我该如何创建密码？

Question

我想给一些用户提供一百万个密码:

1. 它必须至少有6个字符
2. 它必须有数字和字母

我应该Random在这里使用吗？怎么样？

Answer 1

Apache Commons Lang的RandomStringUtils提供了一些生成随机String的方法,可以用作密码.

以下是8个字符密码创建的一些示例:

// Passwords with only alphabetic characters.
for (int i = 0; i < 8; i++) {
    System.out.println(RandomStringUtils.randomAlphabetic(8));
}
System.out.println("--------");
// Passwords with alphabetic and numeric characters.
for (int i = 0; i < 8; i++) {
    System.out.println(RandomStringUtils.randomAlphanumeric(8));
}

这会产生以下结果:

zXHzaLdG
oDtlFDdf
bqPbXVfq
tzQUWuxU
qBHBRKQP
uBLwSvnt
gzBcTnIm
yTUgXlCc
--------
khDzEFD2
cHz1p6yJ
3loXcBau
F6NJAQr7
PyfN079I
8tJye7bu
phfwpY6y
62q27YRt

当然,您还有一些方法可能会限制密码生成所允许的字符集:

for (int i = 0; i < 8; i++) {
    System.out.println(RandomStringUtils.random(8, "abcDEF123"));
}

将只创建包含字符a,b,c,D,E,F,1,2或3的密码:

D13DD1Eb
cac1Dac2
FE1bD2DE
2ab3Fb3D
213cFEFD
3c2FEDDF
FDbFcc1E
b2cD1c11

Answer 2

RandomStringUtils出于安全原因(即密码)使用Apache时,结合使用SecureRandom源非常重要:

RandomStringUtils.random(6, 0, 0, true, true, null, new SecureRandom());

Answer 3

使用SecureRandom,它提供更随机的密码.

您可以使用以下内容创建单个密码(注意:未经测试的代码).

// put here all characters that are allowed in password
char[] allowedCharacters = {'a','b','c','1','2','3','4'};

SecureRandom random = new SecureRandom();
StringBuffer password = new StringBuffer();

for(int i = 0; i < PASSWORD_LENGTH; i++) {
    password.append(allowedCharacters[ random.nextInt(allowedCharacters.length) ]);
}

请注意,这并不能保证每个密码都包含数字和字符.

Answer 4

这是我写的一段时间:

package com.stackoverflow.does.my.code.for.me;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.ArrayList;
import java.util.List;

public class PasswordUtil {

    /** Minimum password length = 6 */
    public static final int MIN_PASSWORD_LENGTH = 6;
    /** Maximum password length = 8 */
    public static final int MAX_PASSWORD_LENGTH = 8;

    /** Uppercase characters A-Z */
    public static final char[] UPPERS = new char[26];
    /** Lowercase characters a-z */
    public static final char[] LOWERS = new char[26];
    /**
     * Printable non-alphanumeric characters, excluding space.
     */
    public static final char[] SPECIALS = new char[32];
    public static final char[] DIGITS = new char[] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };

    static {
        // Static initializer block for populating arrays
        int U = 'A';
        int l = 'a';
        int d = '0';
        for (int i = 0; i < 26; i++) {
            UPPERS[i] = (char) (U + i);
            LOWERS[i] = (char) (l + i);
            if (i < 10) {
                DIGITS[i] = (char) (d + i);
            }
        }
        int p = 0;
        for (int s = 33; s < 127; s++) {
            char specialChar = (char) 32;

            if (s >= 'a' && s <= 'z')
                s = 'z' + 1; // jump over 'a' to 'z'
            else if (s >= 'A' && s <= 'Z')
                s = 'Z' + 1; // jump over 'A' to 'Z'
            else if (s >= '0' && s <= '9')
                s = '9' + 1; // jump over '0' to '9'

            specialChar = (char) s;
            SPECIALS[p] = specialChar;
            p++;
        }
    }

    public String generatePassword() {
        List<char[]> activeSets = new ArrayList<char[]>(4);
        List<char[]> inactiveSets = new ArrayList<char[]>(4);

        activeSets.add(UPPERS);
        activeSets.add(LOWERS);
        activeSets.add(SPECIALS);
        activeSets.add(DIGITS);

        SecureRandom random = new SecureRandom();

        int passwordLength = 5 + random.nextInt(3);
        StringBuffer password = new StringBuffer(passwordLength + 1);

        for (int p = 0; p <= passwordLength; p++) {
            char[] randomSet = null;
            if (activeSets.size() > 1) {
                int rSet = random.nextInt(activeSets.size());
                randomSet = activeSets.get(rSet);
                inactiveSets.add(randomSet);
                activeSets.remove(rSet);
            } else {
                randomSet = activeSets.get(0);
                inactiveSets.add(randomSet);
                activeSets.clear();
                activeSets.addAll(inactiveSets);
                inactiveSets.clear();
            }
            int rChar = random.nextInt(randomSet.length);
            char randomChar = randomSet[rChar];
            password.append(randomChar);
        }

        return password.toString();
    }
}