信息计算2019级2班11号谢春晖

谢春晖

4月19日和4月22日慕课学习截图:

谢春晖

4月29日慕课截图：

谢春晖

5月3日慕课截图：

谢春晖

作业：

1. import java.security.*;
   
2. import java.security.interfaces.*;
   
3. import java.io.*;
   
4. import java.math.*;
   
5. import java.util.Scanner;
   
6. public class rsa{
   
7. public rsa() {
   
8. }
   
9. public static void generateKey() {
   
10. try {
    
11. KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
    
12. kpg.initialize(1024);
    
13. KeyPair kp = kpg.genKeyPair();
    
14. PublicKey pbkey = kp.getPublic();
    
15. PrivateKey prkey = kp.getPrivate();
    
16. // 保存公钥
    
17. FileOutputStream f1 = new FileOutputStream("pubkey.dat");
    
18. ObjectOutputStream b1 = new ObjectOutputStream(f1);
    
19. b1.writeObject(pbkey);
    
20. // 保存私钥
    
21. FileOutputStream f2 = new FileOutputStream("privatekey.dat");
    
22. ObjectOutputStream b2 = new ObjectOutputStream(f2);
    
23. b2.writeObject(prkey);
    
24. } catch (Exception e) {
    
25. }}
    
26. public static void encrypt() throws Exception {
    
27. Scanner scan = new Scanner(System.in);
    
28. System.out.println("请输入一个字符串:");
    
29. //System.out.println("您输入的字符串是:" + scan.next());
    
30. String s=scan.next();
    
31. System.out.println("你输入的是:"+s);
    
32. // 获取公钥及参数e,n
    
33. FileInputStream f = new FileInputStream("pubkey.dat");
    
34. ObjectInputStream b = new ObjectInputStream(f);
    
35. RSAPublicKey pbk = (RSAPublicKey) b.readObject();
    
36. BigInteger e = pbk.getPublicExponent();
    
37. BigInteger n = pbk.getModulus();
    
38. System.out.println("e= " + e);
    
39. System.out.println("n= " + n);
    
40. // 获取明文m
    
41. byte ptext[] = s.getBytes("UTF-8");
    
42. BigInteger m = new BigInteger(ptext);
    
43. // 计算密文c
    
44. BigInteger c = m.modPow(e, n);
    
45. System.out.println("c= " + c);
    
46. // 保存密文
    
47. String cs = c.toString();
    
48. BufferedWriter out =
    
49. new BufferedWriter(
    
50. new OutputStreamWriter(new FileOutputStream("encrypt.dat")));
    
51. out.write(cs, 0, cs.length());
    
52. out.close(); }
    
53. public static void decrypt() throws Exception { // 读取密文
    
54. BufferedReader in =
    
55. new BufferedReader(  new InputStreamReader(new FileInputStream("encrypt.dat")));
    
56. String ctext = in.readLine();
    
57. BigInteger c = new BigInteger(ctext);
    
58. // 读取私钥
    
59. FileInputStream f = new FileInputStream("privatekey.dat");
    
60. ObjectInputStream b = new ObjectInputStream(f);
    
61. RSAPrivateKey prk = (RSAPrivateKey) b.readObject();
    
62. BigInteger d = prk.getPrivateExponent();
    
63. // 获取私钥参数及解密
    
64. BigInteger n = prk.getModulus();
    
65. System.out.println("d= " + d);
    
66. System.out.println("n= " + n);
    
67. BigInteger m = c.modPow(d, n);
    
68. // 显示解密结果
    
69. System.out.println("m= " + m);
    
70. byte[] mt = m.toByteArray();
    
71. System.out.println("解密出来的文本是：");
    
72. for (int i = 0; i < mt.length; i++) {
    
73. System.out.print((char) mt[i]);
    
74. }
    
75. }
    
76. public static void main(String args[]) {
    
77. try {
    
78. generateKey();
    
79. encrypt();
    
80. decrypt();
    
81. } catch (Exception e) {
    
82. System.out.println(e.toString());}
    
83. }}
    

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