261
votes
Accepted
How can I create a password that says "SALT ME!" when hashed?
The output of MD5 is binary: a sequence of 128 bits, commonly encoded as 16 bytes (technically, 16 octets, but let's use the common convention of bytes being octets).
Humans don't read bits or bytes. ...
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178
votes
Accepted
Does anybody not store salts?
Not storing the salt is bad advice.
The main purpose of a salt is that each user password has to be attacked individually.
If you do not store the salt then, as you said, you need to try every ...
- 6,881
127
votes
Does anybody not store salts?
A 'secret' salt is known as a pepper.
From Wikipedia:
A pepper can be added to a password in addition to a salt value. A pepper performs a similar role to a salt, however whereas a salt is ...
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122
votes
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Is it safe/wise to store a salt in the same field as the hashed password?
You should store it in a single field. Do not try to divide it into parts.
I know this might seem a bit unintuitive for people coming from a database background, where the modus operandi is to ...
- 64.2k
106
votes
Is there any real value in hashing/salting passwords?
Users often use the same passwords on multiple sites. Your site might not have any financial data, but what if the same password is used for their bank, or for an online store?
You could argue that ...
- 27.2k
100
votes
Accepted
Secret salts; why do they slow down attacker more than they do me?
This would probably be explained in the auditory lecture that these slides accompany.
My guess is that he's calculating this assuming that users generally enter their correct passwords. You only need ...
- 9,383
81
votes
Convincing my manager to use salts
I'm not sure where you are from. First of all his opinion is against the the considered industry best practice as defined by NIST. Furthermore your manager is dangerously wrong. The more users the ...
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74
votes
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How does the attacker know what algorithm and salt to use in a dictionary attack?
How are plaintext and hashes compared?
During the brute force attack, words from the dictionary are hashed with the correct hash algorithm and salt, and then compared to the hash in the database dump. ...
- 64.2k
70
votes
How often do two users use the same password
The assumption is already wrong. Even if every password was unique, you'd still need salts.
Without salts, the attacker can go through his list of possible passwords just once, compare the hash of ...
- 4,014
61
votes
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Is it safe to check password against the HIBP Pwned Passwords API during account registration?
Have I Been Pwned? allows anyone to download the full database to perform the checks locally.
If that's not an option, using the API is safe, since it uses k-anonimity which allows you to perform the ...
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61
votes
Accepted
How can Freeradius detect if the password provided is right when only the salted hash is stored in the database without the salt
The hash and salt are both in the value column. After Base64 decoding, the first 32 bytes are the hash, and the rest is the salt (in your case, it's the ASCII string seldemer).
50
votes
Accepted
Is there a way to add salted hashing to my user authentication without breaking my former login server
You have conflicting requirements here. The compatibility requirements forces you to keep the old hashes. The security requirements forces you to drop them. You will have to make a choice here about ...
- 64.2k
49
votes
Accepted
Does too long a salt reduce the security of a stored password hash?
As Mike and Gumbo have mentioned in comments, a salt isn't intended to add protection to bad passwords. It's meant to keep the attackers from breaking the whole database at once. The length of the ...
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49
votes
Is there any real value in hashing/salting passwords?
Good question, and I'm glad you asked it. I want people to find this thread when they Google it so they -- hopefully -- won't make the same mistakes that many other companies make.
You shouldn't just ...
- 22.5k
49
votes
Is it safe/wise to store a salt in the same field as the hashed password?
What you're missing is that hashes work on the original data, minus the original string. When you want to validate a string against a hash, you take the supplied string, plus the original hash data (...
- 3,766
47
votes
Accepted
How Does A Random Salt Work?
Is the random salt saved somewhere to be used for each encryption?
Yes
Seems less secure to me if the salt is saved right alongside the hashed password, rather than using some kind of computed ...
- 868
46
votes
Accepted
What are the differences between an encryption seed and salt?
Seed:
Encryption is powered by random numbers, but how do you generate a truly random number? The current millisecond? The number of processor threads in use? You need a starting point. This is ...
- 123k
45
votes
Accepted
Does complexity of salt in password hashing matter?
The important part
The fact that you are generating salts on your own is a red flag. The best way to do this, especially if you have little experience with security, is to use an established library ...
- 64.2k
33
votes
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Password hashing : Using 2 salts
Your second "salt" is a concept which has been described as "peppering". Basically, it works, but has the drawback of implying key management (the "pepper" being really what cryptographers would call ...
- 168k
30
votes
Convincing my manager to use salts
The main purpose of salts is to prevent an attacker from saving work by comparing a single calculated hash with all stored hashes. This problem is independent from whether or not the passwords are ...
- 4,014
29
votes
Accepted
bcrypt no need to store salt?
From a description of bcrypt at Wikipedia:
... The rest of the hash string includes the cost parameter, a 128-bit salt (Radix-64 encoded as 22 characters), and 184 bits of the resulting hash value (...
- 181k
29
votes
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How does a 'rainbow table' hacker obtain password hashes in the first place?
The news is full of examples of leaked databases (this is just the most recent results).
The How:
The vast majority of cases involve unsecured databases/backups (across pretty much all technologies: ...
- 4,061
28
votes
Accepted
Should I remotely store my salt?
It is not a problem if the attacker learns the salts. Salts are not meant to be secret. What is important for a salt is that it is unique for each hashed password instance (i.e. not only a unique salt ...
- 168k
27
votes
Accepted
Find matching phone numbers without actually knowing them
bcrypt would be a somewhat better approach because it is designed to be (programmably) slow.
Using a large enough salt and a reasonable complexityFactor, bcrypt(salt + number, complexityFactor) ...
- 22.5k
26
votes
Convincing my manager to use salts
The "best" counter-argument depends on what you are trying to achieve.
If you just want to be scientifically right, then it suffices to say that salts are not, and never have been, a method to cope ...
- 168k
25
votes
How Does A Random Salt Work?
To verify the hashed password without salt, you compute MD5(privided_password) and compares with the data stored on the database. It makes a trivial search on a hash table to decode lots of your ...
- 50.5k
25
votes
Accepted
Perfectly Robust Hashing Scheme, or Completely Over-Engineered?
This basically looks like something along the lines of PBKDF2 or sha512crypt, only with a bunch of "cryptographic voodoo" applied.
Salts have a very specific cryptographic purpose: to tie an password-...
- 5,726
24
votes
How to crack a password given its hash and its salt using a more efficient method than brute force?
Without any more information, you can not reduce the search space. Since you don't have any prior information about the password, you can't rule out any possible password from the search space.
If ...
- 2,284
24
votes
Is there a way to add salted hashing to my user authentication without breaking my former login server
Is there a secure way to add salt (and pepper) to our authentication
database while maintaining the old application's ability to
authenticate users?
Yes, this can be done. Below are high-level ...
- 922
Only top scored, non community-wiki answers of a minimum length are eligible