A client program (over which I have no control) is authenticating by sending me a password, hashed as SHA1(password).
I'm reluctant to store the password hashed using only SHA1 in my database, so I'm proposing to store passwords in the database hashed as SHA256(SHA1(password)) (where the password is hashed over multiple iterations using PBKDF-2 or something similar).
My question is: is there anything insecure about the inner-most hash using SHA1 in this scenario? I realise that the probability of collisions will be increased, but since this is just for storing passwords in the database I don't think I need to be concerned about that. Is there anything else that I'm missing?
Consider adding a salt which is unique-per-row before doing the final encryption. Example:
Lets say that you receive W6ph5Mm5Pz8GgiULbPgzG37mj9g= (a SHA1'd encryption of "password"). That is associated with a User, who should have a unique key, such as a UserID and/or UserName.
My suggestion - to avoid collision - would be to do a conversion of the Bytes to a Base64String (in C# this would be Convert.ToBase64String( byteVariable ) - then concatenate onto the string the user's unique-ID (making the new string something like:
W6ph5Mm5Pz8GgiULbPgzG37mj9g=+103 (where I added +103 to reflect the user's ID) - then apply your SHA256 algorithm. This will produce: mNXRjWsKJ7V+BHbAuwJJ7neGT+V1IrLQSQXmb4Vv1X8= - which you can store in your database. A SHA256 hash - which eliminates the collisions from the less-safe SHA1 algorithm.
And - since you are using 1-way encryption - when you go to check whether the password is valid in the future, you simply append the user's ID again before checking.
If the client always sends you the same password, simply SHA1 hashed, then the SHA1 hash output is the password, to all intents and purposes. Treat it and store it the same way you would any other password, such as by using PBKDF2, SCrypt, or BCrypt.
Related
I have a key to be decrypted shown here dc6f0dbebfc5747330deeedfbd8475568a740d0a. The following key has salt value prefixed before the key. The salt value is 80808080. How can i decrypt this.
Hashes are not meant to be broken but you can use a tool like this to crack it (If you're lucky). This hash is for the string 'azerty'
Hashes are not decrypted. In their regular usage as password hashes, you can validate an entered password using the hash but you can't find the password given the hash, because the hash function isn't reversible. The exception is brute force password cracking which works for sufficiently simple passwords only.
I'm reversing an app but I'm not very expert of the AES algorithm.
The application gives the user the opportunity to make an offline login.
The user is asked to provide his username and password
This is the function that is used to store the info of the user
public void EncryptLoginInfo(string username, byte[] secretShared, byte[] salt)
{
byte[] random = calc.GenerateRandomBytes();
byte[] array = aes.Encrypt(secretShared, random);
OfflineLogin loginInfo = new OfflineLogin()
{
Username = username,
SecretShared = array,
Iv = random,
Salt = salt
};
this._userCredentials.StoreOfflineLoginData(username, loginInfo);
}
And this are the info that are stored inside an internal config file of the app. In the example below, the password passed to the encryptLoginInfo is 123
Username: not_important
SecretShared: 4KVrjy1cQVWYpWF7aolpMS0HzhKyFf+9VXauQrXoXVUbf0bGXIDOLDJuSVhYoFo2
Iv:yil4nn02IoKsOnX5KXVsDg==
Salt: 5kJio2VQEqjomHRdQMqRVJ0zkBsmqi8K3NypC2VWJk4
If the user want to make an offline login, he is asked to provide username and his password.
Question: Is this algo safe? If an attacker is able to obtain SecretShared+Iv+Salt is he able to recover the password of the user (that in this specific example is 123)
This is the decrypt function
public void DencryptLoginInfo(OfflineLogin loginInfo)
{
byte[] array = aes.Decrypt(loginInfo.SecretShared, loginInfo.Iv);
loginInfo.SecretShared = array;
loginInfo.Iv = (byte[]) null;
}
Are you able to spot any security issues in this implementation? The algo used should be AES-256.. Are you able to implement a POC in python to decrypt the PASSWORD given SecretShared+Iv+Salt?
According to your comment, your goal is to authenticate the user. For that we use password base key derivation functions on the password. Often people refer to this as "hashing passwords", which is unfortunate terminology because "hashing" can mean anything. But the main point is that we do not encrypt passwords, instead we send them through a one-way function that is designed to be slow. The slow speed deters brute force attacks.
You do not need an IV to do this. Instead, your app should be deriving a salt and and using a password based key derivation function (sometimes referred to as a "password hashing" algorithm: you will have to excuse that the industry has made a mess out of the terminology on this topic). You can find guidance on this all over the web. But I suggest you have a read of point 4 in Top 10 Developer Crypto Mistakes to see common pitfalls in implementing this.
Don't use openssl to convert a password into a key (or password hash)! The algorithm in openssl is weak. Openssl's EVP_BytesToKey() fails to meet the requirements of slow speed, meaning that it is easy to brute force your key from your password.
The proper solution to this problem is to use an algorithm such as bcrypt or pbkdf2 (Java implementations can be found without much effort) to derive a "hash" from the password. You then verify that the user typed in the password correctly by re-doing the same computation with the user entered password and the salt that was stored for this password. If they match, access is granted, otherwise access is denied.
Note that if this app interacts with a server, normally you do password verification on the server side. If your app does not interact with a server, then you may have a good reason to do it on the device. I don't know what your app does, so I cannot tell you what is right or wrong for you.
A great reference for doing this properly is How to Safely Store Your Users' Passwords in 2016 .
I'm building an application in which a password is used on the client side to encrypt a private key of a elliptic curve key pair. Then the password is bcrypted and sent to the server (along with the encrypted private key) and the public key.
Originally, I was using pbkdf2 to hash the password before encrypting the private key, but since I'm also bcrypting the password, could I use the bcrypted one instead?
According to https://medium.com/#mpreziuso/password-hashing-pbkdf2-scrypt-bcrypt-1ef4bb9c19b3#.sj4jcbynx the answer is not only yes, but bcrypt is even better as it's more GPU-ASIC resilient. Anything I'm missing?
You should not be using the bcrypt hash output as an encryption key; it is not meant to be key material:
BCrypt is not a key-derivation function
BCrypt it is a password storage function
You have an elliptic curve private key that you want to encrypt using a user's password. Of course you don't want to use the password directly - you want to use the password to derive an encryption key. For that you can use:
PBKDF2
scrypt
These are both key-derivation functions (e.g. password-based key derivation function). Their purpose is to generate an encryption key given a password. They are designed to be "hard".
You feed both these algorithms:
a password
cost parameters
salt
desired number of bytes (e.g. 32 ==> 32 bytes ==> 256 bits)
and it returns you a 256-bit key you can use as an encryption key to AES-256.
You then want to backup the user's key
I gather that you then want to:
store the encrypted elliptic curve private key on your server
store a hash of their password on your server
And your question was: since you already ran their password through "a hashing funtion" can't you just use that hash as their stored password?
No! That hash is also the encryption key protecting their private key. You don't want that private key transmitted anywhere. You don't want it existing anywhere. That 32-byte encryption key should be wiped from memory as soon as you're done with it.
What you should do, if you also wish to store a hash of the user's password is use an algorithm that is typically used for password storage:
pbkdf2 (a key-derivation function abused into password storage)
bcrypt (better than pbkdf2)
scrypt (a key-derivation function abused into password storage; better than bcrypt)
argon2 (better than scrypt)
Update: Argon2/Argon2i/Argon2d/Argon2id is weaker than bcrypt for password authentication (read more)
You should separately run the user's password through one of these password storage algorithms. If you have access to bcrypt; use that over pbkdf2. If you have scrypt, use that for both:
derivation of an encryption key
hashing of the password
The security of your system comes from (in addition to the secrecy of the password), the computational distance between the user's password and the encryption key protecting their private key:
"hunter2" --PBKDF2--> Key material
"hunter2" ---------bcrypt-------> Key material
"hunter2" ----------------scrypt----------> Key material
You want as much distance between the password and the key.
Not-recommended cheat
If you're really desperate to save CPU cycles (and avoid computing scrypt twice), you technically could take:
Key Material ---SHA2---> "hashed password"
And call the hash of the encryption key your "hashed password" and store that. Computation of a single SHA2 is negligible. This is acceptable because the only way an attacker can use this is by trying to guess every possible 256-bit encryption key - which is the problem they can't solve in the first place. There's no way to bruteforce a 256-bit key. And if they were to try to brute-force it, the extra hashed version doesn't help them, as they could just test their attempt by trying to decrypt the private key.
But it's much less desirable because you're storing (a transformed) version of the encryption key. You want that key (and any transformed versions of it) stored as little as possible.
To sum up
generate EC key pair
encryptionKey = scryptDeriveBytes(password, salt, cost, 32)
encryptedPrivateKey = AES256(privateKey, encryptionKey)
passwordHash = scryptHashPassword(password, salt, cost)
and upload
encryptedPrivateKey
passwordhash
An old version of an application has some passwords stored in the clear in its database. I have written an updated version that encrypts the passwords when new entries are made, but I don't have direct access to the database to manually encrypt the entries that already exist. When the update goes live, it will try to decrypt the plaintext passwords, and crash.
Short of doing something drastic like deleting all the existing data, the only other approach I can think of is this (wrapper pseudocode called when the password data is used.):
# data refers to the password data, either encrypted or plain
if data length < AES.block_size:
# (Shorter than initialization vector, definitely not encrypted.)
open database and replace password entry with encrypt(data)
login(username, data)
else:
try: # try plaintext first
login(username, data)
except AuthenticationError:
login(username, decrypt(data))
else: #plain text worked, encrypt data for future use.
open database and replace password entry with encrypt(data)
It seems a shame to keep this code around to solve a problem that goes away after it runs once. Is there any other approach that might work to ensure the passwords are encrypted and only decrypt the ones that need it?
In this scenario I do one of the following, depending on the client and the system involved:
Set up the encrypted password code, delete all existing passwords, and make everyone enter a new password. I prefer this because the passwords were plain and over time may have been seen or shared.
Run a one-time script to encrypt every password in the system. This way there is never a mix.
Have newer encrypted passwords prefixed with the encryption method, e.g. "SHA1:". You run the risk of someone having that same text as the start of their password, but it is unlikely.
I've developed a website that uses ASP.NET membership. Based on comments from previous sites, I decided to encrypt passwords so they could be recovered for users who forgot them.
However, the new site (which now has over 500 registered users) has brought me some criticism that the industry standard is really to hash passwords.
However, after a fairly extensive search, I have been unable to find anything about how to convert existing users' passwords from encrypted to hashed.
I know I can change the web.config file, and new users' passwords will use the new format. But it does nothing to update the existing users.
Note: I previously asked a similar question but mostly just got a debate about which is better, encrypted or hashed. I'm past that discussion but I've been unable to find a way to convert them without losing the hundreds of users already registered.
it seems you already know how to decrypt the passwords and change the web.config file, but you're stuck with how to implement the rest of the process.
using ILSpy, here's how to generate the salt for each user:
byte[] array = new byte[16];
new RNGCryptoServiceProvider().GetBytes(array);
return Convert.ToBase64String(array);
once you have the salt, here's how to generate the password:
byte[] bytes = Encoding.Unicode.GetBytes(pass);
byte[] array = Convert.FromBase64String(salt);
byte[] array2 = new byte[array.Length + bytes.Length];
Buffer.BlockCopy(array, 0, array2, 0, array.Length);
Buffer.BlockCopy(bytes, 0, array2, array.Length, bytes.Length);
using (SHA1CryptoServiceProvider sha1 = new SHA1CryptoServiceProvider()) {
return Convert.ToBase64String(sha1.ComputeHash(array2));
}
where pass is the plain-text password you calculated, and salt is the string calculated in the first code snippet above. the default algorithm is SHA1, if you're wondering why it's being used.
since this is a one-time process, i would write a HTTP handler to manually update the database during a short, scheduled maintenance period - hopefully you have that luxury. (obviously make a backup and test first). you need to update the following fields in the aspnet_Membership table:
Password - calculated above
PasswordFormat - 1
PasswordSalt - calculated above
never had to do anything like this, but hopefully that will get you started :)
IMHO, Greg's response (and the associated comments) on your previous question (Changing passwordFormat from Encrypted to Hashed) is the way to go. Essentially, you want to:
Add a hashed membership provider
Loop through all of the encrypted password users,
For each one decrypt the password, create the hash, store it, delete the encrypted version from the database, and move on.
When you are done, all of the encrypted password users should be converted to hashed.
Maybe I'm missing something here, but it should be pretty simple. Create a process to decrypt the password, then salt accordingly and store the hash of the salt + user's decrypted password in the database. Obviously you don't want to be hashing the user's encrypted password. Don't forget to store the salt too.