Which method will generate stronger secret?

64 character secret generated by nanoid (https://www.npmjs.com/package/nanoid) with characters: 0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_- e.g.: hNr3COb9fSz5qfZBCQx3GkpLVW-tbVM0E-Nl8xgcf8Js8-l6fqOIfSd6Gk-T_nkE

or crypto.randomBytes(32).toString('hex') e.g.: d152189824ea6b25c34048960dfa57722d547eff9e4e98a67064d910010e6747

both create 64 character number but I'm not sure which is stronger as a secret for JWT signing (HS256)

  • 1
    $\begingroup$ Nanoid doesn't seem to be made for this - it generates an ID not a key. Just generating 32 secure random bytes is fine for HMAC/SHA-256 - presuming you are OK with keeping it in software of course, but that's generally OK for tokens. Don't confuse hex / base 64 with the bytes that are encoded using them. $\endgroup$
    – Maarten Bodewes
    Commented Aug 6, 2023 at 19:44
  • $\begingroup$ @MaartenBodewes do I understand correctly that decoded secret from .randomBytes() has higher entropy than secret generated from 64 alphabet characters? (e.g. decoded secret: �txK�:O�>�o/2�L�Q�B� has characters like ">" "/" and some that aren't represented in utf-8 e.g. �) so its harder to theoretically brute force it? $\endgroup$
    – wefad12292
    Commented Aug 6, 2023 at 20:06
  • $\begingroup$ That depends what is encoded by those characters. Nanoid seems to encode 126 bits of random bits from the same crypto module. For HMAC/SHA-256 you'd normally use a 256 bit / 32 byte key, and larger key sizes are unnecessary. crypto.randomBytes should normally use the RNG of the OS which is fine. Not sure about the exact entropy in there, but on a correctly configured system I'd expect 128 bits minimum. Entropy is always a bit of a laden term when it comes to PRNG's and - sorry - JavaScript / NodeJS documentations is terrible so you'd have to look into the source code to be sure. $\endgroup$
    – Maarten Bodewes
    Commented Aug 6, 2023 at 20:20
  • $\begingroup$ @MaartenBodewes got it, thanks a lot. $\endgroup$
    – wefad12292
    Commented Aug 6, 2023 at 20:44


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