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package cryptfs
import (
"os"
"math"
"fmt"
"golang.org/x/crypto/scrypt"
)
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.Printf("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)
}
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