/bcrypt-for-delphi

BCrypt implementation for Delphi

Primary LanguagePascalThe UnlicenseUnlicense

Bcrypt for Delphi

Bcrypt is an algorithm designed for hashing passwords, and only passwords; i.e. it is:

  • not a high-speed, generic, hashing algorithm
  • not a key derivation function (see PBDKF2, scrypt)
  • computationally and memory expensive
  • limited to passwords of 55 bytes

It was first described by Niels Provos and David Mazières in 1999 for OpenBSD.

It uses the Blowfish encryption algorithm, but with an "expensive key setup" modification, contained in the function EksBlowfishSetup.

Sample Usage

  • To hash a password:

      hash := TBCrypt.HashPassword('correct battery horse staple'); //using default cost factor

  • To hash a password specifying your own cost factor:

      hash := TBCrypt.HashPassword('correct battery horse staple', 14); //specify cost factor 14

  • To verify a password:

      passwordRehashNeeded: Boolean;
  isPasswordValid := TBCrypt.CheckPassword('correct battery horse stapler', expectedHash, {out}passwordRehashNeeded);

The out parameter passwordRehashNeeded indicates if the stored password hash needs to be upgraded. A hash would need to be upgraded if:

  • the password hash took less than 250 ms to compute
  • the stored hash version (e.g. 2, 2x, 2y) needs to be upgraded (i.e. 2a, soon to be 2b)

By convention BCrypt outputs a hash as string such as:

$2a$12$EA6qjRCeBi8bGgs4rhfn8udEGKmu0ayrZYCEJqf6nNIoytowKFncm

The parts of the string are:

Value Meaning Notes
2a Hash algorithm "2a" = current version of BCrypt, "2" = obsolete version of BCrypt, "1" = MD5
12 cost factor Will iterate for 212=4,096 rounds. (Default is 11)
EA6qjRCeBi8bGgs4rhfn8u Salt 22 base64 encoded characters
dEGKmu0ayrZYCEJqf6nNIoytowKFncm Hashed password 31 base64 encoded characters

Because the cost factor is stored with the hash output, bcrypt hashes are backwards and forwards compatible with changing the number of rounds. It also makes BCrypt extraordinarily convenient in that a random salt is automatically generated and stored for you (you don't have to worry about storing or retrieving it).

Speed Tests

The current (3/21/2015) hard-coded default for cost is 11. This results in 211 = 2,048 rounds during the key setup.

3/14/2015 Intel Core i5-2500 CPU @ 3.50 GHz Delphi XE6 (32-bit, Release)

Cost Iterations Duration
8 256 iterations 22.0 ms
9 512 iterations 43.3 ms
10 1,024 iterations 85.5 ms
11 2,048 iterations 173.3 ms
12 4,096 iterations 345.6 ms
13 8,192 iterations 694.3 ms
14 16,384 iterations 1,390.5 ms
15 32,768 iterations 2,781.4 ms
16 65,536 iterations 5,564.9 ms

At the time of publication (1999), the default cost was 6 for a normal user and 8 for the superuser.

Bcrypt variants

  • $2$ (June 1999)

    The original specification used the prefix $2$.

    This was in contrast to the other algorithm prefixes in the OpenBSD password file, e.g.:

    • $1$: MD5
    • $5$: SHA-256
    • $6$: SHA-512

  • $2a$

    The original specification did not define how to handle non-ASCII character, or how to handle a null terminator.
    The specification was revised to specify that when hashing strings:

    • the string must be UTF-8 encoded
    • the null terminator must be included

  • $2x$, $2y$ (June 2011)

    A bug was discovered in crypt_blowfish, a PHP implementation of BCrypt. It was mis-handling characters with the 8th bit set.

    They suggested that system administrators update their existing password database: replacing $2a$ with $2x$, to indicate that those hashes are bad (and need to use the old broken algorithm).
    They also suggested the idea of having crypt_blowfish emit $2y$ for hashes generated by the fixed algorithm. Nobody else, including canonical OpenBSD, adopted the idea of 2x/2y. This version marker was was limited to crypt_blowfish.

  • $2b$ (February 2014)

    A bug was discovered in the canonical OpenBSD implemenation of bcrypt.

    They were storing the length of their strings in an unsigned char. If a password was longer than 255 characters, it would overflow and wrap at 255. BCrypt was created for OpenBSD. When they have a bug in their library, they decided its ok to bump the version. This means that everyone else needs to follow suit if you want to remain current to "their" specification.

    Bonus Reading: OpenBSD mailing list item "bcrypt version changes" (2/24/2014)

Created by Ian Boyd 5/3/2012

Public Domain
For more information, please refer to http://unlicense.org/

Note: There is now also Scrypt for Delphi.