password_char = "char";
Specifies the character to be used to mask user input. If password_char is specified and is not null, that character is displayed in the edit box instead of the characters entered by the user. The use of this attribute has no effect on your application's retrieval of the value entered by the user; it alters only the display of the characters in the edit box.
For an example of using the password_char attribute in an application, see About Requesting a Password (AutoLISP).