A java convenience wrapper for low level hashing functionality
Dependencies:
- (maven) javax.validation:validation-api:2.0.1.Final licence: http://www.apache.org/licenses/LICENSE-2.0
Currently there are two hashing functions available: SHA-256 and PBKDF2-with-HMAC-SHA-256. SHA-256 might be used for any large data that does not need to be stored securely. PBKDF2-with-HMAC-SHA-256 should be used for storing secured hashes eg. of passwords in a database. This is a quite reasonable security directive (but as always: nothing ever is 100% secure).
To generate a SHA-256 hash use:
SHA256Hash hash = SHA256HashBuilder.buildHash("Hello World");
byte[] raw = hash.getHash();
assert hash.getBuilder().getClass() == SHA256.class;
To generate a SHA-256 hash of large data use:
SHA256HashBuilder b = new SHA256HashBuilder();
b.update("Hello");
b.update(" World");
SHA256Hash hash = b.hash();
b.reset();
SHA256Hash hash2 = b.hash("Hello World");
assert hash.equals(hash2);
To generate a PBKDF2-with-HMAC-SHA-256 hash use:
PBKDF2WithHmacSHA256HashBuilder b = new PBKDF2WithHmacSHA256HashBuilder(
SecureHashBuilder.buildSalt( 64 ), /* the salt to vary the hash with. here this salt is securely randomly generated */
500000 /* the iterations to repeatedly compute the hash to harden against brute-force-dehashing */
);
PBKDF2WithHmacSHA256Hash record = b.hash( "my very secure password" );
// save record.getRaw(), record.getSalt() and record.getIterations() to database
// recompute the database record from time to time when user logs in with a different salt to protect against data breaches
// also increase the iterations slightly to keep up with increasing hardware capabilities
To check a second PBKDF2-with-HMAC-SHA-256 hash against a first one (eg for user login) use:
PBKDF2WithHmacSHA256HashBuilder b = new PBKDF2WithHmacSHA256Hash( saltFromDatabase, iterationsFromDatabase );
PBKDF2WithHmacSHA256Hash testHash = b.hash( "password user tries to login with" );
if ( testHash.equals( rawHashFromDatabase ) ) {
// login correct
} else {
// deny access
}
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