http://stackoverflow.com/a/30308723/70465
http://csrc.nist.gov/publications/nistpubs/800-132/nist-sp800-132.pdf
https://www.owasp.org/index.php/Password_Storage_Cheat_Sheet#Work_Factor
http://security.stackexchange.com/a/3993/16485
http://blog.ircmaxell.com/2014/03/why-i-dont-recommend-scrypt.html
http://security.stackexchange.com/a/26253/16485
http://security.stackexchange.com/a/6415/16485
http://wildlyinaccurate.com/bcrypt-choosing-a-work-factor/
https://docs.spring.io/spring-security/site/docs/current/api/org/springframework/security/crypto/bcrypt/BCrypt.html
https://www.openssl.org/docs/man1.1.0/crypto/EVP_BytesToKey.html
http://security.stackexchange.com/a/29139/16485