我怎样才能在Java中散列密码？
我需要散列密码以存储在数据库中。 我怎样才能在Java中做到这一点？
我希望获取纯文本密码，添加一个随机盐，然后将salt和哈希密码存储在数据库中。
然后，当用户想要登录时，我可以提取他们提交的密码，从他们的账户信息中添加随机盐，对其进行散列，并查看它是否与存储的散列密码等同于他们的账户信息。
实际上，您可以使用内置于Java运行时的设施来执行此操作。 Java 6中的SunJCE支持PBKDF2，这是一种用于密码散列的好算法。
byte[] salt = new byte[16];
random.nextBytes(salt);
KeySpec spec = new PBEKeySpec("password".toCharArray(), salt, 65536, 128);
SecretKeyFactory f = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
byte[] hash = f.generateSecret(spec).getEncoded();
Base64.Encoder enc = Base64.getEncoder();
System.out.printf("salt: %s%n", enc.encodeToString(salt));
System.out.printf("hash: %s%n", enc.encodeToString(hash));
以下是可用于PBKDF2密码认证的实用程序类：
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;
import java.util.Arrays;
import java.util.Base64;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
/**
* Hash passwords for storage, and test passwords against password tokens.
*
* Instances of this class can be used concurrently by multiple threads.
*
* @author erickson
* @see <a href="http://stackoverflow.com/a/2861125/3474">StackOverflow</a>
*/
public final class PasswordAuthentication
{
/**
* Each token produced by this class uses this identifier as a prefix.
*/
public static final String ID = "$31$";
/**
* The minimum recommended cost, used by default
*/
public static final int DEFAULT_COST = 16;
private static final String ALGORITHM = "PBKDF2WithHmacSHA1";
private static final int SIZE = 128;
private static final Pattern layout = Pattern.compile("$31$(dd?)$(.{43})");
private final SecureRandom random;
private final int cost;
public PasswordAuthentication()
{
this(DEFAULT_COST);
}
/**
* Create a password manager with a specified cost
*
* @param cost the exponential computational cost of hashing a password, 0 to 30
*/
public PasswordAuthentication(int cost)
{
iterations(cost); /* Validate cost */
this.cost = cost;
this.random = new SecureRandom();
}
private static int iterations(int cost)
{
if ((cost < 0) || (cost > 30))
throw new IllegalArgumentException("cost: " + cost);
return 1 << cost;
}
/**
* Hash a password for storage.
*
* @return a secure authentication token to be stored for later authentication
*/
public String hash(char[] password)
{
byte[] salt = new byte[SIZE / 8];
random.nextBytes(salt);
byte[] dk = pbkdf2(password, salt, 1 << cost);
byte[] hash = new byte[salt.length + dk.length];
System.arraycopy(salt, 0, hash, 0, salt.length);
System.arraycopy(dk, 0, hash, salt.length, dk.length);
Base64.Encoder enc = Base64.getUrlEncoder().withoutPadding();
return ID + cost + '$' + enc.encodeToString(hash);
}
/**
* Authenticate with a password and a stored password token.
*
* @return true if the password and token match
*/
public boolean authenticate(char[] password, String token)
{
Matcher m = layout.matcher(token);
if (!m.matches())
throw new IllegalArgumentException("Invalid token format");
int iterations = iterations(Integer.parseInt(m.group(1)));
byte[] hash = Base64.getUrlDecoder().decode(m.group(2));
byte[] salt = Arrays.copyOfRange(hash, 0, SIZE / 8);
byte[] check = pbkdf2(password, salt, iterations);
int zero = 0;
for (int idx = 0; idx < check.length; ++idx)
zero |= hash[salt.length + idx] ^ check[idx];
return zero == 0;
}
private static byte[] pbkdf2(char[] password, byte[] salt, int iterations)
{
KeySpec spec = new PBEKeySpec(password, salt, iterations, SIZE);
try {
SecretKeyFactory f = SecretKeyFactory.getInstance(ALGORITHM);
return f.generateSecret(spec).getEncoded();
}
catch (NoSuchAlgorithmException ex) {
throw new IllegalStateException("Missing algorithm: " + ALGORITHM, ex);
}
catch (InvalidKeySpecException ex) {
throw new IllegalStateException("Invalid SecretKeyFactory", ex);
}
}
/**
* Hash a password in an immutable {@code String}.
*
* <p>Passwords should be stored in a {@code char[]} so that it can be filled
* with zeros after use instead of lingering on the heap and elsewhere.
*
* @deprecated Use {@link #hash(char[])} instead
*/
@Deprecated
public String hash(String password)
{
return hash(password.toCharArray());
}
/**
* Authenticate with a password in an immutable {@code String} and a stored
* password token.
*
* @deprecated Use {@link #authenticate(char[],String)} instead.
* @see #hash(String)
*/
@Deprecated
public boolean authenticate(String password, String token)
{
return authenticate(password.toCharArray(), token);
}
}
这里有两个方法完全实现你想要的完整实现 ：
String getSaltedHash(String password)
boolean checkPassword(String password, String stored)
问题是，即使攻击者能够访问数据库和源代码，密码仍然是安全的。
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import java.security.SecureRandom;
import org.apache.commons.codec.binary.Base64;
public class Password {
// The higher the number of iterations the more
// expensive computing the hash is for us and
// also for an attacker.
private static final int iterations = 20*1000;
private static final int saltLen = 32;
private static final int desiredKeyLen = 256;
/** Computes a salted PBKDF2 hash of given plaintext password
suitable for storing in a database.
Empty passwords are not supported. */
public static String getSaltedHash(String password) throws Exception {
byte[] salt = SecureRandom.getInstance("SHA1PRNG").generateSeed(saltLen);
// store the salt with the password
return Base64.encodeBase64String(salt) + "$" + hash(password, salt);
}
/** Checks whether given plaintext password corresponds
to a stored salted hash of the password. */
public static boolean check(String password, String stored) throws Exception{
String[] saltAndPass = stored.split("$");
if (saltAndPass.length != 2) {
throw new IllegalStateException(
"The stored password have the form 'salt$hash'");
}
String hashOfInput = hash(password, Base64.decodeBase64(saltAndPass[0]));
return hashOfInput.equals(saltAndPass[1]);
}
// using PBKDF2 from Sun, an alternative is https://github.com/wg/scrypt
// cf. http://www.unlimitednovelty.com/2012/03/dont-use-bcrypt.html
private static String hash(String password, byte[] salt) throws Exception {
if (password == null || password.length() == 0)
throw new IllegalArgumentException("Empty passwords are not supported.");
SecretKeyFactory f = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
SecretKey key = f.generateSecret(new PBEKeySpec(
password.toCharArray(), salt, iterations, desiredKeyLen)
);
return Base64.encodeBase64String(key.getEncoded());
}
}
我们存储'salt$iterated_hash(password, salt)' 。 盐是32个随机字节，其目的是如果两个不同的人选择相同的密码，存储的密码仍然会看起来不同。
iterated_hash基本上是hash(hash(hash(... hash(password, salt) ...))) ，它使得访问数据库的潜在攻击者可以猜测密码，哈希以及查找在数据库中加入哈希。 每次用户登录时都必须计算这个iterated_hash ，但与花费近100％时间计算哈希值的攻击者相比，这不会花费太多。
BCrypt是一个非常好的库，它有一个Java端口。
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