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));
这是一个可用于PBKDF2密码验证的实用程序类:
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\\$(\\d\\d?)\\$(.{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);
}
}
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[] saltAndHash = stored.split("\\$");
if (saltAndHash.length != 2) {
throw new IllegalStateException(
"The stored password must have the form 'salt$hash'");
}
String hashOfInput = hash(password, Base64.decodeBase64(saltAndHash[0]));
return hashOfInput.equals(saltAndHash[1]);
}
// using PBKDF2 from Sun, an alternative is https://github.com/wg/scrypt
// cf. http://www.unlimitednovelty.com/2012/03/dont-use-bcrypt.html
private static String hash(String password, byte[] salt) throws Exception {
if (password == null || password.length() == 0)
throw new IllegalArgumentException("Empty passwords are not supported.");
SecretKeyFactory f = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
SecretKey key = f.generateSecret(new PBEKeySpec(
password.toCharArray(), salt, iterations, desiredKeyLen));
return Base64.encodeBase64String(key.getEncoded());
}
}
10 回答
虽然已经提到NIST recommendation PBKDF2,但我想指出从2013年到2015年有一个公共password hashing competition . 最后, Argon2 被选为推荐的密码哈希函数 .
您可以使用原始(本机C)库的相当好的Java binding .
在平均用例中,如果您选择PBKDF2而不是Argon2,反之亦然,从安全角度来看,我认为不重要 . 如果您有强大的安全要求,我建议您在评估中考虑Argon2 .
有关密码散列函数安全性的更多信息,请参见security.se .
实际上,您可以使用Java运行时内置的工具来执行此操作 . Java 6中的SunJCE支持PBKDF2,这是一种用于密码散列的好算法 .
这是一个可用于PBKDF2密码验证的实用程序类:
这是一个 complete implementation ,有两种方法正是你想要的:
关键是即使攻击者可以访问您的数据库和源代码,密码仍然是安全的 .
我们正在存储
'salt$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,存储的密码仍然会有所不同 .iterated_hash
,基本上是hash(hash(hash(... hash(password, salt) ...)))
,对于有权访问您的数据库的潜在攻击者猜测密码,散列它们以及查找数据库中的哈希值非常昂贵 . 每次用户登录时都必须计算这个iterated_hash
,但与花费近100%的时间计算哈希的攻击者相比,它不会花费太多 .BCrypt是一个非常好的图书馆,它有一个Java port .
您可以使用MessageDigest计算哈希值,但这在安全性方面是错误的 . 哈希不能用于存储密码,因为它们很容易破碎 .
您应该使用其他算法,如bcrypt,PBKDF2和scrypt来存储密码 . See here .
您可以使用OWASP库描述的Shiro库(以前为JSecurity)implementation .
它看起来像JASYPT库有similar utility .
除了其他答案中提到的bcrypt和PBKDF2,我建议看scrypt
不建议使用MD5和SHA-1,因为它们相对较快,因此使用“每小时租金”分布式计算(例如EC2)或现代高端GPU可以使用强力/字典攻击以相对低的成本和合理的方式“破解”密码时间 .
如果必须使用它们,那么至少要对算法进行预定义的重复次数(1000) .
如需更多信息,请点击此处:https://security.stackexchange.com/questions/211/how-to-securely-hash-passwords
在这里:http://codahale.com/how-to-safely-store-a-password/(批评SHA家族,MD5等密码哈希目的)
在这里:http://www.unlimitednovelty.com/2012/03/dont-use-bcrypt.html(批评bcrypt并推荐scrypt和PBKDF2)
完全同意埃里克森的观点,即 PBKDF2 就是答案 .
如果您没有该选项,或者只需要使用哈希,那么Apache Commons DigestUtils比正确获取JCE代码要容易得多:https://commons.apache.org/proper/commons-codec/apidocs/org/apache/commons/codec/digest/DigestUtils.html
如果您使用哈希,请使用sha256或sha512 . 此页面提供了有关密码处理和散列的良好建议(请注意,它不建议使用散列处理密码):http://www.daemonology.net/blog/2009-06-11-cryptographic-right-answers.html
这里有两个MD5散列和其他散列方法的链接:
Javadoc API:http://java.sun.com/j2se/1.4.2/docs/api/java/security/MessageDigest.html
教程:http://www.twmacinta.com/myjava/fast_md5.php
在所有标准哈希方案中,LDAP ssha是最安全的哈希方案,
http://www.openldap.org/faq/data/cache/347.html
我只会遵循那里指定的算法并使用MessageDigest来执行哈希 .
您需要按照建议将salt存储在数据库中 .