17. A method of verifying a previously identified authorized user U k from free typed text, comprising the steps of (1) retrieving an authorized user typing profile from an associated storage device, where said authorized user typing profile is associated with said previously identified authorized user, said authorized user typing profile containing a series of features having associated trial values derived from at least one trial typing sample of alphanumeric data from said previously identified authorized user; (2) receiving a test typing sample of alpha-numeric text from a text input device from a user identified previously as an authorized user, where said alpha-numeric test data is extracted from said user's ongoing text entry at said text input device without sending a notice to said user that said user's text entry is being used to compare to said authorized user profile, (3) extracting a set of test features Z from said received test typing sample, each test feature having a set of non-null numerical values; (4) determining which trial features in said authorized user profile are common with said extracted test features, and comparing said common extracted feature test values to said common authorized user typing profile feature trial values, to derive an authorized user score (5) associating said test typing sample with said previously identified authorized user if said authorized user test score is above a pre-determined value, where said authorized user score is proportional to a conditional probability estimate, P(U k /Z) that the authorized user U k generated the test values associated with said set of extracted features Z.
17. A method of verifying a previously identified authorized user U k from free typed text, comprising the steps of (1) retrieving an authorized user typing profile from an associated storage device, where said authorized user typing profile is associated with said previously identified authorized user, said authorized user typing profile containing a series of features having associated trial values derived from at least one trial typing sample of alphanumeric data from said previously identified authorized user; (2) receiving a test typing sample of alpha-numeric text from a text input device from a user identified previously as an authorized user, where said alpha-numeric test data is extracted from said user's ongoing text entry at said text input device without sending a notice to said user that said user's text entry is being used to compare to said authorized user profile, (3) extracting a set of test features Z from said received test typing sample, each test feature having a set of non-null numerical values; (4) determining which trial features in said authorized user profile are common with said extracted test features, and comparing said common extracted feature test values to said common authorized user typing profile feature trial values, to derive an authorized user score (5) associating said test typing sample with said previously identified authorized user if said authorized user test score is above a pre-determined value, where said authorized user score is proportional to a conditional probability estimate, P(U k /Z) that the authorized user U k generated the test values associated with said set of extracted features Z. 18. The method of claim 17 where said features are extracted from the user's ongoing text entry which comprise correspondence directed to another.