I need to decrypt this hashed password: e59dc19f2a3a569417fa183696f91604 and have the salt: 4067. Is it possible to recover the password with this information?
You mentioned the word decrypt in your question, so I wanted to just mention firstly that hashes are not a means encryption. Encryption is a two way process of encryption and decryption. It's a way of securing data in transit or stasis.
Hashes are a one way algorithm and cannot be decrypted. However, there are means of finding out what was hashed. If you do some research into Rainbow tables, you'll see that you simply need to build a list of texts (with a salt, in your case) and their corresponding hash.
Hashes and Encryption are like bread and icecream. You can heat up bread and get toast, but you can't cool down toast to get bread. You can head up icecream to get cream, and you can cool it down again to get your icecream back.
No, hash algorithms are one way.
You can hash the original password again and see if the hash result match the previous one.
There is a way to decrypt this, but it is a long and laborious process. It's referred to as "brute-force", which means you would try a large (and by large, I mean significantly large dependent on the length of the password) number of inputs. Since the hash function is a one-way function that produces a non-random result, you will always map an input to the same output. So by using "brute-force", you're literally trying every possible combination and seeing if the hash produced is equal to the hash stored on the system (since you already know the salt). There are tools that do this such as John the Ripper (available on Kali Linux) but again, dependent on your computational power, it can take awhile.
It is impossible to decrypt it. However, you may be able to crack it using the brute force method to find matching passwords in a dictionary.
Best tool to use would be hashcat.
I tried to decrypt a hash with salt, and it works but only with the same encrypt application or method (I mean with the same exact thing, if u encrypt it on a website, or an app you have to decrypt that on the very same place).
I hope that helps
Related
I'm working on a website (PHP + MySQL) that I've got to upgrade. Passwords are stored in the database in MD5, and I'd like it to be something more secure, like SHA-256.
I've already red this question about "converting" password hashes, but I got an other idea, and I'd like to know if it brings a security problem or not.
Currently, the passwords are checked in php by hashing (in MD5) the given password and compare it with the hash stored in database, ie: if(md5($password) == $hash)
Let's assume that I hash all the MD5 hashes in SHA-256. I'd have the sha-256 hash of a md5 hash.
Side note: I know it's not more secure to rehash a hash, that's not the point of my question
When a user wants to connect, I'd just have to change the md5($pass) in hash('sha256', md5($password), false) to make it match the value stored in database (assuming $password is the right one)
It seemed a good idea to me as I don't need to keep track of the md5 hash after conversion, ad this doesn't need me to create any new column in my table. I know that this is not going to give me the SHA-256 hash of the original password stored with md5 hash, but this is not my goal. It's just to change the encryption method. Moreover, brute-forcing it seems inefficient, as it is very unlikely that dictionary would have hashes of words...
Does this way of doing it is flawed?
Simple hashing of passwords is insufficient, it is subject to rainbow tables and is to fast.
Instead in PHP use Safe Password Hashing: password_hash() and password_verify() or a comparable function such as PBKDF2, Bcrypt or script. These function are more secure because of two additions: a repetition count and a random salt. It's all about raising the work factor the attacker must perform.
After all, the point is to have a secure system. Just making it more inconvenient for an attacker is not the answer, there are hacking programs out there to take advantage of poor password security.
So from what I have seen it is impossible to decrypt any hashing algorithm such as MD5 or SHA-1 without brute forcing it or using rainbow tables. This seemed to confuse me on a few aspects of using hashes. These confusing points are:
What would be the point of hashing in the first place if they cant be decrypted?
How would hashed passwords be able to be used in a database?
Also since people say it is like the modulo operation, what, if anything, is preventing multiple inputs to equate to the same hash?
If somebody simply does SHA1 or MD5 on a password, then they get almost no protection.
That's why it's important to understand the right way to handle "password hashing". Please read Our password hashing has no clothes
To answer your questions:
You can verify the user without "decrypting the hash": you simply "hash" the user entered password (along with salt and other parameters) upon login and verify that it matches the expected result that is stored in the database.
See 1 and the Troy Hunt link
People who say it is like a modulo operation are making a bad analogy: they are non-experts on this subject. Anyway, the properties of the "hash" function make it hard to find collisions, and the salt prevents two users with the same password from having the same password "hashes" in the database.
Other resources:
Salted password hashing - Doing it right
Method to Protect Passwords in Databases for Web Applications -- advanced reading: solves other problems with current solutions to protecting passwords. If you wonder why I put "hash" in quotes above, this will explain it.
It's not like a modulo. A hash is reasonably guaranteed to be unique based on the input. If you enter your passwords in a database as hashes, then all you need to do is to hash the password entry and check it against what you have stored in the database. This way, you are not storing readable passwords in the database which are openly visible to others. Normally, you would have a private key, some salt and something unique like a timestamp included in your hashing algorithm to ensure that it cannot be easily spoofed.
This may help you further:
http://searchsqlserver.techtarget.com/definition/hashing
Even if the process of hashing is basically non decryptable, the problem as pointed before is that each hash is nearly unique, so that means using websites like md5decrypt which contains a lot of different words and their encrypted hashes, one may find the password he is looking for.
That is if the password isn't strong enough in the first place. Obviously one shouldn't use the password "password" for instance because it will probably be found in most of the websites like md5decrypt.
What you should do to protect passwords on your website is actually simple. First, don't use old hashes like md5 or sha1. Use at least sha256, and if you've enough sql storage, sha384 or sha512. You should know that most of the online hashes database are only about the most commonly used hashes (let's say md5,sha1,sha256 in most cases). So you should find a hash type that isn't very represented on online database.
Then you should (you have actually to) use salt when encrypt users passwords, that is add some word, letters, whatever, to the password before you encrypt it, then store that salt somewhere so you can still allow people to log in. You could also add a pepper to the salt to make the all thing stronger.
While using the salt, try to find a way that hackers won't think about, for instance double the salt, or triple it, or try different ways to concat the salt and the actual password, etc. You could also make a double encryption with double salt, like sha512(sha384()), which would be almost impossible to find.
But, please, do not store unencrypted passwords !
I was talking to a friend of mine and he stated that to store user passwords in the database, he, and I quote:
Takes a users password
Hashes it with a random salt
Then, he prefixes the result of #2 with the hash type and the salt, joining them with a pipe delimited string. (e.g. SHA1|RANDOMSALT|afde4343....)
Stores result of #3 in the db
He claims that's it readable, as he "can instantly know" what type of hash digest is used.
I don't think I've ever seen this before, but, I'm looking for reasons on why it would be bad aside from the fact than an unauthorized user can instantly know what type of hash is used to encrypt the passwords and the extra space required for storing the field.
My gut reaction is that this approach to working with passwords is silly, as any indication to help an attacker break passwords is a weakness. Any other reasons I should use to convince him that this is a bad idea?
Thanks!
It is a good idea. Everybody does that, including in the /etc/password (/etc/shadow...) file on Unix systems.
Any decent security model will assume that the attacker knows what kind of hash function is used, if only because the hashing system is a piece of software, store on a hard disk. Conversely, believing in the virtue of not announcing which hash function is used is akin to security through obscurity and that's bad.
So do not try to convince your friend that what he is doing is bad. Instead, let him convince you that what he is doing is good.
PS: this is not password encryption, this is password hashing. Hashing is not a kind of encryption.
It's also good practice to store the hash "cost" (number of times the hash has been stretched), even crypt() does that. Possibly, the worst issue is that you first have to query the database (to know the salt, cost, algorithm) and then check against your generated hash, this requires an extra trip to the DB.
Why is this a good practice? Well, if you have user-specific salts, they have to be stored somewhere... Also, you may (in the future) want to escalate the cost (number of times a hash is "re-hashed") of your hashes to keep up with Moore's Law, if you don't know the original cost you wont be able to do anything.
I strongly recommend that you read this blog post about (secure) password hashing.
What is your preferred method/datatype for storing passwords in a database (preferably SQL Server 2005). The way I have been doing it in several of our applications is to first use the .NET encryption libraries and then store them in the database as binary(16). Is this the preferred method or should I be using a different datatype or allocating more space than 16?
I store the salted hash equivalent of the password in the database and never the password itself, then always compare the hash to the generated one of what the user passed in.
It's too dangerous to ever store the literal password data anywhere. This makes recovery impossible, but when someone forgets or loses a password you can run through some checks and create a new password.
THE preferred method: never store passwords in your DB. Only hashes thereof. Add salt to taste.
I do the same thing you've described, except it is stored as a String. I Base64 encode the encrypted binary value. The amount of space to allocate depends on the encryption algorithm/cipher strength.
I think you are doing it right (given that you use a Salt).
store the hash of the salted-password, such as bcrypt(nounce+pwd). You may prefer bcrypt over SHA1 or MD5 because it can be tuned to be CPU-intensive, therefore making a brute force attack way longer.
add a captcha to the login form after a few login errors (to avoid brute-force attacks)
if your application has a "forgot my password" link, make sure it does not send the new password by email, but instead it should send a link to a (secured) page allowing the user to define a new password (possibly only after confirmation of some personal information, such as the user's birth date, for example). Also, if your application allows the user to define a new password, make sure you require the user to confirm the current password.
and obviously, secure the login form (typically with HTTPS) and the servers themselves
With these measures, your user's passwords will be fairly well protected against:
=> offline dictionary attacks
=> live dictionary attacks
=> denial of service attacks
=> all sorts of attacks!
Since the result of a hash function is a series of byte in the range 0 to 255 (or -128 to 127, depending the signed-ness of your 8-bit data type), storing it as a raw binary field makes the most sense, as it is the most compact representation and requires no additional encoding and decoding steps.
Some databases or drivers don't have great support for binary data types, or sometimes developers just aren't familiar enough with them to feel comfortable. In that case, using a binary-to-text encoding like Base-64 or Base-85, and storing the resulting text in a character field is acceptable.
The size of the field necessary is determined by the hash function that you use. MD5 always outputs 16 bytes, SHA-1 always outputs 20 bytes. Once you select a hash function, you are usually stuck with it, as changing requires a reset of all existing passwords. So, using a variable-size field doesn't buy you anything.
Regarding the "best" way to perform the hashing, I've tried to provide many answers to other SO questions on that topic:
Encrypting passwords
Encrypting passwords
Encrypting passwords in .NET
Salt
Salt: Secret or public?
Hash iterations
I use the sha hash of the username, a guid in the web config, and the password, stored as a varchar(40). If they want to brute force / dictionary they'll need to hack the web server for the guid as well. The username breaks creating a rainbow table across the whole database if they do find the password. If a user wants to change their username, I just reset the password at the same time.
System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(
username.ToLower().Trim(),
ConfigurationManager.AppSettings("salt"),
password
);
A simple hash of the password, or even (salt + password) is not generally adequate.
see:
http://www.matasano.com/log/958/enough-with-the-rainbow-tables-what-you-need-to-know-about-secure-password-schemes/
and
http://gom-jabbar.org/articles/2008/12/03/why-you-should-use-bcrypt-to-store-your-passwords
Both recommend the bcrypt algorithms. Free implementations can be found online for most popular languages.
You can use multiple hashes in your database, it just requires a little bit of extra effort. It's well worth it though if you think there's the remotest chance you'll need to support additional formats in the future. I'll often use password entries like
{hashId}${salt}${hashed password}
where "hashId" is just some number I use internally to recognize that, e.g., I'm using SHA1 with a specific hash pattern; "salt" is a base64-encoded random salt; and "hashed password" is a base64-encoded hash. If you need to migrate hashes you can intercept people with an old password format and make them change their password the next time they log in.
As others have mentioned you want to be careful with your hashes since it's easy to do something that's not really secure, e.g., H(salt,password) is far weaker than H(password,salt), but at the same time you want to balance the effort put into this with the value of the site content. I'll often use H(H(password,salt),password).
Finally, the cost of using base64-encoded passwords is modest when compared to the benefits of being able to use various tools that expect text data. Yeah, they should be more flexible, but are you ready to tell your boss that he can't use his favorite third party tool because you want to save a few bytes per record? :-)
Edited to add one other comment: if I suggested deliberately using an algorithm that burned even a 1/10th of a second hashing each password I would be lucky to just be laughed out of my boss's office. (Not so lucky? He would jot something down to discuss at my next annual review.) Burning that time isn't a problem when you have dozens, or even hundreds, of users. If you're pushing 100k users you'll usually have multiple people logging in at the same time. You need something fast and strong, not slow and strong. The "but what about the credit card information?" is disingenuous at best since stored credit card information shouldn't be anywhere near your regular database, and would be encrypted by the application anyway, not individual users.
If you are working with ASP.Net you can use the built in membership API.
It supports many types of storage options, inlcuding; one way hash, two way encryption, md5 + salt. http://www.asp.net/learn/security for more info.
If you dont need anything too fancy, this is great for websites.
If you are not using ASP.Net here is a good link to a few articles from 4guys and codeproject
https://web.archive.org/web/20210519000117/http://aspnet.4guysfromrolla.com/articles/081705-1.aspx
https://web.archive.org/web/20210510025422/http://aspnet.4guysfromrolla.com/articles/103002-1.aspx
http://www.codeproject.com/KB/security/SimpleEncryption.aspx
Since your question is about storage method & size I will address that.
Storage type can be either binary or text representation (base64 is the most common). Binary is smaller but I find working with text easier. If you are doing per user salting (different salt per password) then it is easier to store salt+hash as a single combined string.
The size is hash algorithm dependent. The output of MD5 is always 16 bytes, SHA1 is always 20 bytes. SHA-256 & SHA-512 are 32 & 64 bytes respectively. If you are using text encoding you will need slightly more storage depending on the encoding method. I tend to use Base64 because storage is relatively cheap. Base64 is going to require roughly 33% larger field.
If you have per user salting you will need space for the hash also. Putting it all together 64bit salt + SHA1 hash (160 bit) base64 encoded takes 40 characters so I store it as char(40).
Lastly if you want to do it right you shouldn't be using a single hash but a key derivation function like RBKDF2. SHA1 and MD5 hashes are insanely fast. Even a single threaded application can hash about 30K to 50K passwords per second thats up to 200K passwords per second on quad core machine. GPUs can hash 100x to 1000x as many passwords per second.With speeds like that brute force attacking becomes an acceptable intrusion method. RBKDF2 allows you to specify the number of iterations to fine tune how "slow" your hashing is. The point isn' to bring the system to its knees but to pick a number of iterations so that you cap upper limit on hash throughput (say 500 hashes per second). A future proof method would be to include the number of iterations in the password field (iterations + salt + hash). This would allow increasing iterations in the future to keep pace with more powerful processors. To be even more flexible use varchar to allow potentially larger/alternative hashes in the future.
The .Net implementation is RFC2892DeriveBytes
http://msdn.microsoft.com/en-us/library/system.security.cryptography.rfc2898derivebytes.aspx
What is a good, simple encryption scheme for protecting passwords in a database? I don't necessarily need anything that's hyper-secure nor do I need anything that's lightning fast, but those things would be nice. Primarily, I just want something that's easy to implement without being terribly slow or insecure.
As mk says, SHA1 or MD5 are the standard ones, along with SHA2.
Update: As processors have gotten faster over the years, hashes have gotten more brute-forceable. It's now recommended you use bcrypt.
Another update: bcrypt is still probably good, but if I was writing a new system today I would use scrypt.
What you want is more generally called a cryptographic hash function. Cryptographic hashes are designed to be one-way (given the resulting hash, you shouldn't be able to derive the original input). Also, the likelihood of two arbitrary strings having the same hash (known as a hash collision) should be low (ideally 1/number of hash values).
Unfortunately, just because your passwords are hashed doesn't free you from having to try really hard to keep the hashed versions safe. Far too many people will use weak passwords that would be vulnerable to an off-line brute-force attack.
Edit - several people have also already pointed out the importance of using a salt. A salt is a constant value that you mix in with the input before using the hash function. Having a unique salt prevents off-line attackers from using pre-computed tables of common passwords (rainbow tables) to brute-force your passwords even faster.
MD5 or SHA1 + salt.
If you use MD5 or SHA1 use a salt to avoid rainbow table hacks.
In C# this is easy:
MD5CryptoServiceProvider hasher = new MD5CryptoServiceProvider();
string addSalt = string.Concat( "ummm salty ", password );
byte[] hash = hasher.ComputeHash( Encoding.Unicode.GetBytes( addSalt ) );
Easy: BCrypt.
Use the SHA one way hashing algorithm along with a unique salt. It is the main algorithm I use for storing my passwords in the database.
If you're using SQL Server, there's the HashBytes function:
http://msdn.microsoft.com/en-us/library/ms174415.aspx
I second the vote for MD5 or SHA with a salt. Any of the major web development languages have functions built-in for computing the hash (in PHP, for example, the mcrypt package contains the necessary functions).
You need to be using an uni-directional hash algorithm like SHA-1 suggested above with a salt. I would suggest this site for more information. It includes some sample code / implementation.
http://www.obviex.com/samples/hash.aspx
The key to better security, I think, is to use dynamic salts. This means that you generate a random string for each new user and use that string to salt the hash. Of course, you need to store this salt in the database to be able to verify the password later (I don't encrypt it in any way).
For a non-reversible encryption I would most definitely go with SHA256 or SHA1. MD5 has quite a lot of collisions now and a lot of effort has been put into breaking it, so not a good one to use.
If you want to future-proof your solution, I'd recommend SHA256 or SHA512. Cryptographic geekworld is getting the jitters about MD5 and, to a slightly lesser extent, SHA1.
Or, if you can, wait for SHA-3