This greatly reduces the number of possibilities you have to try until you reach the correct string. With that being said, it is generally quite rare to have a situation where you know the hash but not the salt since both are usually stored in the same place.
If you know how the salt is used when hashing the clear text phrase this only makes it easier to brute force.
The number of possibilities you have to check will be going dramatically down, since you only have to check for the phrase without the salt. Still if it is a long phrase with many different characters it will take a lot of time. When password is not salted, and for example function md5 is used, then a potential hacker can go to online databases, and just a lookup there for a right password. When password is salted, then one must brute force it, which is very time consuming. If attacker do not know salt, then in practice it's impossible to hack it at all.
Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Is it possible to crack hash with known salt? If yes how? Ask Question. Asked 6 years, 8 months ago. Active 3 years, 7 months ago. Viewed 70k times. Improve this question. Anders Add a comment. The attacker can then simply do a password reverse lookup by using the hashes from a stolen password database.
The main difference between a hash table attack and a dictionary and brute-force attack is pre-computation. Hash table attacks are fast because the attacker doesn't have to spend any time computing any hashes. The trade-off for the speed gained is the immense amount of space required to host a hash table. Since time and space are limited, the attacker that designs and computes the hash table may want to process the most commonly used passwords first.
Here is where alice and bob could be at a much higher risk if dontpwnme4 is in that common-password list. Large common-password databases are created using frequency analysis across passwords collected from different publicly leaked breaches. The strength of hash tables comes from volume not computation speed and the volume is huge! Each data breach adds to this volume. For a list of companies that have been breached visit the pwned websites list of haveibeenpwned.
There is a balance between making data searchable early and performing sufficient due diligence to establish the legitimacy of the breach. 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. To mitigate the damage that a hash table or a dictionary attack could do, we salt the passwords.
According to OWASP Guidelines , a salt is a value generated by a cryptographically secure function that is added to the input of hash functions to create unique hashes for every input, regardless of the input not being unique. A salt makes a hash function look non-deterministic, which is good as we don't want to reveal duplicate passwords through our hashing. We can salt that password by either appending or prepending the salt to it.
For example: farmM0Of1nd1ngn3m0 or f1nd1ngn3m0farmM0O are valid salted passwords. Once the salt is added, we can then hash it. Let's see this in action:. Hash SHA : ed35c6ebf7ea02fd98ab88d92ccf4e48a4bfccb90aec.
Hash SHA : 07 dbb6edadde4bf1a94a7b3dd26ff3c This demonstrates the importance of using unique salts. Both salted passwords would hash to the same value. But, if we choose another salt for the same password, we get two unique and longer passwords that hash to a different value.
Let's visualize this through an example:. Alice and Bob decide to use both the same password, farmM0O. For Alice, we'll use f1nd1ngn3m0 again as the salt. However, for Bob, we'll use f1nd1ngd0ry as the salt:. Hash SHA : 11 ceb6c1bfbe60a0aa2a2f8c0a0ceed92fea5bfdc8f6. Different users, same password. Different salts, different hashes. If someone looked at the full list of password hashes, no one would be able to tell that Alice and Bob both use the same password.
Each unique salt extends the password farmM0O and transforms it into a unique password. Additionally, when a user changes their password, the service should also generate a new salt. In practice, we store the salt in cleartext along with the hash in our database. We would store the salt f1nd1ngn3m0 , the hash 07 dbb6edadde4bf1a94a7b3dd26ff3c , and the username together so that when the user logs in, we can lookup the username, append the salt to the provided password, hash it, and then verify if the stored hash matches the computed hash.
Now we can see why it is very important that each input is salted with unique random data. When the salt is unique for each hash, we inconvenience the attacker by now having to compute a hash table for each user hash. This creates a big bottleneck for the attacker.
Ideally, we want the salt to be truly random and unpredictable to bring the attacker to a halt. 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. Can you please show me the way of achieving my goal with JTR? Improve this question. Add a comment. Active Oldest Votes.
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