数字签名-MD5

MD5是信息摘要的意思，报文产生摘要是唯一的（1:1），而且是单向的（通过摘要反推不出源报文）

java中的java.security.MessageDigest类，参考MessageDigest的功能及用法

1 public static byte[] getMD5Mac(byte[] bySourceByte) { 2 byte[] byDisByte; 3 MessageDigest md; 4 try { 5 md = MessageDigest.getInstance("MD5"); 6 md.reset(); 7 md.update(bySourceByte); 8 byDisByte = md.digest(); 9 } catch (NoSuchAlgorithmException n) { 10 return (null); 11 } 12 return (byDisByte); 13 }

MessageDigest 是 statefull，电话 MessageDigest.update (byte [] 输入） 累积文摘更新，直到我们称之为 MessageDigest.digest。运行此测试，以确保:

    1 MessageDigest md1 = MessageDigest.getInstance("MD5"); 2 md1.update(new byte[] {1, 2}); 3 md1.update(new byte[] {3, 4}); 4 System.out.println(Arrays.toString(md1.digest())); 5 6 MessageDigest md2 = MessageDigest.getInstance("MD5"); 7 md2.update(new byte[] {1, 2, 3, 4}); 8 System.out.println(Arrays.toString(md2.digest())); 输出: [8, -42, -64, 90, 33, 81, 42, 121, -95, -33, -21, -99, 42, -113, 38, 47] [8, -42, -64, 90, 33, 81, 42, 121, -95, -33, -21, -99, 42, -113, 38, 47]

生成的摘要是byte[]类型的，需要转换成String

1 public static String bintoascii(byte[] bySourceByte) { 2 int len, i; 3 byte tb; 4 char high, tmp, low; 5 len = bySourceByte.length; 6 StringBuilder sb = new StringBuilder(len); 7 for (i = 0; i < len; i++) { 8 tb = bySourceByte[i]; 9 tmp = (char) ((tb >>> 4) & 0x000f); 10 if (tmp >= 10) 11 high = (char) ('a' + tmp - 10); 12 else 13 high = (char) ('0' + tmp); 14 sb.append(high); 15 tmp = (char) (tb & 0x000f); 16 if (tmp >= 10) 17 low = (char) ('a' + tmp - 10); 18 else 19 low = (char) ('0' + tmp); 20 sb.append(low); 21 } 22 return sb.toString(); 23 }

 

转载于:https://www.cnblogs.com/zhima-hu/p/7637674.html

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