I understand that the addition of a salt provides some protection, because the attacker can no longer just look up the hash value in a rainbow table. However, it is still feasible to write a cracking program that looks up the hash, and then applies the salt to it, since the salt itself is necessarily unencrypted. Thus a salted password is still crackable, though cracking it will take longer. My question is how much longer will it take? Does the salt increase the time-complexity of cracking by a significant order of magnitude? What are the respective time-complexities of cracking an unsalted hash and cracking a salted hash using the same lookup table?
Having salted hashes also makes sense for brute force and dictionary attacks. If the password hashes are not salted, the password cracking software can hash a potential password and check it against all hashes. If the hashes are salted, the attacker needs to calculate the hash for each user. So this increases the work for the attacker by the number of users.
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I don't really understand this part of the question. It is typical and secure to concatenate the password and the salt, hash that, and then store both the hash and the salt. So you store (salt, hash(salt password)). Because the hash function is one way you can not eaasily derive hash(password). To crack this you would have to hash different values for password while using the same salt.
So to crack a password you need to take a very large dictionary of passwords and hash each of them, then compare those hashes to what is in the password database you stole and when you get a match you know the original password.
Hashed passwords that use salts are what most modern authentication systems use. It does not make a password uncrackable but it does slow down the cracking process because it forces a hacker to hash every password that they want to guess.
Because modern password cracking uses salts, if you want to use a dictionary of words to try to crack a password database, it means that you are going to be hashing every one of those words with a salt each time you want to make a guess. So it becomes useful to be able to do hashing fast.
It turns out that modern graphics processing hardware (GPUs or graphics processing units) is very good at hashing and can do it in parallel. Using an off-the-shelf high-end gaming graphics card you can hash passwords thousands of times faster than even the fastest CPU on the market. This has resulted in most competent hackers purchasing GPUs for password cracking or using an online GPU accelerated password cracking cluster.
You now have a good understanding of how passwords are used on services like Gmail, Yahoo, on WordPress websites and most other services that use a password to authenticate you. You also have a reasonable understanding of how to crack passwords.
At Wordfence, we have an 8 GPU cluster that can crack salted MD5 at a rate of 90.6 billion salted MD5 guesses per second. It will take us 1128 seconds or 18 minutes to crack your password if we are guessing every single combination of letter and number 9 characters long. We can do it faster than that if we exclude certain patterns.
It is important to note that your password should be random characters and not made up of patterns like beginning or ending with a number or dictionary words. As soon as you introduce dictionary words and predictable patterns into passwords, they become significantly easier to guess because a password cracker can simply exclude everything that does not match a predictable pattern.
Another useful algorithm is scrypt which is designed to make it difficult to do calculations in parallel. That means that a hacker can no longer use the 2000 cores in their GPU to try to crack your password at the same time. They instead need to make one guess at a time.
That concludes our introduction to hashing and passwords. We have covered the history of password storage, why password hashing is used, what rainbow tables are and how salted passwords defeat a Rainbow Tables attack. We have also discussed how password cracking is done and how hardware like GPUs ASICs and FPGAs can accelerate cracking. We also gave you a brief introduction to algorithms that make it more difficult to crack passwords and a performance architecture that allows the use of a strong hashing algorithm without overloading servers.
Make no mistake about it, disk encryption is a powerful security precaution. Using strong disk encryption means that your data is under your control and only your control. An unauthorized intruder who's able to gain access to that encrypted data but doesn't have proper sign-in credentials (your username and password) or a recovery key is able to see what looks like pure gibberish. And brute-force techniques aren't effective. Even with the assets of the world's most powerful intelligence agencies, it can take years or even centuries to crack that code and decrypt the underlying data.
So the program works. But my problem is, it gets so extremely slow after a certain period. In fact, it actually runs a little faster without multithreading and just using a for loop to iterate through each username/password.
Fortunately, despite choosing the same password, alice and bob chose a password that is not easily found in a dictionary: dontpwnme4. Our friend mike, on the other hand, chose friendship as his password which is a direct entry in the English dictionary. mike is at high risk of being breached through a dictionary attack; the risk for alice and bob is no different. To come up with a password such as dontpwnme4, the attacker could use special dictionaries such as leetspeak to crack the password.
Faster CPUs and GPUs, distributed computations, and weak algorithms are making cracking a password much easier. However, because cracking password hashes these days is more challenging than credential stuffing, it is always a good idea to use MFA (Multi-factor Authentication).
While the attacker may be able to crack one password, cracking all passwords will be unfeasible. Regardless, when a company experiences a data breach, it is impossible to determine which passwords could have been cracked and therefore all passwords must be considered compromised. A request to all users to change their passwords should be issued by the company right away. Upon password change, a new salt should be generated for each user as well.
The security of this scheme does not depend on hiding, splitting, or otherwise obscuring the salt. Simply put, do not mess with the salt. The salt doesn't need to be encrypted, for example. Salts are in place to prevent someone from cracking passwords at large and can be stored in cleartext in the database. However, do not make the salts readily accessible to the public. For that reason, usernames are bad candidates to use as salts.
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Faster calculations mean faster brute-force attacks, for example. Modern hardware in the form of CPUs and GPUs could compute millions, or even billions, of SHA-256 hashes per second against a stolen database. Instead of a fast function, we need a function that is slow at hashing passwords to bring attackers almost to a halt. We also want this function to be adaptive so that we can compensate for future faster hardware by being able to make the function run slower and slower over time.
At Auth0, the integrity and security of our data are one of our highest priorities. We use the industry-grade and battle-tested bcrypt algorithm to securely hash and salt passwords. bcrypt allows building a password security platform that can evolve alongside hardware technology to guard against the threats that the future may bring, such as attackers having the computing power to crack passwords twice as fast. Let's learn about the design and specifications that make bcrypt a cryptographic security standard.
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 is particularly important since, through this attack vector, people tend to keep the length of the passwords constant. Hence, in the design of a cryptographic solution for this problem, we must account for rapidly evolving hardware and constant password length.
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. 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.
If a company ever detects or suspects that a data breach has compromised passwords, even in hash form, it must prompt its users to change their password right away. While hashing and salting prevent a brute-force attack of billions of attempts to be successful, a single password crack is computationally feasible. An attacker may, with tremendous amount of computational power, or by sheer luck, crack a single password, but even then, the process would be most certainly slow due to the characteristics of bcrypt, giving the company and their users precious time to change passwords. 2ff7e9595c
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