Big time discrepancy for creating scrypt hashes

[mdbergmann]

Hello.

This is just a question.

I found that for scrypt there are big differences on the 3 CL implementations I tried:

Generating a scrypt hash with the default settings takes:

• SBCL: 0.1 seconds
• LispWorks 8: 4.6 seconds
• ABCL: 19.5 seconds

Can you tell why it is so slow on LW and ABCL? Or maybe the other way around, why is it so fast on SBCL.

[glv2]

SBCL is usually good at optimizing fixnum arithmetic functions when generating the machine code, which is what cryptographic primitives use a lot. Moreover, Scrypt uses the Salsa cipher internally, and we have an optimized version (assembly) of Salsa's core for SBCL.

[mdbergmann]

Thanks.