diff --git a/src/asses/one.go b/src/asses/one.go
index 2785219..7ad908b 100644
--- a/src/asses/one.go
+++ b/src/asses/one.go
@@ -2,9 +2,42 @@ package asses
 
 import (
 	"context"
+	"crypto/md5"
+	"encoding/base64"
 	"io"
+	"math/rand"
+	"os"
+	"time"
 )
 
 func One(ctx context.Context, p string) error {
+	if last, err := checkLast(ctx, p); err != nil {
+		return err
+	} else if last.T.IsZero() {
+	} else if cksum, err := cksum(ctx, p); err != nil {
+		return err
+	} else if cksum != last.Cksum {
+	} else if time.Since(last.T) < 20+time.Duration(rand.Int()%10)*24*time.Hour {
+		return nil
+	}
+
 	return io.EOF
+
+	cksum, err := cksum(ctx, p)
+	if err != nil {
+		return err
+	}
+	return checked(ctx, p, cksum)
+}
+
+func cksum(ctx context.Context, p string) (string, error) {
+	f, err := os.Open(p)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	hasher := md5.New()
+	_, err = io.Copy(hasher, f)
+	return base64.StdEncoding.EncodeToString(hasher.Sum(nil)), err
 }