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Multiple diffieHellman.generateKeys calls don't update the public key #56990
Description
Affected URL(s)
https://nodejs.org/docs/latest-v22.x/api/crypto.html#diffiehellmangeneratekeysencoding
Description of the problem
The documentation regarding diffieHellman.generateKeys([encoding]) in crypto module states as follows:
This function is a thin wrapper around DH_generate_key(). In particular, once a private key has been generated or set, calling this function only updates the public key but does not generate a new private key.
I have not been able to observe in any way that calling generateKeys multiple times results in different public keys.
import { createDiffieHellman } from 'node:crypto'
const alice = createDiffieHellman(1024)
const public1 = alice.generateKeys('hex')
const public2 = alice.generateKeys('hex')
const public3 = alice.generateKeys('hex')
console.log(public1 === public2) // true
console.log(public1 === public3) // true
console.log(public2 === public3) // trueNodeJS docs state that it is a thin wrapper around OpenSSL's DH_generate_key. The OpenSSL page on DH_generate_key states that as follows in their docs:
All of the functions described on this page are deprecated. Applications should instead use EVP_PKEY_derive_init(3) and EVP_PKEY_derive(3).
Is it possible this is the result of such deprecation?
Activity
bnoordhuis commentedon Feb 11, 2025
Not a bug but maybe a case of unclear documentation. See commit 4a82c8f for why that paragraph was added.
Public key generation is a deterministic process. You don't change any parameters so of course the public key stays the same. If you called
dh.setPublicKey(some_other_pubkey)and then call generateKeys again, you get the old public key again.doc: clarify diffieHellman.generateKeys recomputes same key
github-actions commentedon Apr 21, 2026
This issue has been marked as stale due to 210 days of inactivity.
It will be automatically closed in 30 days if no further activity occurs. If this is still relevant, please leave a comment or update it to keep it open.
doc: clarify diffieHellman.generateKeys recomputes same key
doc: clarify diffieHellman.generateKeys recomputes same key
doc: clarify diffieHellman.generateKeys recomputes same key
doc: clarify diffieHellman.generateKeys recomputes same key