public class BCrypt extends Object
This password hashing system tries to thwart off-line password cracking using a computationally-intensive hashing algorithm, based on Bruce Schneier's Blowfish cipher. The work factor of the algorithm is parameterised, so it can be increased as computers get faster.
Usage is really simple. To hash a password for the first time, call the hashpw method with a random salt, like this:
String pw_hash = BCrypt.hashpw(plain_password, BCrypt.gensalt());
To check whether a plaintext password matches one that has been hashed previously, use the checkpw method:
if (BCrypt.checkpw(candidate_password, stored_hash))
System.out.println("It matches");
else
System.out.println("It does not match");
The gensalt() method takes an optional parameter (log_rounds)
that determines the computational complexity of the hashing:
String strong_salt = BCrypt.gensalt(10)
String stronger_salt = BCrypt.gensalt(12)
The amount of work increases exponentially (2**log_rounds), so each increment is twice as much work. The default log_rounds is 10, and the valid range is 4 to 30.
Limitation of BCrypt is that passwords have a maximum length of 72 bytes after which they will get truncated. Pay attention to the unit "bytes" which will mean your passwords can safely go up to 72 ASCII characters but e.g. only up to 18 when you have UTF-8 characters each taking 4 bytes.
| Constructor and Description |
|---|
BCrypt() |
| Modifier and Type | Method and Description |
|---|---|
static boolean |
checkpw(String plaintext,
String hashed)
Check that a plaintext password matches a previously hashed
one
|
byte[] |
crypt_raw(byte[] password,
byte[] salt,
int log_rounds,
int[] cdata)
Perform the central password hashing step in the
bcrypt scheme
|
static String |
gensalt()
Generate a salt for use with the BCrypt.hashpw() method,
selecting a reasonable default for the number of hashing
rounds to apply
|
static String |
gensalt(int log_rounds)
Generate a salt for use with the BCrypt.hashpw() method
|
static String |
gensalt(int log_rounds,
SecureRandom random)
Generate a salt for use with the BCrypt.hashpw() method
|
static String |
hashpw(String password,
String salt)
Hash a password using the OpenBSD bcrypt scheme
|
public byte[] crypt_raw(byte[] password,
byte[] salt,
int log_rounds,
int[] cdata)
password - the password to hashsalt - the binary salt to hash with the passwordlog_rounds - the binary logarithm of the number
of rounds of hashing to applycdata - the plaintext to encryptpublic static String hashpw(String password, String salt)
password - the password to hashsalt - the salt to hash with (perhaps generated
using BCrypt.gensalt)public static String gensalt(int log_rounds, SecureRandom random)
log_rounds - the log2 of the number of rounds of
hashing to apply - the work factor therefore increases as
2**log_rounds.random - an instance of SecureRandom to usepublic static String gensalt(int log_rounds)
log_rounds - the log2 of the number of rounds of
hashing to apply - the work factor therefore increases as
2**log_rounds.public static String gensalt()
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