Does crypto block the Node.js event loop?

[lffg]

• Node.js Version: 10.x
• OS: OS X
• Scope (install, code, runtime, meta, other?): Runtime
• Module (and version) (if relevant): crypto

I recently found out that the crypto Node.js module is not asynchronous.

In my application, I am validating a JWT token on every request, so should I worry about the fact that this module is synchronous? My biggest concern is that this module could block the event loop.

Thanks in advance. :)

[addaleax]

Most crypto work is synchronous, but there are a few exceptions (e.g. random bytes generation, key pair generation, PBKDF2/scrypt).

For a lot of operations, and in particular hashes, I would expect the overhead of moving tasks to a threadpool to outweigh the cost of a synchronous call.

There are some cases where this is a known issue though, see e.g. nodejs/node#28404.

[gireeshpunathil]

ping @lffg - is there anything outstanding here, to be clarified?

[lffg]

No, thanks. Forgot to close. :)