EXHIBIT 5.01

                               October 26, 2001

VeriSign, Inc.
487 East Middlefield Road
Mountain View, California 94043

Ladies and Gentlemen:

   At your request, we have examined the Registration Statement on Form S-4,
File No. 333-71280 (the "Registration Statement") filed by you with the
Securities and Exchange Commission (the "Commission") on October 10, 2001, as
subsequently amended on or about October 26, 2001, in connection with the
registration under the Securities Act of 1933, as amended, of an aggregate of
34,009,619 shares of your Common Stock (the "Stock") pursuant to the terms of
an Agreement and Plan of Merger dated as of September 23, 2001 (the
"Agreement") by and among VeriSign, Inc., a Delaware corporation ("VeriSign"),
Illuminet Holdings, Inc., a Delaware corporation ("Illuminet"), and Illinois
Acquisition Corporation, a Delaware corporation and wholly owned subsidiary of
VeriSign ("Merger Sub").

   In rendering this opinion, we have examined the following:

   (1) VeriSign's currently effective Certificate of Incorporation, as amended,
       and Merger Sub's currently effective Certificate of Incorporation;

   (2) VeriSign's currently effective Bylaws, as amended, and Merger Sub's
       currently effective Bylaws;

   (3) the Registration Statement, together with the Exhibits filed as a part
       thereof or incorporated by reference therein;

   (4) the prospectus prepared in connection with the Registration Statement,
       together with the Appendices thereto (the "Prospectus");

   (5) the minutes of meetings of VeriSign's Board of Directors, approving the
       Agreement, the issuance of the Stock and the filing of the Registration
       Statement; the unanimous written consent of Merger Sub's Board of
       Directors approving the Agreement and the written consent of Merger
       Sub's sole stockholder approving the Agreement;

   (6) a verification email from VeriSign's transfer agent dated of even date
       herewith verifying the number of VeriSign's issued and outstanding
       shares of capital stock;

   (7) a statement from VeriSign as of the date hereof as to the number of (i)
       outstanding options, warrants and rights to purchase VeriSign Common
       Stock and (ii) any additional shares of VeriSign Common Stock reserved
       for future issuance in connection with VeriSign stock option and
       purchase plans and all other plans, agreements or rights; and

   (8) a Management Certificate addressed to us and dated of even date herewith
       executed by VeriSign and Merger Sub containing certain factual and other
       representations.

   In our examination of documents for purposes of this opinion, we have
assumed, and express no opinion as to, the genuineness of all signatures on
original documents, the authenticity and completeness of all documents
submitted to us as originals, the conformity to originals and completeness of
all documents submitted to us as copies, the legal capacity of all natural
persons executing the same, the lack of any undisclosed termination,
modification, waiver or amendment to any document reviewed by us and the due
authorization, execution and delivery of all documents where due authorization,
execution and delivery are prerequisites to the effectiveness thereof. We have
also assumed that the certificates representing the Stock will be, when issued,
properly signed by authorized officers of VeriSign or their agents.



   As to matters of fact relevant to this opinion, we have relied solely upon
our examination of the documents referred to above and have assumed the current
accuracy and completeness of the information obtained from the documents
referred to above and the representations and warranties made by
representatives of VeriSign to us, including but not limited to those set forth
in the Management Certificate. We have made no independent investigation or
other attempt to verify the accuracy of any of such information or to determine
the existence or non-existence of any other factual matters; however, we are
not aware of any facts that would cause us to believe that the opinion
expressed herein is not accurate.

   We are admitted to practice law in the State of California, and we render
this opinion only with respect to, and express no opinion herein concerning the
application or effect of the laws of any jurisdiction other than, the existing
laws of the United States of America, of the State of California and, with
respect to the validity of corporate action and the requirements for the
issuance of stock, of the State of Delaware.

   In connection with our opinion expressed below, we have assumed that, at or
prior to the time of the delivery of any shares of Stock, the Registration
Statement will have been declared effective under the Securities Act of 1933,
as amended, that the registration will apply to such shares of Stock and will
not have been modified or rescinded and that there will not have occurred any
change in law affecting the validity or enforceability of such shares of Stock.

   Based upon the foregoing, it is our opinion that the shares of Stock to be
issued, sold and delivered by you pursuant to the Registration Statement, when
issued, sold and delivered in the manner and for the consideration stated in
the Registration Statement and the Prospectus, will be 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, if any, in the
Registration Statement, the Prospectus constituting a part thereof and any
amendments thereto. In giving this consent, we do not admit that we are within
the category of persons whose consent is required by the Securities Act of
1933, as amended, or the rules or regulations promulgated thereunder. This
opinion is intended solely for your use in connection with the above issuance
and sale of the Stock subject to the Registration Statement and is not to be
relied upon for any other purpose. We assume no obligation to advise you of any
fact, circumstance, event or change in the law or the facts that may hereafter
be brought to our attention whether or not such occurrence would affect or
modify the opinions expressed herein.

                                          Very truly yours,

                                          /s/ Fenwick & West LLP

                                          FENWICK & WEST LLP