Password strength each possible password is equally likely. This seems to suggest that all passwords must contain characters from each of several character classes, perhaps upper and lower case letters, numbers, and non-alphanumeric characters. In fact, such a requirement is a pattern in password choice and can be expected to reduce an attacker's "work factor" (in Claude Shannon's terms). This is a reduction in password "strength". A better requirement would be to require a password NOT to contain any word in an online dictionary, or list of names, or any license plate pattern from any state (in the US) or country (as
Most recent common ancestor Most recent common ancestor In biology and genealogy, the most recent common ancestor (MRCA, also last common ancestor (LCA), or concestor) of any set of organisms is the most recent individual from which all the organisms are directly descended. The term is also used in reference to the ancestry of groups of genes (haplotypes) rather than organisms. The MRCA of a set of individuals can sometimes be determined by referring to an established pedigree. However, in general, it is impossible to identify the exact MRCA of a large set of individuals, but an estimate of the time at which the