Browse Definitions :
Definition

password entropy

Password entropy is a measurement of how unpredictable a password is.

Password entropy is based on the character set used (which is expansible by using lowercase, uppercase, numbers as well as symbols) as well as password length. Password entropy predicts how difficult a given password would be to crack through guessing, brute force cracking, dictionary attacks or other common methods.

Password entropy is usually expressed in terms of bits: A password that is already known has zero bits of entropy; one that would be guessed on the first attempt half the time would have 1 bit of entropy. A password's entropy can be calculated by finding the entropy per character, which is a log base 2 of the number of characters in the character set used, multiplied by the number of characters
in the password itself.

NIST provides the following guidelines for user-selected passwords with 30 bits of entropy:

  • Use a minimum of 8 characters selected from  a 94-character set.
  • Include at least one upper case letter, one lower case letter, one number and one special character.
  • Use a dictionary of common words that users should avoid, like a password blacklist.
  • Don’t use any permutations of your username as your password.

Of course password entropy can't be the only thing considered or passwords would be too long, complex and unmemorable. Best practices involve employing something memorable to the user but not easily guessed by anyone else. Because password length is one of the most important factors affecting password entropy and overall strength, a longer password can be simpler than a shorter one and still be effective.

See also: password strength meter

This was last updated in January 2014

Continue Reading About password entropy

SearchNetworking
  • virtual network functions (VNFs)

    Virtual network functions (VNFs) are virtualized tasks formerly carried out by proprietary, dedicated hardware.

  • network functions virtualization (NFV)

    Network functions virtualization (NFV) is a network architecture model designed to virtualize network services that have ...

  • overlay network

    An overlay network is a virtual or logical network that is created on top of an existing physical network.

SearchSecurity
  • X.509 certificate

    An X.509 certificate is a digital certificate that uses the widely accepted international X.509 public key infrastructure (PKI) ...

  • directory traversal

    Directory traversal is a type of HTTP exploit in which a hacker uses the software on a web server to access data in a directory ...

  • malware

    Malware, or malicious software, is any program or file that is intentionally harmful to a computer, network or server.

SearchCIO
  • security audit

    A security audit is a systematic evaluation of the security of a company's information system by measuring how well it conforms ...

  • chief transformation officer (CTO)

    Chief transformation officer is an executive role, often in the C-suite, that focuses on bringing about change as well as growth ...

  • data latency

    Data latency is the time it takes for data packets to be stored or retrieved. In business intelligence (BI), data latency is how ...

SearchHRSoftware
SearchCustomerExperience
  • implementation

    Implementation is the execution or practice of a plan, a method or any design, idea, model, specification, standard or policy for...

  • first call resolution (FCR)

    First call resolution (FCR) is when customer service agents properly address a customer's needs the first time they call.

  • customer intelligence (CI)

    Customer intelligence (CI) is the process of collecting and analyzing detailed customer data from internal and external sources ...

Close