crypto_scrypt(passwd, passwdlen, salt, saltlen, N, r, p, buf, buflen): Compute scrypt(passwd[0 .. passwdlen - 1], salt[0 .. saltlen - 1], N, r, p, buflen) and write the result into buf. The parameters r, p, and buflen must satisfy r * p < 2^30 and buflen <= (2^32 - 1) * 32. The parameter N must be a power of 2 greater than 1.