From 6f9e90c414c165ff76cd7546b9898b51660a2440 Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher
Date: Sun, 13 Sep 2015 21:47:18 +0200
Subject: Encrypt key with scrypt-hashed password

---
 cryptfs/kdf.go | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 cryptfs/kdf.go

(limited to 'cryptfs/kdf.go')

diff --git a/cryptfs/kdf.go b/cryptfs/kdf.go
new file mode 100644
index 0000000..275c72e
--- /dev/null
+++ b/cryptfs/kdf.go
@@ -0,0 +1,38 @@
+package cryptfs
+
+import (
+	"fmt"
+	"golang.org/x/crypto/scrypt"
+)
+
+const (
+	// 1 << 16 uses 64MB of memory,
+	// takes 4 seconds on my Atom Z3735F netbook
+	SCRYPT_DEFAULT_N = 1 << 16
+)
+
+type scryptKdf struct {
+	Salt []byte
+	N int
+	R int
+	P int
+	KeyLen int
+}
+
+func NewScryptKdf() scryptKdf {
+	var s scryptKdf
+	s.Salt = RandBytes(KEY_LEN)
+	s.N = SCRYPT_DEFAULT_N
+	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
+}
-- 
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