Java detailed explanation of one-way encryption-MD5, SHA and HMAC and simple implementation example code

This article mainly introduces Java's detailed explanation of one-way encryption--MD5, SHA and HMAC and simple implementation examples. Friends in need can refer to

Java's detailed explanation of one-way encryption--MD5, SHA and HMAC and simple implementation examples

Summary:

The three encryption algorithms of MD5, SHA, and HMAC can be said to be non-reversible encryption, which is an encryption method that cannot be decrypted.

MD5

MD5 is Message-Digest Algorithm 5 (Message-Digest Algorithm 5), which is used to ensure complete and consistent information transmission. MD5 is an algorithm that inputs information of variable length and outputs a fixed length of 128-bits.

The MD5 algorithm has the following characteristics:

1. Compressibility: For data of any length, the length of the calculated MD5 value is fixed.
2. Easy to calculate: It is easy to calculate the MD5 value from the original data.
3. Anti-modification: If any changes are made to the original data, even if only 1 byte is modified, the resulting MD5 value will be very different.
4. Strong anti-collision: Given the original data and its MD5 value, it is very difficult to find data with the same MD5 value (ie, forged data).

MD5 is also widely used for login authentication of operating systems, such as Unix, various BSD system login passwords, digital signatures and many other aspects. For example, in a Unix system, the user's password is stored in the file system after hashing using MD5 (or other similar algorithms). When the user logs in, the system performs an MD5 hash operation on the password entered by the user, and then compares it with the MD5 value stored in the file system to determine whether the entered password is correct. Through such steps, the system can determine the legitimacy of the user's login to the system without knowing the clear code of the user's password. This prevents the user's password from becoming known to users with system administrator rights. MD5 maps a "byte string" of any length into a 128-bit large integer, and it is very difficult to reverse the original string through this 128-bit.

SHA

SHA (Secure Hash Algorithm, secure hash algorithm), digital signature and other important tools in cryptography applications, are widely used It is widely used in information security fields such as e-commerce. Although both SHA and MD5 have been cracked through collision methods, SHA is still a recognized secure encryption algorithm and is more secure than MD5.

The length defined by SHA

The relay hash value (internal state) in the following table represents the compressed hash of each data block The relay value (internal hash sum).

##80+,and,or, xor,shr,rotrhas not appeared yet

Algorithm	Output hash value length (bits)	Relay Hash value length (bits)	Data block length (bits)	Maximum input message length (bits)	One Word length (bits)	Number of cycles	Operators used	Collision attack
SHA-0	160	160	512	264 − 1	32	80	+,and,or,xor,rotl	is
SHA-1	160	160	512	264 − 1	32	80	+,and,or,xor,rotl	There is a 263 attack
SHA -256/224	256/224	256	512	264 − 1	32	64	+,and,or,xor,shr,rotr	has not appeared yet
SHA-512/384	512/ 384	512	1024	2128 − 1	64

HMAC

HMAC(Hash Message Authentication Code ), hash message authentication code, key-based Hash algorithm authentication protocol. The principle of message authentication code is to use a public function and key to generate a fixed-length value as an authentication identifier, and use this identifier to authenticate the integrity of the message. A secret key is used to generate a small, fixed-size block of data, the MAC, which is added to the message and then transmitted. The receiver uses the key shared with the sender for authentication and authentication.

Java Example

package com.zzj.encryption; 
 
import java.security.MessageDigest; 
 
import javax.crypto.Mac; 
import javax.crypto.SecretKey; 
import javax.crypto.spec.SecretKeySpec; 
 
import org.apache.commons.codec.binary.Base64; 
 
/** 
 * 单向加密（非可逆加密） 
 * @author lenovo 
 * 
 */ 
public class OneWayEncryption { 
  static final String ALGORITHM_MD5 = "MD5"; 
  static final String ALGORITHM_SHA = "SHA"; 
  /** 
   * MAC算法可选以下多种算法 
   * <pre class="brush:php;toolbar:false"> 
   * HmacMD5 
   * HmacSHA1 
   * HmacSHA256 
   * HmacSHA384 
   * HmacSHA512 
   * 

*/ static final String ALGORITHM_MAC = "HmacMD5"; /** 密钥 **/ static final String MAC_KEY = "abcdef"; public static void main(String[] args) throws Exception { String source = "我是程序猿！我很骄傲！"; // MD5加密 printBase64(encryptionMD5(source)); // SHA加密 printBase64(encryptionSHA(source)); // HMAC加密 printBase64(encryptionHMAC(source)); } static void printBase64(byte[] out) throws Exception { System.out.println(encodeBase64(out)); } /** * MD5加密 * @param source * @return * @throws Exception */ static byte[] encryptionMD5(String source) throws Exception { MessageDigest md = MessageDigest.getInstance(ALGORITHM_MD5); md.update(source.getBytes("UTF-8")); return md.digest(); } /** * SHA加密 * @param source * @return * @throws Exception */ static byte[] encryptionSHA(String source) throws Exception { MessageDigest md = MessageDigest.getInstance(ALGORITHM_SHA); md.update(source.getBytes("UTF-8")); return md.digest(); } /** * HMAC加密 * @return * @throws Exception */ static byte[] encryptionHMAC(String source) throws Exception { SecretKey secretKey = new SecretKeySpec(MAC_KEY.getBytes("UTF-8"), ALGORITHM_MAC); Mac mac = Mac.getInstance(ALGORITHM_MAC); mac.init(secretKey); mac.update(source.getBytes("UTF-8")); return mac.doFinal(); } /** * base64编码 * @param source * @return * @throws Exception */ static String encodeBase64(byte[] source) throws Exception{ return new String(Base64.encodeBase64(source), "UTF-8"); } }

Result:

1cNbZhnhFsFV3BFPLA71wA== 
kl5KI61Xq44E/SzSPa2sUntMAEc= 
JF2v/u9td5l8yGAImNvTZw==

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