You cannot directly turn a hashed value into the password, but you can work out what the password is if you continually generate hashes from passwords until you find one that matches, a so-called brute-force attack, or similar methods.
The salt value needs to be stored by the site, which means sometimes sites use the same salt for every password. This makes it less effective than if individual salts are used.
Large salts also protect against certain methods of attack on hashes, including rainbow tables or logs of hashed passwords previously broken. Both hashing and salting can be repeated more than once to increase the difficulty in breaking the security.
Cryptographers like their seasonings. There are broadly two versions of pepper. The first is simply a known secret value added to each password, which is only beneficial if it is not known by the attacker.
That means every time a user attempts to log into the site it has to try multiple combinations of the pepper and hashing algorithm to find the right pepper value and match the hash value. Even with a small range in the unknown pepper value, trying all the values can take minutes per login attempt, so is rarely used.
Encryption, like hashing, is a function of cryptography, but the main difference is that encryption is something you can undo, while hashing is not. If you need to access the source text to change it or read it, encryption allows you to secure it but still read it after decrypting it.
Hashing cannot be reversed, which means you can only know what the hash represents by matching it with another hash of what you think is the same information. If a site such as a bank asks you to verify particular characters of your password, rather than enter the whole thing, it is encrypting your password as it must decrypt it and verify individual characters rather than simply match the whole password to a stored hash.
Encrypted passwords are typically used for second-factor verification, rather than as the primary login factor. The numbers represent values zero to nine, with a, b, c, d, e and f representing They are widely used in computing as a human-friendly way of representing binary numbers. Each hexadecimal digit represents four bits or half a byte. Originally designed as a cryptographic hashing algorithm, first published in , MD5 has been shown to have extensive weaknesses, which make it relatively easy to break.
Its bit hash values, which are quite easy to produce, are more commonly used for file verification to make sure that a downloaded file has not been tampered with. It should not be used to secure passwords.
It generates bit hash value that is typically rendered as a digit hexadecimal number. As of , SHA-1 was deemed as no longer secure as the exponential increase in computing power and sophisticated methods meant that it was possible to perform a so-called attack on the hash and produce the source password or text without spending millions on computing resource and time. It was first published in , designed by again by the NSA, and an effective attack has yet to be demonstrated against it.
That means SHA-2 is generally recommended for secure hashing. It was standardised in HMAC is one way, just like hashing. The alternative of encrypting after hashing is useful because it allows the key to be replaced. Users need to enter their password if you change the key with this FaceBook setup, in addition to the salt or scrypt parameters. If you encrypt the hash then you can decrypt and re-encrypt it without requiring the user to enter their password.
If your key is ever leaked But you can't rehash a password without the original. This "Onion" construct can be dangerous and should only be done if you have enough reviewers, it does however add multiple favorable properties compared to simple hashing:.
The first unsalted MD5 can be done by clients or frontend servers. It normalizes charset and length and obfuscates passwords early on without being too CPU intensive.
The salt is read from the user database so it is not present on the client, this is was the first HMAC adds. The crypto service or better HSM defends against brute force as the secret key is not known. In fact this predates NIST recommendations to do exactly this. This peppering is not often done as it requires complicated system setup HSM or process isolation - something Facebook can afford.
Since the pepper step could be compromised by insiders, the data is then passed to scrypt, a function designed to make brute force testing of passwords more expensive. It looks a bit like snake oil overdo but the steps can be reasonable explained. If you compare it with the much weaker glibc-SHA2 Voodoo it is really clean. BTW1: memorable Authenticator are generally a bad thing, such schemes can only reduce the risk of handling them.
Based on a talk I was present at, the following additional info may assist you in understanding the whole process:.
Plain MD5 hashing was the original way of storing the password for the service. This was known to be weak, but short of getting everyone to log in and change their password or to have two or more different password formats in the database, the only way to improve security was to wrap the previous hash in another step. As it is layered it is called 'the onion'. You will notice that they did this by adding a properly salted hash as was recommended at the time.
This allows proactive detection of attacks and mitigation. The scrypt step provides a way to make hashing harder over time. As CPUs get faster, you can increase the hardness and make the total hashing time take around the same time. The last HMAC step is mostly to just make the resulting hashes more uniform for database storage. Is this a good idea for new deployments?
No, but it was done only due to the scale and unique problem that Facebook has. 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. How Facebook hashes passwords Ask Question. Asked 3 years, 8 months ago. Active 3 days ago. Viewed 15k times. This slide shows how they hash passwords: Is it a good idea to do such operations with a raw password? Improve this question. Artegon Artegon 1 1 gold badge 2 2 silver badges 4 4 bronze badges. Why do you think it's security through obscurity? It's the industry best practice for password storage.
MD5 and SHA1 are cryptographically weak given modern computing , but this is also from , so I'm not sure if they are still using those algorithms I'd be surprised. I'm confused about what your question is. Can you restate it? Show 3 more comments. Active Oldest Votes. In one of the comments you wrote: I'm asking if something like it makes sense now in In order you should prefer: Using a binding to the official native optimized implementation of Argon2 Refer to the Argon2 spec's "Recommended parameters" section for how to choose parameters.
The choice between Argon2d, Argon2i, and Argon2id may be up for debate. The current official recommendation is Argon2i for people that don't know which one to choose. Update your software so you can choose 1 Protecting encrypted data using a password and can't use Argon2? Use a binding to a native optimized scrypt implementation. Set the single cost parameter high enough to use a lot of RAM and time. If it seems safe to reduce the time scrypt runs then reconsider.
That also reduces the RAM-based cost. Protecting a few passwords, can't use Argon2, and can tolerate slow responses? Use scrypt with the same cost parameters as 4. If you're trying to protect admin accounts then prioritize using very strong passwords and encryption first.
Protecting many users' account passwords and can't use Argon2? Use a library that uses a binding to native optimized bcrypt.
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