如何在 Java 中使用 BouncyCastle API 加密和加盐密码？

Question

我对 cryptography 还很陌生，我正在使用BouncyCasetle API 来加密 密码并将其存储在数据库中。对于加密，我正在使用SHA-1 算法，我想对密码加盐以防止它再次受到字典攻击。

任何帮助将不胜感激。

Answer 1

我建议为此使用基于密码的密钥派生函数而不是基本哈希函数。像这样的：

// tuning parameters

// these sizes are relatively arbitrary
int seedBytes = 20;
int hashBytes = 20;

// increase iterations as high as your performance can tolerate
// since this increases computational cost of password guessing
// which should help security
int iterations = 1000;

// to save a new password:

SecureRandom rng = new SecureRandom();
byte[] salt = rng.generateSeed(seedBytes);

Pkcs5S2ParametersGenerator kdf = new Pkcs5S2ParametersGenerator();
kdf.init(passwordToSave.getBytes("UTF-8"), salt, iterations);

byte[] hash =
    ((KeyParameter) kdf.generateDerivedMacParameters(8*hashBytes)).getKey();

// now save salt and hash

// to check a password, given the known previous salt and hash:

kdf = new Pkcs5S2ParametersGenerator();
kdf.init(passwordToCheck.getBytes("UTF-8"), salt, iterations);

byte[] hashToCheck =
    ((KeyParameter) kdf.generateDerivedMacParameters(8*hashBytes)).getKey();

// if the bytes of hashToCheck don't match the bytes of hash
// that means the password is invalid

Answer 2

那么你可以做的是得到一个：

StringBuilder salt=new StringBuilder();
salt.append("MySuperSecretSalt");
MessageDigest md = MessageDigest.getInstance("SHA-256");
String text = "This is text to hash";
salt.append(text);    
md.update(salt.toString().getBytes("UTF-8")); // Change this to "UTF-16" if needed
byte[] digest = md.digest();

您的摘要现在包含您的字符串+盐的哈希值，因此它有助于防止彩虹表。