Factors in the security of a password system

The security of a password-protected system depends on several factors. The system must, of course, be designed for sound overall security, without which no password protection can have any significance. Early passwords on many systems were limited to a few numbers, or upper-case-letters, only often in prescribed patterns limiting the number of possible passwords. Most passwords today usually have fewer such limits. User input is determined by several limiting factors: allowable inputs (numbers / letters, non-visual codes and/or other keys / device inputs), minimum & maximum of time required for input, availability of cut / delete / paste / copy for input, and error/noise tolerance errors in the password or communications input. Some system administrators also enforce other limitations on passwords, such as compulsory change schedules, safe-password analysis feedback, and compulsory length / composition limits. See computer security and computer insecurity.