However, we also explored that hashing alone is not sufficient to mitigate more involved attacks such as rainbow tables. Instead, we want to provide a one-way road to security by hashing passwords. In previous posts to this Authentication Saga, we learned that storing passwords in plaintext must never be an option. You can add credit card information to LastPass to checkout online faster, and even attach important documents. LastPass (Free) Accessible in the Chrome Web Store, LastPass is a free password manager that will auto-login to all your sites and sync all your passwords under one 'master' password. Open Source Password Manager.
![]() Reverse Decision To Remember When Logging In On Apps Free Password ManagerSome cryptographic software is not designed to scale with computing power. Increasing the speed and power of computers can benefit both the engineers trying to build software systems and the attackers trying to exploit them. Motivation Behind bcryptTechnology changes fast. According to USENIX, in 1976, crypt could hash fewer than 4 passwords per second. What is bcrypt?Bcrypt was designed by Niels Provos and David Mazières based on the Blowfish cipher>): b for Blowfish and crypt for the name of the hashing function used by the UNIX password system.Crypt is a great example of failure to adapt to technology changes. Let's learn how bcrypt allows us to create strong password storage systems. Hence, in the design of a cryptographic solution for this problem, we must account for rapidly evolving hardware and constant password length.This attack vector was well understood by cryptographers in the 90s and an algorithm by the name of bcrypt that met these design specifications was presented in 1999 at USENIX. This is particularly important since, through this attack vector, people tend to keep the length of the passwords constant. A fast function would execute faster when running in much more powerful hardware.To mitigate this attack vector, we could create a cryptographic hash function that can be tuned to run slower in newly available hardware that is, the function scales with computing power. This slow key changing is beneficial to password hashing methods such as bcrypt since the extra computational demand helps protect against dictionary and brute force attacks by slowing down the attack.As shown in "Blowfish in practice">), bcrypt is able to mitigate those kinds of attacks by combining the expensive key setup phase of Blowfish with a variable number of iterations to increase the workload and duration of hash calculations. Thus, cryptography that was exponentially more difficult to break as hardware became faster was required in order to hinder the speed benefits that attackers could get from hardware.The Blowfish cipher is a fast block cipher except when changing keys>), the parameters that establish the functional output of a cryptographic algorithm: each new key requires the pre-processing equivalent to encrypting about 4 kilobytes of text>), which is considered very slow compared to other block ciphers. However, 20 years later, a fast computer with optimized software and hardware was capable of hashing 200,000 passwords per second using that function!Inherently, an attacker could then carry out a complete dictionary attack with extreme efficiency. During key setup, the internal state is initialised. "Provos and Mazières, the designers of bcrypt, used the expensive key setup phase of the Blowfish cipher to develop a new key setup algorithm for Blowfish named "eksblowfish", which stands for "expensive key schedule Blowfish."What's "key setup"? According to Ian Howson, a software engineer at NVIDIA: "Most ciphers consist of a key setup phase and an operation phase. This is good for password hashing as it reduces the number of passwords by second an attacker could hash when crafting a dictionary attack. We can dimish any benefits attackers may get from faster hardware by increasing the number of iterations to make bcrypt slower."`bcrypt` was designed for password hashing hence it is a slow algorithm. The aforementioned practice is also known as key stretching.What we are going through this first phase is to promote key strengthening to slow down calculations which in turn also slow down attackers.The magic value is the 192-bit value OrpheanBeholderScryDoubt. In case that the user selected a bad or short password, we stretch that password/key into a longer password/key. Here, the password is used as the primary key. Then, bcrypt spends a lot of time running an expensive key schedule which consists of performing a key derivation where we derive a set of subkeys from a primary key. Key setup only needs to be conducted once for each key that is used"A function called EksBlowfishSetup is setup using the desired cost, the salt, and the password to initialize the state of eksblowfish. Download weather widget for macThis cost is also known as the work factor. This adaptability is what allows us to compensate for increasing computer power, but it comes with an opportunity cost: speed or security? bcrypt Best PracticesThe challenge of security engineers is to decide what cost to set for the function. Its mathematical design gives assurance to cryptographers about its resilience to attacks.Regarding adaptable cost, we could say that bcrypt is an adaptive hash function as we are able to increase the number of iterations performed by the function based on a passed key factor, the cost. The salt space is large enough to mitigate precomputation attacks, such as rainbow tables.The designers of bcrypt believe that the function will hold its strength and value for many years. The prefixes are added to indicate usage of bcrypt and its version.The result of bcrypt achieves core properties of a secure password function as defined by its designers: The output of this phase is the cost and the 128-bit salt value concatenated with the result of the encryption loop.The resulting hash is prefixed with $ 2a$, $ 2y$, or $ 2b$. Analyze with your security team if the computation time is enough to mitigate and slow down attacks.Users may be fine waiting for 1 or 2 seconds as they don't have to consistently authenticate. If the accepted wait time is 1 second, tune the cost of bcrypt for it to run in 1 second on your hardware. Perform UX research to find what are acceptable user wait times for registration and authentication. Increasing the cost factor increases computation time. A migration process is necessary in this case.Check out a cool graph that shows the numbers of transistors on integrated circuit chips from 1971 to 2016."When using `bcrypt`, it's critical to find the right balance between security and usability. However, we need to be careful with this: if we simply increase the work factor of bcrypt in our code, everyone will be locked out. In 2 years, we could increase the cost factor to accommodate any change. Following a modern definition of Moore's Law, the number of transistors per square inch on integrated systems has been doubling approximately every 18 months. Whereas, this delay would frustrate the efforts of an attacker to quickly compute a rainbow table.Being able to tune the cost of bcrypt allow us to scale with hardware optimization.
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