我一直在寻找最接近的答案是：如何生成随机字母数字字符串？
我想按照这个CrackStation教程的工作流程：
存储密码
使用CSPRNG生成一个长的随机盐。
将盐前置到密码中，并使用标准加密哈希函数（例如SHA256）进行哈希处理。
将盐和哈希值都保存在用户数据库记录中。
验证密码
从数据库中检索用户的盐和哈希值。
将盐前置到给定的密码中，并使用相同的哈希函数进行哈希处理。
将给定密码的哈希值与数据库中的哈希值进行比较。如果它们匹配，则密码正确。否则，密码不正确。
我不知道如何生成盐。我想出了如何使用MessageDigest生成哈希值。我尝试使用SecureRandom，但nextByte方法生成乱码。
编辑：我不知道该选择哪个答案，它们对我来说太复杂了，我已经决定使用jBCrypt； jBCript易于使用，背后完成所有复杂的工作。因此，我会让社区投票选出最佳答案。
受到这篇帖子和那篇帖子的启发，我使用这段代码生成和验证散列盐密码。它只使用了JDK提供的类，没有外部依赖。
流程如下：
getNextSalt 创建一个盐hash 方法来生成加盐和哈希过的密码。该方法返回一个 byte[]，您可以将其与盐一起保存在数据库中isExpectedPassword 方法来检查详细信息是否匹配/**
* A utility class to hash passwords and check passwords vs hashed values. It uses a combination of hashing and unique
* salt. The algorithm used is PBKDF2WithHmacSHA1 which, although not the best for hashing password (vs. bcrypt) is
* still considered robust and <a href="https://security.stackexchange.com/a/6415/12614"> recommended by NIST </a>.
* The hashed value has 256 bits.
*/
public class Passwords {
private static final Random RANDOM = new SecureRandom();
private static final int ITERATIONS = 10000;
private static final int KEY_LENGTH = 256;
/**
* static utility class
*/
private Passwords() { }
/**
* Returns a random salt to be used to hash a password.
*
* @return a 16 bytes random salt
*/
public static byte[] getNextSalt() {
byte[] salt = new byte[16];
RANDOM.nextBytes(salt);
return salt;
}
/**
* Returns a salted and hashed password using the provided hash.<br>
* Note - side effect: the password is destroyed (the char[] is filled with zeros)
*
* @param password the password to be hashed
* @param salt a 16 bytes salt, ideally obtained with the getNextSalt method
*
* @return the hashed password with a pinch of salt
*/
public static byte[] hash(char[] password, byte[] salt) {
PBEKeySpec spec = new PBEKeySpec(password, salt, ITERATIONS, KEY_LENGTH);
Arrays.fill(password, Character.MIN_VALUE);
try {
SecretKeyFactory skf = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
return skf.generateSecret(spec).getEncoded();
} catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
throw new AssertionError("Error while hashing a password: " + e.getMessage(), e);
} finally {
spec.clearPassword();
}
}
/**
* Returns true if the given password and salt match the hashed value, false otherwise.<br>
* Note - side effect: the password is destroyed (the char[] is filled with zeros)
*
* @param password the password to check
* @param salt the salt used to hash the password
* @param expectedHash the expected hashed value of the password
*
* @return true if the given password and salt match the hashed value, false otherwise
*/
public static boolean isExpectedPassword(char[] password, byte[] salt, byte[] expectedHash) {
byte[] pwdHash = hash(password, salt);
Arrays.fill(password, Character.MIN_VALUE);
if (pwdHash.length != expectedHash.length) return false;
for (int i = 0; i < pwdHash.length; i++) {
if (pwdHash[i] != expectedHash[i]) return false;
}
return true;
}
/**
* Generates a random password of a given length, using letters and digits.
*
* @param length the length of the password
*
* @return a random password
*/
public static String generateRandomPassword(int length) {
StringBuilder sb = new StringBuilder(length);
for (int i = 0; i < length; i++) {
int c = RANDOM.nextInt(62);
if (c <= 9) {
sb.append(String.valueOf(c));
} else if (c < 36) {
sb.append((char) ('a' + c - 10));
} else {
sb.append((char) ('A' + c - 36));
}
}
return sb.toString();
}
}
关于生成salt，您的方法是正确的，即使用随机数。对于这种情况，它可以保护您的系统免受可能的字典攻击。现在，针对第二个问题，您可以考虑使用Base64而非UTF-8编码。以下是一个生成哈希值的示例。我正在使用Apache Common Codecs进行base64编码，您也可以选择其他编码。
public byte[] generateSalt() {
SecureRandom random = new SecureRandom();
byte bytes[] = new byte[20];
random.nextBytes(bytes);
return bytes;
}
public String bytetoString(byte[] input) {
return org.apache.commons.codec.binary.Base64.encodeBase64String(input);
}
public byte[] getHashWithSalt(String input, HashingTechqniue technique, byte[] salt) throws NoSuchAlgorithmException {
MessageDigest digest = MessageDigest.getInstance(technique.value);
digest.reset();
digest.update(salt);
byte[] hashedBytes = digest.digest(stringToByte(input));
return hashedBytes;
}
public byte[] stringToByte(String input) {
if (Base64.isBase64(input)) {
return Base64.decodeBase64(input);
} else {
return Base64.encodeBase64(input.getBytes());
}
}
这里是一些额外的参考资料，介绍了密码哈希的标准实践直接来自OWASP
另一个使用SHA-3的版本，我正在使用bouncycastle：
接口：
public interface IPasswords {
/**
* Generates a random salt.
*
* @return a byte array with a 64 byte length salt.
*/
byte[] getSalt64();
/**
* Generates a random salt
*
* @return a byte array with a 32 byte length salt.
*/
byte[] getSalt32();
/**
* Generates a new salt, minimum must be 32 bytes long, 64 bytes even better.
*
* @param size the size of the salt
* @return a random salt.
*/
byte[] getSalt(final int size);
/**
* Generates a new hashed password
*
* @param password to be hashed
* @param salt the randomly generated salt
* @return a hashed password
*/
byte[] hash(final String password, final byte[] salt);
/**
* Expected password
*
* @param password to be verified
* @param salt the generated salt (coming from database)
* @param hash the generated hash (coming from database)
* @return true if password matches, false otherwise
*/
boolean isExpectedPassword(final String password, final byte[] salt, final byte[] hash);
/**
* Generates a random password
*
* @param length desired password length
* @return a random password
*/
String generateRandomPassword(final int length);
}
import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.Validate;
import org.apache.log4j.Logger;
import org.bouncycastle.jcajce.provider.digest.SHA3;
import java.io.Serializable;
import java.io.UnsupportedEncodingException;
import java.security.SecureRandom;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Random;
public final class Passwords implements IPasswords, Serializable {
/*serialVersionUID*/
private static final long serialVersionUID = 8036397974428641579L;
private static final Logger LOGGER = Logger.getLogger(Passwords.class);
private static final Random RANDOM = new SecureRandom();
private static final int DEFAULT_SIZE = 64;
private static final char[] symbols;
static {
final StringBuilder tmp = new StringBuilder();
for (char ch = '0'; ch <= '9'; ++ch) {
tmp.append(ch);
}
for (char ch = 'a'; ch <= 'z'; ++ch) {
tmp.append(ch);
}
symbols = tmp.toString().toCharArray();
}
@Override public byte[] getSalt64() {
return getSalt(DEFAULT_SIZE);
}
@Override public byte[] getSalt32() {
return getSalt(32);
}
@Override public byte[] getSalt(int size) {
final byte[] salt;
if (size < 32) {
final String message = String.format("Size < 32, using default of: %d", DEFAULT_SIZE);
LOGGER.warn(message);
salt = new byte[DEFAULT_SIZE];
} else {
salt = new byte[size];
}
RANDOM.nextBytes(salt);
return salt;
}
@Override public byte[] hash(String password, byte[] salt) {
Validate.notNull(password, "Password must not be null");
Validate.notNull(salt, "Salt must not be null");
try {
final byte[] passwordBytes = password.getBytes("UTF-8");
final byte[] all = ArrayUtils.addAll(passwordBytes, salt);
SHA3.DigestSHA3 md = new SHA3.Digest512();
md.update(all);
return md.digest();
} catch (UnsupportedEncodingException e) {
final String message = String
.format("Caught UnsupportedEncodingException e: <%s>", e.getMessage());
LOGGER.error(message);
}
return new byte[0];
}
@Override public boolean isExpectedPassword(final String password, final byte[] salt, final byte[] hash) {
Validate.notNull(password, "Password must not be null");
Validate.notNull(salt, "Salt must not be null");
Validate.notNull(hash, "Hash must not be null");
try {
final byte[] passwordBytes = password.getBytes("UTF-8");
final byte[] all = ArrayUtils.addAll(passwordBytes, salt);
SHA3.DigestSHA3 md = new SHA3.Digest512();
md.update(all);
final byte[] digest = md.digest();
return Arrays.equals(digest, hash);
}catch(UnsupportedEncodingException e){
final String message =
String.format("Caught UnsupportedEncodingException e: <%s>", e.getMessage());
LOGGER.error(message);
}
return false;
}
@Override public String generateRandomPassword(final int length) {
if (length < 1) {
throw new IllegalArgumentException("length must be greater than 0");
}
final char[] buf = new char[length];
for (int idx = 0; idx < buf.length; ++idx) {
buf[idx] = symbols[RANDOM.nextInt(symbols.length)];
}
return shuffle(new String(buf));
}
private String shuffle(final String input){
final List<Character> characters = new ArrayList<Character>();
for(char c:input.toCharArray()){
characters.add(c);
}
final StringBuilder output = new StringBuilder(input.length());
while(characters.size()!=0){
int randPicker = (int)(Math.random()*characters.size());
output.append(characters.remove(randPicker));
}
return output.toString();
}
}
测试用例：
public class PasswordsTest {
private static final Logger LOGGER = Logger.getLogger(PasswordsTest.class);
@Before
public void setup(){
BasicConfigurator.configure();
}
@Test
public void testGeSalt() throws Exception {
IPasswords passwords = new Passwords();
final byte[] bytes = passwords.getSalt(0);
int arrayLength = bytes.length;
assertThat("Expected length is", arrayLength, is(64));
}
@Test
public void testGeSalt32() throws Exception {
IPasswords passwords = new Passwords();
final byte[] bytes = passwords.getSalt32();
int arrayLength = bytes.length;
assertThat("Expected length is", arrayLength, is(32));
}
@Test
public void testGeSalt64() throws Exception {
IPasswords passwords = new Passwords();
final byte[] bytes = passwords.getSalt64();
int arrayLength = bytes.length;
assertThat("Expected length is", arrayLength, is(64));
}
@Test
public void testHash() throws Exception {
IPasswords passwords = new Passwords();
final byte[] hash = passwords.hash("holacomoestas", passwords.getSalt64());
assertThat("Array is not null", hash, Matchers.notNullValue());
}
@Test
public void testSHA3() throws UnsupportedEncodingException {
SHA3.DigestSHA3 md = new SHA3.Digest256();
md.update("holasa".getBytes("UTF-8"));
final byte[] digest = md.digest();
assertThat("expected digest is:",digest,Matchers.notNullValue());
}
@Test
public void testIsExpectedPasswordIncorrect() throws Exception {
String password = "givemebeer";
IPasswords passwords = new Passwords();
final byte[] salt64 = passwords.getSalt64();
final byte[] hash = passwords.hash(password, salt64);
//The salt and the hash go to database.
final boolean isPasswordCorrect = passwords.isExpectedPassword("jfjdsjfsd", salt64, hash);
assertThat("Password is not correct", isPasswordCorrect, is(false));
}
@Test
public void testIsExpectedPasswordCorrect() throws Exception {
String password = "givemebeer";
IPasswords passwords = new Passwords();
final byte[] salt64 = passwords.getSalt64();
final byte[] hash = passwords.hash(password, salt64);
//The salt and the hash go to database.
final boolean isPasswordCorrect = passwords.isExpectedPassword("givemebeer", salt64, hash);
assertThat("Password is correct", isPasswordCorrect, is(true));
}
@Test
public void testGenerateRandomPassword() throws Exception {
IPasswords passwords = new Passwords();
final String randomPassword = passwords.generateRandomPassword(10);
LOGGER.info(randomPassword);
assertThat("Random password is not null", randomPassword, Matchers.notNullValue());
}
}
pom.xml（仅依赖项）：
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.testng</groupId>
<artifactId>testng</artifactId>
<version>6.1.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.hamcrest</groupId>
<artifactId>hamcrest-all</artifactId>
<version>1.3</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
<dependency>
<groupId>org.bouncycastle</groupId>
<artifactId>bcprov-jdk15on</artifactId>
<version>1.51</version>
<type>jar</type>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.3.2</version>
</dependency>
</dependencies>
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;
import java.util.Base64;
import java.util.Base64.Encoder;
import java.util.Scanner;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
public class Cryptography {
public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeySpecException {
Encoder encoder = Base64.getUrlEncoder().withoutPadding();
System.out.print("Password: ");
String strPassword = new Scanner(System.in).nextLine();
byte[] bSalt = Salt();
String strSalt = encoder.encodeToString(bSalt); // Byte to String
System.out.println("Salt: " + strSalt);
System.out.println("String to be hashed: " + strPassword + strSalt);
String strHash = encoder.encodeToString(Hash(strPassword, bSalt)); // Byte to String
System.out.println("Hashed value (Password + Salt value): " + strHash);
}
private static byte[] Salt() {
SecureRandom random = new SecureRandom();
byte salt[] = new byte[6];
random.nextBytes(salt);
return salt;
}
private static byte[] Hash(String password, byte[] salt) throws NoSuchAlgorithmException, InvalidKeySpecException {
KeySpec spec = new PBEKeySpec(password.toCharArray(), salt, 65536, 128);
SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
byte[] hash = factory.generateSecret(spec).getEncoded();
return hash;
}
}
您可以通过解码strSalt并使用相同的hash方法进行验证：
public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeySpecException {
Encoder encoder = Base64.getUrlEncoder().withoutPadding();
Decoder decoder = Base64.getUrlDecoder();
System.out.print("Password: ");
String strPassword = new Scanner(System.in).nextLine();
String strSalt = "Your Salt String Here";
byte[] bSalt = decoder.decode(strSalt); // String to Byte
System.out.println("Salt: " + strSalt);
System.out.println("String to be hashed: " + strPassword + strSalt);
String strHash = encoder.encodeToString(Hash(strPassword, bSalt)); // Byte to String
System.out.println("Hashed value (Password + Salt value): " + strHash);
}