diff --git a/go.mod b/go.mod
index 1ee493e..268edae 100644
--- a/go.mod
+++ b/go.mod
@@ -2,7 +2,10 @@ module show-rss
 
 go 1.23.3
 
-require modernc.org/sqlite v1.37.0
+require (
+	golang.org/x/time v0.11.0
+	modernc.org/sqlite v1.37.0
+)
 
 require (
 	github.com/PuerkitoBio/goquery v1.8.0 // indirect
diff --git a/go.sum b/go.sum
index 94dad8c..7750408 100644
--- a/go.sum
+++ b/go.sum
@@ -59,6 +59,8 @@ golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9sn
 golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/text v0.5.0 h1:OLmvp0KP+FVG99Ct/qFiL/Fhk4zp4QQnZ7b2U+5piUM=
 golang.org/x/text v0.5.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
+golang.org/x/time v0.11.0 h1:/bpjEDfN9tkoN/ryeYHnv5hcMlc8ncjMcM4XBk5NWV0=
+golang.org/x/time v0.11.0/go.mod h1:CDIdPxbZBQxdj6cxyCIdrNogrJKMJ7pr37NYpMcMDSg=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.31.0 h1:0EedkvKDbh+qistFTd0Bcwe/YLh4vHwWEkiI0toFIBU=
 golang.org/x/tools v0.31.0/go.mod h1:naFTU+Cev749tSJRXJlna0T3WxKvb1kWEx15xA4SdmQ=
diff --git a/src/asses/one.go b/src/asses/one.go
index 373ad4f..03911f6 100644
--- a/src/asses/one.go
+++ b/src/asses/one.go
@@ -10,6 +10,7 @@ import (
 	"math/rand"
 	"os"
 	"path"
+	"show-rss/src/slow"
 	"time"
 )
 
@@ -31,7 +32,7 @@ func One(ctx context.Context, p string) error {
 
 	if err := func() error {
 		if len(last.Cksum) > 0 {
-			cksum, err := Cksum(p)
+			cksum, err := Cksum(ctx, p)
 			if err != nil {
 				return err
 			}
@@ -52,7 +53,7 @@ func One(ctx context.Context, p string) error {
 		return err
 	}
 
-	cksum, err := Cksum(p)
+	cksum, err := Cksum(ctx, p)
 	if err != nil {
 		return err
 	}
@@ -63,7 +64,7 @@ func One(ctx context.Context, p string) error {
 	return checked(ctx, p, cksum, stat.ModTime())
 }
 
-func Cksum(p string) (string, error) {
+func Cksum(ctx context.Context, p string) (string, error) {
 	f, err := os.Open(p)
 	if err != nil {
 		return "", err
@@ -71,6 +72,6 @@ func Cksum(p string) (string, error) {
 	defer f.Close()
 
 	hasher := md5.New()
-	_, err = io.Copy(hasher, f)
+	_, err = io.Copy(hasher, slow.NewReader(ctx, 10_000_000, f))
 	return base64.StdEncoding.EncodeToString(hasher.Sum(nil)), err
 }
diff --git a/src/asses/one_test.go b/src/asses/one_test.go
index ca5f175..0777525 100644
--- a/src/asses/one_test.go
+++ b/src/asses/one_test.go
@@ -17,7 +17,7 @@ func TestOne(t *testing.T) {
 	p := path.Join(d, "f.mkv")
 	os.WriteFile(p, b, os.ModePerm)
 
-	cksum, _ := asses.Cksum(p)
+	cksum, _ := asses.Cksum(context.Background(), p)
 
 	if err := asses.One(ctx, p); err != nil {
 		t.Fatal(err)
@@ -31,7 +31,7 @@ func TestOne(t *testing.T) {
 		t.Fatalf("no new srt: %v", err)
 	}
 
-	newCksum, _ := asses.Cksum(p)
+	newCksum, _ := asses.Cksum(context.Background(), p)
 	if cksum == newCksum {
 		t.Fatalf("cksum unchanged")
 	}