DISCUSSION [NIST SP 800-171 R2]

This requirement applies to single-factor authentication of individuals using passwords as individual or group authenticators, and in a similar manner, when passwords are used as part of multifactor authenticators. The number of changed characters refers to the number of changes required with respect to the total number of positions in the current password. To mitigate certain brute force attacks against passwords, organizations may also consider salting passwords.

FURTHER DISCUSSION

Password complexity means using different types of characters as well as a specified number of characters. This applies to both the creation of new passwords and the modification of existing passwords. Characters to manage complexity include numbers, lowercase and uppercase letters, and symbols. Minimum complexity requirements are left up to the organization to define. Define the lowest level of password complexity required. Define the number of characters that must be changed when an existing password is changed. Enforce these rules for all passwords. Salting passwords adds a string of random characters (salt) to a password prior to hashing. This ensures the randomness of the resulting hash value.

Example

You work with management to define password complexity rules and ensure they are listed in the company’s security policy. You define and enforce a minimum number of characters for each password and ensure that a certain number of characters must be changed when updating passwords [a,b]. Characters include numbers, lowercase and uppercase letters, and symbols [a]. These rules help create hard-to-guess passwords, which help to secure your network.

Potential Considerations

Is a degree of complexity specified for passwords, (e.g., are account passwords a minimum of 12 characters and a mix of upper/lower case, numbers, and special characters), including minimum requirements for each type [a,b,c]?

Is a change of characters required when new passwords are created [d]?

Copyright

Copyright 2020, 2021 Carnegie Mellon University and The Johns Hopkins University Applied Physics Laboratory LLC.

Copyright 2021 Futures, Inc.

This material is based upon work funded and supported by the Department of Defense under Contract No. FA8702-15-D-0002 with Carnegie Mellon University for the operation of the Software Engineering Institute, a federally funded research and development center, and under Contract No. HQ0034-13-D-0003 and Contract No. N00024-13-D-6400 with the Johns Hopkins University Applied Physics Laboratory LLC, a University Affiliated Research Center.

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