Scor­pio News

  

April–June 1988, Volume 2, Issue 2











Page 9 of 35











Notes on CP/M 3 Password Protection

by A.G.H. Sibley

Introduction

The CP/M 3, or CP/M-Plus, operating system for 8080/Z80 machines provides two levels of password protection, namely a disk restriction and a file protection system. Exactly how the passwords are stored in an encrypted form and how: the programmer may access these areas to decode the password, in tlie event of a loss of memory faculties, is explained below.

In order to use password and date time stamping of files,.a’CP/M 3 utility, INITDIR.COM, is run to reorganise the directory area. This creates space in the disk directory for the date/time stamping and passwords but-at the expense of halving the number of directory entries. The area which is created i is known as the Extended File Control Block, XFCB. – Lo

Label XFCB construction

oy ON BR If the directory area on a disk (which has been label stamped) is examined using a suitable utility like DU.COM, then the following should be seen: © .

DISK UTILITY v8.6 Universal Version under CP/M 3.1

Type ? for help Type X to exit

00 00534554 20202020 20434F4D 00000051 *.SET COM. ..Q*
10 02030405 06070000 00000000 00000000 *..... eee eee eeee
20 20544553 54202020 20202020 81440000 * TEST © De.
30 64646464 75757575 12070000 12070000 *dddduuuu........
40 00444154 45202020 20434F4D 00000016 *.DATE COM....
50 08090000 00000000 00000000 O0000000 *... cee ec ec eevee’
60 00444952 20202020 20434F4D 00000072 *.DIR COM...xr*
70 OAOBOCOD OEOF1011 00000000 O0000000 *... cece cece cee e®

This is an OCR’d version of the scanned page and likely contains recognition errors.











Page 9 of 35