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authorJakob Unterwurzacher2023-01-08 22:15:39 +0100
committerJakob Unterwurzacher2023-01-08 22:17:14 +0100
commit88bc0aa60748405db94410c8f149e62683638f80 (patch)
tree301d532efd8962f895d1d60a09d550cfd8d4a952
parent0b5b864a067a530ed00f01baf12ad4de5bb60e27 (diff)
MANPAGE: scryptn: list how much memory is needed
Calculated acc. to https://words.filippo.io/the-scrypt-parameters/ , and add benchmarks to double-check the numbers. They match.
-rw-r--r--Documentation/MANPAGE.md33
-rw-r--r--internal/configfile/scrypt_test.go75
2 files changed, 61 insertions, 47 deletions
diff --git a/Documentation/MANPAGE.md b/Documentation/MANPAGE.md
index 45c60c6..47092cf 100644
--- a/Documentation/MANPAGE.md
+++ b/Documentation/MANPAGE.md
@@ -563,15 +563,44 @@ Quiet - silence informational messages.
Applies to: all actions.
#### -scryptn int
-scrypt cost parameter expressed as scryptn=log2(N). Possible values are
-10 to 28, representing N=2^10 to N=2^28.
+gocryptfs uses *scrypt* for hashing the password when mounting,
+which protects from brute-force attacks.
+
+`-scryptn` controls the *scrypt* cost parameter "N" expressed as scryptn=log2(N).
+Possible values are `-scryptn=10` to `-scryptn=28`, representing N=2^10 to N=2^28.
Setting this to a lower
value speeds up mounting and reduces its memory needs, but makes
the password susceptible to brute-force attacks. The default is 16.
+The memory usage for *scrypt* during mounting is as follows:
+
+ scryptn Memory Usage
+ ======= ============
+ 10 1 MiB
+ 11 2
+ 12 4
+ 13 8
+ 14 16
+ 15 32
+ 16 64
+ 17 128
+ 18 256
+ 19 512
+ 20 1 GiB
+ 21 2
+ 22 4
+ 23 8
+ 24 16
+ 25 32
+ 26 64
+ 27 128
+ 28 256
+
Applies to: `-init`, `-passwd`
+See also: the benchmarks in the gocryptfs source code in internal/configfile.
+
#### -trace string
Write execution trace to file. View the trace using "go tool trace FILE".
diff --git a/internal/configfile/scrypt_test.go b/internal/configfile/scrypt_test.go
index 30f37a1..1c90c0a 100644
--- a/internal/configfile/scrypt_test.go
+++ b/internal/configfile/scrypt_test.go
@@ -1,60 +1,45 @@
package configfile
import (
+ "fmt"
"testing"
)
/*
-Results on a 2.7GHz Pentium G630:
-
-gocryptfs/cryptfs$ go test -bench=.
+$ time go test -bench . -run none
+goos: linux
+goarch: amd64
+pkg: github.com/rfjakob/gocryptfs/v2/internal/configfile
+cpu: Intel(R) Core(TM) i5-3470 CPU @ 3.20GHz
+BenchmarkScryptN/10-4 339 3488649 ns/op 1053167 B/op 22 allocs/op ... 3ms+1MiB
+BenchmarkScryptN/11-4 175 6816072 ns/op 2101742 B/op 22 allocs/op
+BenchmarkScryptN/12-4 87 13659346 ns/op 4198898 B/op 22 allocs/op
+BenchmarkScryptN/13-4 43 27443071 ns/op 8393209 B/op 22 allocs/op
+BenchmarkScryptN/14-4 21 56931664 ns/op 16781820 B/op 22 allocs/op
+BenchmarkScryptN/15-4 10 108494502 ns/op 33559027 B/op 22 allocs/op
+BenchmarkScryptN/16-4 5 217347137 ns/op 67113465 B/op 22 allocs/op ... 217ms+67MiB
+BenchmarkScryptN/17-4 3 449680138 ns/op 134222362 B/op 22 allocs/op
+BenchmarkScryptN/18-4 2 867481653 ns/op 268440064 B/op 22 allocs/op
+BenchmarkScryptN/19-4 1 1738085333 ns/op 536875536 B/op 23 allocs/op
+BenchmarkScryptN/20-4 1 3508224867 ns/op 1073746448 B/op 23 allocs/op
+BenchmarkScryptN/21-4 1 9536561994 ns/op 2147488272 B/op 23 allocs/op
+BenchmarkScryptN/22-4 1 16937072495 ns/op 4294971920 B/op 23 allocs/op
PASS
-BenchmarkScrypt10-2 300 6021435 ns/op ... 6ms
-BenchmarkScrypt11-2 100 11861460 ns/op
-BenchmarkScrypt12-2 100 23420822 ns/op
-BenchmarkScrypt13-2 30 47666518 ns/op
-BenchmarkScrypt14-2 20 92561590 ns/op ... 92ms
-BenchmarkScrypt15-2 10 183971593 ns/op
-BenchmarkScrypt16-2 3 368506365 ns/op
-BenchmarkScrypt17-2 2 755502608 ns/op ... 755ms
-ok github.com/rfjakob/gocryptfs/v2/cryptfs 18.772s
+ok github.com/rfjakob/gocryptfs/v2/internal/configfile 47.545s
*/
-func benchmarkScryptN(n int, b *testing.B) {
+func BenchmarkScryptN(b *testing.B) {
+ for n := 10; n <= 20; n++ {
+ b.Run(fmt.Sprintf("%d", n), func(b *testing.B) {
+ benchmarkScryptN(b, n)
+ })
+ }
+}
+
+func benchmarkScryptN(b *testing.B, n int) {
kdf := NewScryptKDF(n)
for i := 0; i < b.N; i++ {
kdf.DeriveKey(testPw)
}
-}
-
-func BenchmarkScrypt10(b *testing.B) {
- benchmarkScryptN(10, b)
-}
-
-func BenchmarkScrypt11(b *testing.B) {
- benchmarkScryptN(11, b)
-}
-
-func BenchmarkScrypt12(b *testing.B) {
- benchmarkScryptN(12, b)
-}
-
-func BenchmarkScrypt13(b *testing.B) {
- benchmarkScryptN(13, b)
-}
-
-func BenchmarkScrypt14(b *testing.B) {
- benchmarkScryptN(14, b)
-}
-
-func BenchmarkScrypt15(b *testing.B) {
- benchmarkScryptN(15, b)
-}
-
-func BenchmarkScrypt16(b *testing.B) {
- benchmarkScryptN(16, b)
-}
-
-func BenchmarkScrypt17(b *testing.B) {
- benchmarkScryptN(17, b)
+ b.ReportAllocs()
}