Scrypt

scrypt is a password-based key derivation function created by Colin Percival, originally for the Tarsnap online backup service. The algorithm was specifically designed to make it costly to perform large-scale custom hardware attacks by requiring large amounts of memory.

📑 Define scrypt parameters

scrypt accepts 4 parameters: the work factor which defines the CPU/memory cost, the resources which fine-tunes sequential memory read size and performance, the parallelisation level and the desired key length.

Name	Default value	Properties	Description
Work factor (N)	32768	hash.scrypt.workfactor	Defines the CPU/memory cost. Must be a power of 2.
Resources (r)	8	hash.scrypt.resources	Defines the size of memory blocks.
Parallelisation (p)	1	hash.scrypt.parallelization	Defines the cost of parallelisation for an attacker.
Output length	64	hash.scrypt.derivedKeyLength	Defines the desired length of the final derived key

You can define a singleton custom scrypt function by calling ScryptFunction.getInstance(int, int, int, int) or ScryptFunction.getInstance(int, int, int)

SCryptFunction scrypt = SCryptFunction.getInstance(16384, 8, 2, 128);

In this case you have created a singleton instance which uses a work factor of 2¹⁴, with 8 bytes memory blocks, a parallelisation cost of 2 and that produces a 128 bytes derived key.

Alternatively if you have defined the parameters in the psw4j.properties file

SCryptFunction scrypt = AlgorithmFinder.getSCryptInstance();