eighty-twenty

As I just wrote, I’ve ported libraries for cryptography (js-nacl) and password-based key derivation (js-scrypt) to Javascript.

Some browsers are faster at running these cryptographic routines than others. The results below are from casual (nay, unscientific!) speed measurements in the browsers I had handy on my machine.

The setup:

• Chrome 26.0.1410.43
• Safari 5.1.8 (6534.58.2)
• Aurora 21.0a2 (2013-03-30)
• Firefox 19.0.2
• Macbook Air late 2010 (3,1), 1.6 GHz Core 2 Duo, 4 GB RAM, OS X 10.6.8

I had to exclude Firefox from the nacl tests, since it lacks window.crypto.getRandomValues.

Hashing strings/bytes with SHA-512

Here we see Safari has the edge. Aurora is oddly slow.

Computing random nonces

This is a thin wrapper over window.crypto.getRandomValues. Safari wins hands-down here. I wonder how good the generated randomness is?

Authenticated encryption using a shared key

These are Salsa20/Poly1305 authenticated encryptions using a precomputed shared key. Broadly speaking, boxing was quicker than unboxing. The browsers perform roughly equally here.

Computing a shared key from public/private keys

These are operations whose runtime is dominated by the computation of a Curve25519 operation. In three of the four cases, the operation is used to compute a Diffie-Hellman shared key from a public key and a secret key; in the remaining case (crypto_box_keypair_from_seed) it is used to compute a public key from a secret key. Chrome is significantly faster than the other browsers here.

scrypt Key Derivation Function

Here, Safari is the only browser that underperforms significantly. The other three all compute an scrypt-derived key in 2–4 seconds, using defaults suggested by the scrypt paper as being suitable for interactive login.

Conclusions

scrypt is slow. Precompute Diffie-Hellman shared keys where you can.