scrypt

scrypt is a password-based key derivation function published by Colin Percival in 2009 and standardised in RFC 7914 that combines PBKDF2-HMAC-SHA-256 with a memory-hard inner mixing step called ROMix, built on the Salsa20/8 core. Its three tunable parameters are N (memory/CPU cost), r (block size) and p (parallelism); a typical interactive setting is N=2^15, r=8, p=1, requiring around 32 MiB. The memory-hard design dramatically increases the cost of GPU and ASIC attacks compared with PBKDF2 or bcrypt. scrypt remains a safe choice for password hashing and KDF, although Argon2id is generally preferred for new designs; Litecoin and Dogecoin use scrypt as their proof-of-work function.