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Systems that use passwords for authentication must have some way to check any password entered to gain access. If the valid passwords are simply stored in a system file or database, an attacker who gains sufficient access to the system will obtain all user passwords, giving the attacker access to all accounts on the attacked system and possibly other systems where users employ the same or ...
The above calculations of the Diceware algorithm's entropy assume that, as recommended by Diceware's author, each word is separated by a space. If, instead, words are simply concatenated, the calculated entropy is slightly reduced due to redundancy; for example, the three-word Diceware phrases "in put clammy" and "input clam my" become ...
The entropy of XKCD-style passwords is reduced if users, by habit, attempt to make grammatical sentence fragments out of the four words and if the attackers take this into account. Tools for password cracking use dictionary attacks, and the dictionary is an observation of cultural habits (common words and spellings).
However, even if attempt[0] is not the user's actual password, it will be accepted as if it were, because the system can only check passwords by computing the hash of the password entered and comparing it to the hash stored in the file. Thus, each match cracks a user password, and the chance of a match rises with the number of passwords in the ...
Or in another way; it raises minimum-entropy value of the password set. At the same time it excludes only low-entropy sets (e.g. all lower or all upper case) so the maximum-entropy value passwords are unaffected. The overall result is to force an increase in the median/mean entropy of the password pool.
PBKDF2 is for generating an encryption key from a password, and not necessarily for password authentication. PBKDF2 can be used for both if the number of output bits is less than or equal to the internal hashing algorithm used in PBKDF2, which is usually SHA-2 (up to 512 bits), or used as an encryption key to encrypt static data.
A main encryption/decryption key is derived from user's password by PBKDF2 function. [2] Particular data binary large objects can be encrypted in a way that salt is added and/or an external user-prompted password (aka "Strong Key Protection") is required. The use of a salt is a per-implementation option – i.e. under the control of the ...
The easier a password is for the owner to remember generally means it will be easier for an attacker to guess. [12] However, passwords that are difficult to remember may also reduce the security of a system because (a) users might need to write down or electronically store the password, (b) users will need frequent password resets and (c) users are more likely to re-use the same password ...