Example

// Importing the crypto module
const crypto = require('crypto');

const server = crypto.getDiffieHellman('modp1');
const client = crypto.getDiffieHellman('modp1');

// Printing DiffieHellman values
console.log(server);
console.log(client);

// Generating public and private keys
server.generateKeys();
client.generateKeys();

// Gettong public key
const serverSecret = server.computeSecret(client.getPublicKey(), null, 'hex');
const clientSecret = client.computeSecret(server.getPublicKey(), null, 'hex');

/* aliceSecret and bobSecret should be the same */
console.log(serverSecret === clientSecret);

Output

C:\home\node>> node getDiffieHellman.js
DiffieHellmanGroup { _handle: { verifyError: [Getter] }, verifyError: 0 }
DiffieHellmanGroup { _handle: { verifyError: [Getter] }, verifyError: 0 }
true

Example

Let's take a look at one more example.

// crypto.getDiffieHellman() Demo Example

// Importing the crypto module
const crypto = require('crypto');

const dh1 = crypto.getDiffieHellman('modp17');
const dh2 = crypto.getDiffieHellman('modp14');

// Generating public and private keys
dh1.generateKeys();
dh2.generateKeys();

// Gettong public key
const dh1Key = dh1.computeSecret(dh2.getPublicKey(), null, 'hex');
const dh2Key = dh2.computeSecret(dh1.getPublicKey(), null, 'hex');

/* aliceSecret and bobSecret should be the same */
console.log(dh1Key === dh2Key);

Output

C:\home\node>> node getDiffieHellman.js
internal/crypto/diffiehellman.js:102
const ret = this._handle.computeSecret(toBuf(key, inEnc));
                        ^
Error: Supplied key is too large
   at DiffieHellmanGroup.dhComputeSecret [as computeSecret]
(internal/crypto/diffiehellman.js:102:28)
   at Object.<anonymous> (/home/node/test/getDiffieHellman .js:15:20)
   at Module._compile (internal/modules/cjs/loader.js:778:30)
   at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
   at Module.load (internal/modules/cjs/loader.js:653:32)
   at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
   at Function.Module._load (internal/modules/cjs/loader.js:585:3)
   at Function.Module.runMain (internal/modules/cjs/loader.js:831:12)
   at startup (internal/bootstrap/node.js:283:19)
   at bootstrapNodeJSCore (internal/bootstrap/node.js:623:3)