package cryptfs import ( "fmt" "golang.org/x/crypto/scrypt" "math" "os" ) const ( // 1 << 16 uses 64MB of memory, // takes 4 seconds on my Atom Z3735F netbook SCRYPT_DEFAULT_LOGN = 16 ) type scryptKdf struct { Salt []byte N int R int P int KeyLen int } func NewScryptKdf(logN int) scryptKdf { var s scryptKdf s.Salt = RandBytes(KEY_LEN) if logN <= 0 { s.N = 1 << SCRYPT_DEFAULT_LOGN } else { if logN < 10 { fmt.Println("Error: scryptn below 10 is too low to make sense. Aborting.") os.Exit(1) } s.N = 1 << uint32(logN) } s.R = 8 // Always 8 s.P = 1 // Always 1 s.KeyLen = KEY_LEN return s } func (s *scryptKdf) DeriveKey(pw string) []byte { k, err := scrypt.Key([]byte(pw), s.Salt, s.N, s.R, s.P, s.KeyLen) if err != nil { panic(fmt.Sprintf("DeriveKey failed: %s", err.Error())) } return k } // LogN - N is saved as 2^LogN, but LogN is much easier to work with. // This function gives you LogN = Log2(N). func (s *scryptKdf) LogN() int { return int(math.Log2(float64(s.N)) + 0.5) }