Does scrypt use a hash algorithm?

Question

Does the scrypt program use a hashing algorithm behind the scenes?

What's the output size of scrypt (I mean the underlying algorithm, is that 4096 bits)?

Answer 1

The output size is whatever you ask PBKDF2 for; IIRC this is limited to something on the order of 4 GB.

Answer 2

Yes, it does. In fact, it uses two. If you look at the scrypt paper, you'll see that it uses

1. SHA-256 in the PBKDF2 construction for initial key expansion and for the final output generation, and

2. the Salsa 20/8 core by D. J. Bernstein as part of the actual memory-hard mixing function SMix.

(The Salsa 20/8 core is not actually a cryptographic hash function in the same sense as, say, SHA-256, but merely a part of one, but I've included it for completeness.)