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1import java.math.BigInteger;
2import java.security.NoSuchAlgorithmException;
3import java.security.SecureRandom;
4import java.security.spec.InvalidKeySpecException;
5
6import javax.crypto.SecretKeyFactory;
7import javax.crypto.spec.PBEKeySpec;
8
9public class SecureHashing {
10	private static final String PBKDF2_ALGORITHM = "PBKDF2WithHmacSHA512";
11	private static final String SECURE_RANDOM_ALGORITHM = "SHA1PRNG";
12	private static final int ITERATIONS = 10000;
13	private static final int HASH_BYTE_SIZE = 64 * 8;
14	private static final int SALT_BYTE_SIZE = 64 * 8;
15	
16	
17	
18	public SecureHashing() {
19		
20	}
21	
22	
23	private String convertHexBytesToString(byte[] array) throws NoSuchAlgorithmException {
24		BigInteger bigInteger = new BigInteger(1, array);
25		String hex = bigInteger.toString(16);
26		
27		int paddingLength = (array.length * 2) - hex.length();
28		if (paddingLength > 0) {
29			return String.format("%0" + paddingLength + "d", 0) + hex;
30		} else {
31			return hex;
32		}
33	}
34	private byte[] convertHexStringToBytes(String hex) throws NoSuchAlgorithmException {
35		byte[] bytes = new byte[hex.length() / 2];
36		
37		for (int i = 0; i < bytes.length; i++) {
38			bytes[i] = (byte) Integer.parseInt(hex.substring(2 * i, 2 * i + 2), 16);
39		}
40		
41		return bytes;
42	}
43	private boolean slowEqualsForBytes(byte[] a, byte[] b) {
44		int diff = a.length ^ b.length;
45		for (int i = 0; i < a.length && i < b.length; i++) {
46			diff |= a[i] ^ b[i];
47		}
48
49		return diff == 0;
50	}
51	private byte[] generateSalt() throws NoSuchAlgorithmException {
52		SecureRandom secureRandom = SecureRandom.getInstance(SECURE_RANDOM_ALGORITHM);
53		
54		byte[] salt = new byte[SALT_BYTE_SIZE];
55		secureRandom.nextBytes(salt);
56		
57		return salt;
58	}
59	private byte[] encode(char[] password, byte[] salt, int iterations, int bytes) throws NoSuchAlgorithmException, InvalidKeySpecException {
60		PBEKeySpec pbeKeySpec = new PBEKeySpec(password, salt, iterations, bytes);
61		SecretKeyFactory secretKey = SecretKeyFactory.getInstance(PBKDF2_ALGORITHM);
62		
63		return secretKey.generateSecret(pbeKeySpec).getEncoded();
64	}
65	
66	
67	
68	
69	private String generateStorngPasswordHash(char[] password) throws NoSuchAlgorithmException, InvalidKeySpecException {
70		byte[] salt = generateSalt();
71		
72		byte[] hash = encode(password, salt, ITERATIONS, HASH_BYTE_SIZE);
73
74		return ITERATIONS + ":" + convertHexBytesToString(salt) + ":" + convertHexBytesToString(hash);
75	}
76	private boolean validatePassword(char[] originalPassword, String storedPassword) throws NoSuchAlgorithmException, InvalidKeySpecException {
77		String[] decodedPassword = storedPassword.split(":");
78		byte[] salt = convertHexStringToBytes(decodedPassword[1]);
79		byte[] hash = convertHexStringToBytes(decodedPassword[2]);
80		
81		byte[] validate = encode(originalPassword, salt, ITERATIONS, HASH_BYTE_SIZE);
82		
83		return slowEqualsForBytes(hash, validate);
84	}
85	
86	
87	
88	public String generateStorngPasswordHash(String password) throws NoSuchAlgorithmException, InvalidKeySpecException {
89		return generateStorngPasswordHash(password.toCharArray());
90	}
91	public boolean validatePassword(String originalPassword, String storedPassword) throws NoSuchAlgorithmException, InvalidKeySpecException {
92		return validatePassword(originalPassword.toCharArray(), storedPassword);
93	}
94	public byte[] createSalt() throws NoSuchAlgorithmException {
95		return generateSalt();
96	}
97	
98}