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The bcrypt password hashing function requires a larger amount of RAM (but still not tunable separately, i.e. fixed for a given amount of CPU time) and is significantly stronger against such attacks, [13] while the more modern scrypt key derivation function can use arbitrarily large amounts of memory and is therefore more resistant to ASIC and ...
In the context of an HTTP transaction, basic access authentication is a method for an HTTP user agent (e.g. a web browser) to provide a user name and password when making a request. In basic HTTP authentication, a request contains a header field in the form of Authorization: Basic <credentials> , where <credentials> is the Base64 encoding of ID ...
The salt and hash are then stored in the database. To later test if a password a user enters is correct, the same process can be performed on it (appending that user's salt to the password and calculating the resultant hash): if the result does not match the stored hash, it could not have been the correct password that was entered.
When someone requests access, the password they submit is hashed and compared with the stored value. If the database is stolen (an all-too-frequent occurrence [28]), the thief will only have the hash values, not the passwords. Passwords may still be retrieved by an attacker from the hashes, because most people choose passwords in predictable ways.
If the resulting hashes match, then the user is deemed to be authenticated. If the hashes do not match, then the user's authentication attempt is rejected. Since the authentication server has to store the password in clear-text, it is impossible to use different formats for the stored password. If an attacker were to steal the entire database ...
To give her additional assurance that there is no man-in-the-middle attack, Bob creates a proof that he knows the password (or a salted hash thereof), and includes his certificate into this proof. This inclusion is called channel binding, as the lower encryption channel is 'bound' to the higher application channel.
Thus, a program that uses key stretching can use 65,000 rounds of hashes and delay the user for at most one second. Testing a trial password or passphrase typically requires one hash operation. But if key stretching was used, the attacker must compute a strengthened key for each key they test, meaning there are 65,000 hashes to compute per test.
Example of a Key Derivation Function chain as used in the Signal Protocol.The output of one KDF function is the input to the next KDF function in the chain. In cryptography, a key derivation function (KDF) is a cryptographic algorithm that derives one or more secret keys from a secret value such as a master key, a password, or a passphrase using a pseudorandom function (which typically uses a ...