EXHIBIT 5.1

September 26, 2001


Ladies and Gentlemen:

         We have examined the Registration  Statement on Form S-8 to be filed by
Cylink  Corporation,   a  California  corporation  (the  "Company"),   with  the
Securities  and Exchange  Commission  on September  26, 2001 (the  "Registration
Statement"),  relating to the registration  under the Securities Act of 1933, as
amended, of 10,276,449 shares of the Company's Common Stock (the "Shares").  The
Shares  are  reserved  for  issuance  pursuant  to the Cylink  Corporation  1994
Flexible  Stock  Incentive  Plan,  the Cylink ATM  Technology  Center 2000 Stock
Option Plan and the Cylink Corporation 2001 Non-Qualified Stock Option Plan . As
counsel to the Company, we have examined the proceedings taken by the Company in
connection with the registration of the Shares.

         It is our opinion  that the Shares,  when issued and sold in the manner
described in the  Registration  Statement  and the related  Prospectus,  will be
legally and validly issued, fully paid and nonassessable.

         We consent to the use of this opinion as an exhibit to the Registration
Statement  and  further  consent  to all  references  to us in the  Registration
Statement and any amendments thereto.


                                                     Very truly yours,

                                                     /s/ Morrison & Foerster LLP
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