Pritchard, J. A. T., <br/><br/>
Data encryption / 
by John A.T. Pritchard 
 - Manchester :  National Computing Centre,  1980 
 - 1v. (various pagings) ;  30 cm. 
<br/><br/>Includes bibliographical references 
<br/><br/><label>ISBN: </label>0850122538 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Computers--Access control--Passwords