java.security.MessageDigest的用法

java.security.MessageDigest

MessageDigest的含义

message含义是:消息,信息

digest的含义是

digest
必应词典
n.摘要；文摘；概要；汇编
v.消化；领会；领悟；理解
海词
n. 摘要
vt. 消化；理解
vi. 消化
金山词霸
v.
消化; 理解
n.
摘要; 文摘
有道
v.
理解，领悟；消化
n.
文摘，摘要；分解物，提炼物

所以 MessageDigest 可以理解为 消息消化

额,不是.

应该是 信息摘要 或 数据摘要

它能将很大的信息(数据)(文件)通过某种算法(algorithm),简化为简短的内容, 用于判断大数据是否相同.

动态获取 MessageDigest 所支持的算法名称

java.security.Security.getAlgorithms("MessageDigest"); 可获得算法名称的Set<String>集合 , 参数为"MessageDigest",不区分大小写

java.util.Set<String> messageDigest_AlgorithmNames_Set = java.security.Security.getAlgorithms("MessageDigest"); //不区分大小写

java.util.Set<String> messageDigest_AlgorithmNames_Set = java.security.Security.getAlgorithms("messagedigest"); //不区分大小写

示例

public class Try动态获取MessageDigest支持的算法名称列表 {
	
	static Integer numA = 1;
	
	static public void main(String...arguments)throws Exception{
		
		java.util.Set<String> messageDigest_AlgorithmNames_Set = java.security.Security.getAlgorithms("messagedigest");
//		java.util.Set<String> messageDigest_AlgorithmNames_Set = java.security.Security.getAlgorithms("MessageDigest");
		
		System.out.println("MessageDigest的算法种类个数为: "+messageDigest_AlgorithmNames_Set.size() + " , 分别为👇");
		
		messageDigest_AlgorithmNames_Set.forEach(算法名称->{
			System.out.println(numA+++".\t\t"+算法名称);
		});		
	}
}

控制台输出👇 (JDK17)

MessageDigest的算法种类个数为: 13 , 分别为👇
1.		SHA3-512
2.		SHA-1
3.		SHA-384
4.		SHA3-384
5.		SHA-224
6.		SHA-512/256
7.		SHA-256
8.		MD2
9.		SHA-512/224
10.		SHA3-256
11.		SHA-512
12.		MD5
13.		SHA3-224

获取 MessageDigest 的实例

MessageDigest 的实例由 MessageDigest.getInstance(x) 方法获得;
一个MessageDigest实例只能指定一种算法;

MessageDigest md_SHA3512   = MessageDigest.getInstance("SHA3-512");
MessageDigest md_SHA1      = MessageDigest.getInstance("SHA-1");
MessageDigest md_SHA384    = MessageDigest.getInstance("SHA-384");
MessageDigest md_SHA3384   = MessageDigest.getInstance("SHA3-384");
MessageDigest md_SHA224    = MessageDigest.getInstance("SHA-224");
MessageDigest md_SHA512256 = MessageDigest.getInstance("SHA-512/256");
MessageDigest md_SHA256    = MessageDigest.getInstance("SHA-256");
MessageDigest md_MD2       = MessageDigest.getInstance("MD2");
MessageDigest md_SHA512224 = MessageDigest.getInstance("SHA-512/224");
MessageDigest md_SHA3256   = MessageDigest.getInstance("SHA3-256");
MessageDigest md_SHA512    = MessageDigest.getInstance("SHA-512");
MessageDigest md_MD5       = MessageDigest.getInstance("MD5");
MessageDigest md_SHA3224   = MessageDigest.getInstance("SHA3-224");

将byte数组计算为Hash

MessageDigest 通过 update 和 digest 方法, 将一个或多个byte[]数组计算为Hash摘要

digest(byte[] input) 是一步到位的方法, 直接计算出input数组的Hash, 但是有一个问题, 数组索引是int, int<=Integer.MAX; 大概2G多, 所以对很大的文件无能为力.

digest(byte[] input) 的源码👇

public byte[] digest(byte[] input) {
        update(input);
        return digest();
    }

可看出也是分为两步, 第一步是update(input), 将数组放入MessageDigest,
让后再digest()计算.
实际上update方法可以多次调用,
所以可以将大文件用缓存数组buffer拆分成多段用update放入
而且update有个现成的重载:update(byte[] input, int offset, int len)

示例

				FileInputStream is = new FileInputStream(pathStr);
				MessageDigest digest = MessageDigest.getInstance("SHA-256");
				
				byte[] bf = new byte[10240];
				int numRead;
				do {
				    numRead = is.read(bf);
				    if (numRead > 0) {
				        digest.update(bf, 0, numRead);
				    }
				} while (numRead != -1);
				
				is.close();

				byte[] resultByteArray = digest.digest();

得到的结果还是byte数组, 可将其转为16进制

将digest的结果数组转为16进制

假设已得到结果: resultByteArray

将其转为16进制的办法

    public static String bytesToHex(byte[] bytes) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < bytes.length; i++) {
            sb.append(String.format("%02x", bytes[i]));
        }
        return sb.toString();
    }
    String resultHex = bytesToHex(resultByteArray)

小写

public static String hexLowerCaseFromByteArray(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789abcdef";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt((b&0xff)>>>4)).append(simple.charAt(b<<28>>>28));
		}
		return sb.toString();
	}
	String resultHex = bytesToHex(resultByteArray)

大写

	public static String hexUpperCaseFromByteArray(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789ABCDEF";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt((b&0xff)>>>4)).append(simple.charAt(b<<28>>>28));
		}
		return sb.toString();
	}
	String resultHex = bytesToHex(resultByteArray)

	public static String hexLowerCaseFromByteArray2(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789abcdef";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt((b&0xff)/16)).append(simple.charAt((b&0xff)%16));
		}
		return sb.toString();
	}
	
	public static String hexUpperCaseFromByteArray2(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789ABCDEF";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt((b&0xff)/16)).append(simple.charAt((b&0xff)%16));
		}
		return sb.toString();
	}

	
	public static String hexLowerCaseFromByteArray3(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789abcdef";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt((b&255)/16)).append(simple.charAt((b&255)%16));
		}
		return sb.toString();
	}
	
	public static String hexUpperCaseFromByteArray3(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789ABCDEF";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt((b&255)/16)).append(simple.charAt((b&255)%16));
		}
		return sb.toString();
	}

	
	public static String hexLowerCaseFromByteArray4(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789abcdef";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			int i=b>=0?b:b+256;
			sb.append(simple.charAt(i/16)).append(simple.charAt(i%16));
		}
		return sb.toString();
	}
	
	public static String hexUpperCaseFromByteArray4(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789ABCDEF";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			int i=b>=0?b:b+256;
			sb.append(simple.charAt(i/16)).append(simple.charAt(i%16));
		}
		return sb.toString();
	}

	public static String hexLowerCaseFromByteArray5(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789abcdef";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt(Byte.toUnsignedInt(b)/16)).append(simple.charAt(Byte.toUnsignedInt(b)%16));
		}
		return sb.toString();
	}
	
	public static String hexUpperCaseFromByteArray5(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789ABCDEF";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt(Byte.toUnsignedInt(b)/16)).append(simple.charAt(Byte.toUnsignedInt(b)%16));
		}
		return sb.toString();
	}

测试

package 将byte数组转为16进制字符串的方法;

import java.awt.FileDialog;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.FileInputStream;
import java.security.MessageDigest;

import javax.swing.JFrame;

public class ByteArrayToHexString {
	
	public static String hexLowerCaseFromByteArray(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789abcdef";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt((b&0xff)>>>4)).append(simple.charAt(b<<28>>>28));
		}
		return sb.toString();
	}
	
	public static String hexUpperCaseFromByteArray(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789ABCDEF";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt((b&0xff)>>>4)).append(simple.charAt(b<<28>>>28));
		}
		return sb.toString();
	}
	
	
	public static String hexLowerCaseFromByteArray2(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789abcdef";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt((b&0xff)/16)).append(simple.charAt((b&0xff)%16));
		}
		return sb.toString();
	}
	
	public static String hexUpperCaseFromByteArray2(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789ABCDEF";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt((b&0xff)/16)).append(simple.charAt((b&0xff)%16));
		}
		return sb.toString();
	}
	
	
	
	public static String hexLowerCaseFromByteArray3(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789abcdef";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt((b&255)/16)).append(simple.charAt((b&255)%16));
		}
		return sb.toString();
	}
	
	public static String hexUpperCaseFromByteArray3(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789ABCDEF";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt((b&255)/16)).append(simple.charAt((b&255)%16));
		}
		return sb.toString();
	}
	
	
	public static String hexLowerCaseFromByteArray4(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789abcdef";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			int i=b>=0?b:b+256;
			sb.append(simple.charAt(i/16)).append(simple.charAt(i%16));
		}
		return sb.toString();
	}
	
	public static String hexUpperCaseFromByteArray4(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789ABCDEF";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			int i=b>=0?b:b+256;
			sb.append(simple.charAt(i/16)).append(simple.charAt(i%16));
		}
		return sb.toString();
	}
	
	
	public static String hexLowerCaseFromByteArray5(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789abcdef";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt(Byte.toUnsignedInt(b)/16)).append(simple.charAt(Byte.toUnsignedInt(b)%16));
		}
		return sb.toString();
	}
	
	public static String hexUpperCaseFromByteArray5(byte[] byteArray) {
		if(byteArray==null)return null;
		String simple = "0123456789ABCDEF";
		StringBuilder sb = new StringBuilder(byteArray.length*2);
		for(byte b : byteArray) {
			sb.append(simple.charAt(Byte.toUnsignedInt(b)/16)).append(simple.charAt(Byte.toUnsignedInt(b)%16));
		}
		return sb.toString();
	}
	
	public static String hexLowerCaseFromByteArray6(byte[] byteArray) {
		if(byteArray==null)return null;
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < byteArray.length; i++) {
            sb.append(String.format("%02x", byteArray[i]));
        }
        return sb.toString();
	}
	
	
	public static void main(String...arguments)throws Exception{
		JFrame frame = new JFrame(Thread.currentThread().getStackTrace()[1].getClassName());
		frame.addWindowListener(new WindowAdapter() {
			@Override public void windowClosing(WindowEvent ev) {System.exit(0);}
		});
		FileDialog fDialog = new FileDialog(frame);
		
		fDialog.setVisible(true);
		
		if(fDialog.getFile()!=null) {
			String pathFile = fDialog.getDirectory()+fDialog.getFile();
			FileInputStream is = new FileInputStream(pathFile);
			MessageDigest digest = MessageDigest.getInstance("SHA-256");
			
			byte[] bf = new byte[10240];
			int numRead;
			do {
			    numRead = is.read(bf);
			    if (numRead > 0) {
			        digest.update(bf, 0, numRead);
			    }
			} while (numRead != -1);
			
			is.close();

			byte[] resultByteArray = digest.digest();
			
			String result;
			
			result = hexLowerCaseFromByteArray(resultByteArray); System.out.println(result);
			result = hexUpperCaseFromByteArray(resultByteArray); System.out.println(result);
			result = hexLowerCaseFromByteArray2(resultByteArray); System.out.println(result);
			result = hexUpperCaseFromByteArray2(resultByteArray); System.out.println(result);
			result = hexLowerCaseFromByteArray3(resultByteArray); System.out.println(result);
			result = hexUpperCaseFromByteArray3(resultByteArray); System.out.println(result);
			result = hexLowerCaseFromByteArray4(resultByteArray); System.out.println(result);
			result = hexUpperCaseFromByteArray4(resultByteArray); System.out.println(result);
			result = hexLowerCaseFromByteArray5(resultByteArray); System.out.println(result);
			result = hexUpperCaseFromByteArray5(resultByteArray); System.out.println(result);
			result = hexLowerCaseFromByteArray6(resultByteArray); System.out.println(result);
		}
		
		System.exit(0);
	}
	

}

一些应用例子

例1


import java.awt.*;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.FileInputStream;
import java.security.MessageDigest;
import java.util.*;

import javax.swing.*;

//import javax.swing.JButton;

public class SHA_MD_MessageDigest_230528 extends Frame{

	/**
	 * 
	 */
	private static final long serialVersionUID = 5242216018207119189L;
	static void pln(Object o) {System.out.println(o);}
	
	public final SHA_MD_MessageDigest_230528 I;
	
	public final TextArea resultLowercaseShow = new TextArea("这里展示小写结果");
	public final TextArea resultUppercaseShow = new TextArea("这里展示大写结果");
	
	public final HashMap<String, MessageDigest> DigestGroup = new HashMap<>();
	public final LinkedHashMap<String, Panel> ButtonForComputedGroup  = new LinkedHashMap<>();
	{
		Set<String> set = java.security.Security.getAlgorithms("MessageDigest"); //获得支持的格式
		ArrayList<String> nmAl = new ArrayList<>(set);
		nmAl.sort((o1,o2)->o1.compareTo(o2));
		try {
			for(String nm : set) {
				DigestGroup.put(nm, MessageDigest.getInstance(nm));
			}
			nmAl.forEach(nm->{
				ButtonForComputedGroup.put(nm, new Btn(nm));
			});
		}catch(Exception ex) {ex.printStackTrace();}
	}
	
	
	//constructor 构造方法在此
	public SHA_MD_MessageDigest_230528() {
		I=this;
		setTitle("文件校验, 点击按钮选择文件 ");
		
		addWindowListener(new WindowAdapter() {
			@Override
			public void windowClosing(WindowEvent e) {
				I.dispose();
				System.exit(0);
			}
		});
		setLayout(new GridLayout(3, 0, 1, 3));
		
		Panel up = new Panel(); add(up); up.setBackground(Color.DARK_GRAY);
		Panel panel010 = new Panel(); add(panel010);
//		Panel panel020 = new Panel(); add(panel020);
		JPanel panel020 = new JPanel(); add(panel020);
		ButtonForComputedGroup.forEach((lb,btn)->{
			up.add(btn);
		});
		panel010.setLayout(new BorderLayout(200,200));  
		panel010.add(resultLowercaseShow);
		System.out.println(panel020.getLayout());
		panel020.setLayout(new BorderLayout());
		panel020.add(resultUppercaseShow);
		
		setBounds(258, 235, 1600, 666);
		setVisible(true);
//		show();
	}
	public static void main(String ags[]) {new SHA_MD_MessageDigest_230528();}
	
	void computed(String nm) {
		pln(nm);
		String lowercaseMapping = "0123456789abcdef" , uppercaseMapping = lowercaseMapping.toUpperCase();
		FileDialog fileDialog = new FileDialog(this, "选择要生成Hash的文件", FileDialog.LOAD);
		fileDialog.setVisible(true);
		String directoryStr = fileDialog.getDirectory() , fileStr = fileDialog.getFile();
		if(directoryStr!=null && fileStr!=null) {
			try {
				String pathStr = directoryStr+fileStr;
				resultLowercaseShow.setText("正在计算  "+pathStr+"   的"+nm+"值");
				FileInputStream is = new FileInputStream(pathStr);
				MessageDigest digest = DigestGroup.get(nm);
				
				byte[] bf = new byte[10240];
				int numRead;
				do {
				    numRead = is.read(bf);
				    if (numRead > 0) {
				        digest.update(bf, 0, numRead);
				    }
				} while (numRead != -1);
				
				is.close();
				
				
				bf = digest.digest();
				StringBuilder sb = new StringBuilder(bf.length*2);
				for(byte b : bf) {
					int idx1=(b&0xff)>>>4 , idx2=b<<28>>>28;
					pln("idx1="+idx1+"      idx2="+idx2);
					sb.append(lowercaseMapping.charAt(idx1)).append(lowercaseMapping.charAt(idx2));
				}
				String hexLower = sb.toString();
				resultLowercaseShow.setText(hexLower);
				sb = new StringBuilder(bf.length*2);
				for(byte b : bf) {
					int idx1=(b&0xff)>>>4 , idx2=b<<28>>>28;
					pln("idx1="+idx1+"      idx2="+idx2);
					sb.append(uppercaseMapping.charAt(idx1)).append(uppercaseMapping.charAt(idx2));
				}
				String hexUpper = sb.toString();
				resultUppercaseShow.setText(hexUpper);
				
				
			}catch(Throwable ex) {ex.printStackTrace(); resultLowercaseShow.setText(ex.toString()); }
		}
		
		
	}
	
	class Btn extends Panel{
		/**
		 * 镶嵌在Panel中的Button
		 */
		private static final long serialVersionUID = -3494086542207800072L;
		public final Button btn;
		Btn(String label){
			super();
			this.setBackground(Color.blue);
//			setLayout(new BorderLayout());
			setLayout(null);
			setSize(210,60);
			btn = new Button(label);
			switch (label) {
			case"MD5","SHA-256": btn.setForeground(Color.BLUE); break;
			case"SHA-512": btn.setForeground(Color.WHITE);btn.setBackground(new Color(0,168,255)); break;
			}
			btn.setBounds(5, 5, 200, 50);
			
			setFont(new Font("宋体", Font.CENTER_BASELINE, 25));
			btn.addActionListener(ev->{
				computed(btn.getActionCommand());
			});
			add(btn);
		}
		
	}

}