java md5加密解密

法一：只加密

1. import java.security.*;
2. import java.security.spec.*;
3. class MD5_test {
4. public final static String MD5(String s) {
5. char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
6. 'a', 'b', 'c', 'd', 'e', 'f' };
7. try {
8. byte[] strTemp = s.getBytes();
9. MessageDigest mdTemp = MessageDigest.getInstance("MD5");
10. mdTemp.update(strTemp);
11. byte[] md = mdTemp.digest();
12. int j = md.length;
13. char str[] = new char[j * 2];
14. int k = 0;
15. for (int i = 0; i < j; i++) {
16. byte byte0 = md[i];
17. str[k++] = hexDigits[byte0 >>> 4 & 0xf];
18. str[k++] = hexDigits[byte0 & 0xf];
19. }
20. return new String(str);
21. } catch (Exception e) {
22. return null;
23. }
24. }
25. public static void main(String[] args) {
26. // MD5_Test aa = new MD5_Test();
27. System.out.print(MD5_test.MD5("b"));
28. }
29. }

方法二：加密与解密

[c-sharp] view plain copy

1. import java.security.MessageDigest;
2. public class MD5andKL {
3. // MD5加码。32位
4. public static String MD5(String inStr) {
5. MessageDigest md5 = null;
6. try {
7. md5 = MessageDigest.getInstance("MD5");
8. } catch (Exception e) {
9. System.out.println(e.toString());
10. e.printStackTrace();
11. return "";
12. }
13. char[] charArray = inStr.toCharArray();
14. byte[] byteArray = new byte[charArray.length];
15. for (int i = 0; i < charArray.length; i++)
16. byteArray[i] = (byte) charArray[i];
17. byte[] md5Bytes = md5.digest(byteArray);
18. StringBuffer hexValue = new StringBuffer();
19. for (int i = 0; i < md5Bytes.length; i++) {
20. int val = ((int) md5Bytes[i]) & 0xff;
21. if (val < 16)
22. hexValue.append("0");
23. hexValue.append(Integer.toHexString(val));
24. }
25. return hexValue.toString();
26. }
27. // 可逆的加密算法
28. public static String KL(String inStr) {
29. // String s = new String(inStr);
30. char[] a = inStr.toCharArray();
31. for (int i = 0; i < a.length; i++) {
32. a[i] = (char) (a[i] ^ 't');
33. }
34. String s = new String(a);
35. return s;
36. }
37. // 加密后解密
38. public static String JM(String inStr) {
39. char[] a = inStr.toCharArray();
40. for (int i = 0; i < a.length; i++) {
41. a[i] = (char) (a[i] ^ 't');
42. }
43. String k = new String(a);
44. return k;
45. }
46. // 测试主函数
47. public static void main(String args[]) {
48. String s = new String("a");
49. System.out.println("原始：" + s);
50. System.out.println("MD5后：" + MD5(s));
51. System.out.println("MD5后再加密：" + KL(MD5(s)));
52. System.out.println("解密为MD5后的：" + JM(KL(MD5(s))));
53. }
54. }