[Morrison & Foerster LLP Letterhead]

                                                                     EXHIBIT 5.1

June 11, 2002

Cylink Corporation
3151 Jay Street
Santa Clara, CA  95054

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  June  11,  2002  (the  "Registration
Statement"),  relating to the registration  under the Securities Act of 1933, as
amended,  of 328,436 shares of the Company's  Common Stock (the  "Shares").  The
Shares are reserved for issuance  pursuant to the Company's  2000 Employee Stock
Purchase 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