对数据进行哈希加盐加密

介绍

哈希加盐是在对密码进行哈希加密的前提下，为了防止查表法对密码的暴力破解，因此需要对密码进行更强的加密，它利用的核心思想是在对真实密码进行加密前，首先生成一个随机的定长字符串，这个字符串就是所谓的“盐”，然后与真实密码连接起来进行哈希加密，这样查表法就不灵了，但我们需要额外的空间来记录这个盐值，为了后来解密需要

在进行密码验证时，需要先从数据库中获得对应的盐值，然后与输入的密码拼接起来进行哈希加密，最后与数据库存储的哈希加盐加密的字符串进行对比。

具体贴实现代码

import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import java.math.BigInteger;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;

public class PasswordHash {
public static final String PBKDF2_ALGORITHM = "PBKDF2WithHmacSHA1";

// The following constants may be changed without breaking existing hashes.
public static final int SALT_BYTE_SIZE = 24;
public static final int HASH_BYTE_SIZE = 24;
public static final int PBKDF2_ITERATIONS = 1000;

public static final int ITERATION_INDEX = 0;
public static final int SALT_INDEX = 1;
public static final int PBKDF2_INDEX = 2;

/**
* Returns a salted PBKDF2 hash of the password.
* 返回已加盐的PBKDF2哈希值
* 格式 迭代次数:盐值:哈希值
* @param password the password to hash
* @return a salted PBKDF2 hash of the password
*/
public static String createPasswordHash(String password)throws NoSuchAlgorithmException, InvalidKeySpecException {
return createPasswordHash(password.toCharArray());
}

/**
* Returns a salted PBKDF2 hash of the password.
*
* @param password  the password to hash
* @return a salted PBKDF2 hash of the password
*/
public static String createPasswordHash(char[] password)throws NoSuchAlgorithmException, InvalidKeySpecException {
byte[] salt=getSalt();
// Hash the password
byte[] hash = pbkdf2(password, salt, PBKDF2_ITERATIONS, HASH_BYTE_SIZE);
// format iterations:salt:hash
return PBKDF2_ITERATIONS + ":" + toHex(salt) + ":" + toHex(hash);
}
/**
* Validates a password using a hash.
*
* @param password      the password to check
* @param correctHash   the hash of the valid password
* @return true if the password is correct, false if not
*/
public static boolean validatePassword(String password, String correctHash)
throws NoSuchAlgorithmException, InvalidKeySpecException {
return validatePassword(password.toCharArray(), correctHash);
}

/**
* Validates a password using a hash.
* 验证密码
* @param password      the password to check
* @param correctHash   the hash of the valid password
* @return true if the password is correct, false if not
*/
public static boolean validatePassword(char[] password, String correctHash)
throws NoSuchAlgorithmException, InvalidKeySpecException {
// Decode the hash into its parameters
String[] params = correctHash.split(":");
int iterations = Integer.parseInt(params[ITERATION_INDEX]);
byte[] salt = fromHex(params[SALT_INDEX]);
byte[] hash = fromHex(params[PBKDF2_INDEX]);
// Compute the hash of the provided password, using the same salt,
// iteration count, and hash length
byte[] testHash = pbkdf2(password, salt, iterations, hash.length);
// Compare the hashes in constant time. The password is correct if
// both hashes match.
return slowEquals(hash, testHash);
}

/**
* 生成盐值
* @return
* @throws NoSuchAlgorithmException
*/
public static byte[] getSalt() throws NoSuchAlgorithmException
{
SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
byte[] salt = new byte[SALT_BYTE_SIZE];
sr.nextBytes(salt);
return salt;
}
//==========
4000
==============private method============================
/**
* Compares two byte arrays in length-constant time. This comparison method
* is used so that password hashes cannot be extracted from an on-line
* system using a timing attack and then attacked off-line.
*
* @param a
*            the first byte array
* @param b
*            the second byte array
* @return true if both byte arrays are the same, false if not
*/
private static boolean slowEquals(byte[] a, byte[] b) {
int diff = a.length ^ b.length;
for (int i = 0; i < a.length && i < b.length; i++)
diff |= a[i] ^ b[i];
return diff == 0;
}

/**
* 完成PBKDF2 加密密码
* @param password      密码
* @param salt the      盐值
* @param iterations    迭代次数(缓慢因子)
* @param bytes         hash（密钥）的字节长度
* @return the PBDKF2 hash of the password
*/
private static byte[] pbkdf2(char[] password, byte[] salt, int iterations,
int bytes) throws NoSuchAlgorithmException, InvalidKeySpecException {
PBEKeySpec spec = new PBEKeySpec(password, salt, iterations, bytes * 8);
SecretKeyFactory skf = SecretKeyFactory.getInstance(PBKDF2_ALGORITHM);
return skf.generateSecret(spec).getEncoded();
}

/**
* 十六进制字符的字符串转换成字节数组。
*
* @param hex the hex string
* @return the hex string decoded into a byte array
*/
private static byte[] fromHex(String hex) {
byte[] binary = new byte[hex.length() / 2];
for (int i = 0; i < binary.length; i++) {
binary[i] = (byte) Integer.parseInt(
hex.substring(2 * i, 2 * i + 2), 16);
}
return binary;
}

/**
* 将字节数组转换为十六进制字符串。
* @param array the byte array to convert
* @return a length*2 character string encoding the byte array
*/
private static String toHex(byte[] array) {
BigInteger bi = new BigInteger(1, array);
String hex = bi.toString(16);
int paddingLength = (array.length * 2) - hex.length();
if (paddingLength > 0)
return String.format("%0" + paddingLength + "d", 0) + hex;
else
return hex;
}

public static void main(String[] args) {
String password="12345";
String salt;
try {
salt = getSalt().toString();
String hash=createPasswordHash(password);
System.out.println(hash);
long begin=System.currentTimeMillis();
System.out.println(validatePassword(password, hash));
System.out.println("time:"+(System.currentTimeMillis()-begin));
} catch (Exception e) {
}
}

}