Teletype

Teletype machines allowed an easy solution: It was possible to disable the printer while typing on the keyboard. Computing systems that used teletypes would disable the printer when asking for a password. Systems that used Selectric-based terminals, however, could not disable its printer. Instead, the systems would print a mask by repeatedly typing characters over the first several places on the line, making the user’s typing unreadable. When the user typed the password, the letters were typed on top of the mask. Figure 6.5 shows an example of password masking, taken from Boston University’s timesharing system.

Timesharing system designers in the United States did not immediately worry about the remaining attacks on passwords, despite problems with the authentication database. The fifth attack, however, posed a worry at the University of Cambridge, England, where they were developing the Titan timesharing system. Their authentication database also contained all usernames and passwords in the system. The Titan system was regularly copied to a backup tape, and they could not protect those tapes against weak threats within the local computing community.

(Smith 232)

Smith, Richard E. Elementary Information Security, 2nd Edition. Jones & Bartlett Learning, 20150223. VitalBook file.

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