<PAGE>

        THE SECURITY REPRESENTED HEREBY HAS NOT BEEN REGISTERED UNDER
        THE SECURITIES ACT OF 1933, AS AMENDED (TOGETHER WITH THE
        RULES AND REGULATIONS PROMULGATED THEREUNDER, COLLECTIVELY,
        THE "SECURITIES ACT"), OR UNDER THE SECURITIES LAWS OF ANY
        STATE. THE SECURITY MAY NOT BE SOLD, TRANSFERRED OR OTHERWISE
        DISPOSED OF UNLESS THE SAME IS REGISTERED AND QUALIFIED IN
        ACCORDANCE WITH THE SECURITIES ACT AND ANY APPLICABLE STATE
        SECURITIES LAWS, OR SOLD PURSUANT TO APPLICABLE STATE
        SECURITIES LAWS, OR SOLD PURSUANT TO AN APPLICABLE EXEMPTION
        FROM REGISTRATION UNDER THE SECURITIES ACT.


                      7% CONVERTIBLE SUBORDINATED DEBENTURE


Debenture No. ___
                                                               $_____________.00
_________, 2000


         Sento Corporation, a Utah corporation (the "COMPANY"), hereby promises
to pay to the order of _____________________ ("PURCHASER") or its registered
assignee (Purchaser or such registered assignee being referred to herein as
"HOLDER") the principal amount of $___________.00 together with interest thereon
calculated from the date hereof in accordance with the provisions of this
debenture (this "DEBENTURE").

         This Debenture is issued pursuant to the Subscription Agreement, dated
as of February 1, 2000 (the "SUBSCRIPTION AGREEMENT"), between the Company and
Purchaser. The Subscription Agreement contains terms governing the rights of
Holder, and all provisions of the Subscription Agreement relating to this
Debenture are hereby incorporated herein in full by reference. This Debenture is
issued as a part of a series of 7% Convertible Subordinated Debentures pursuant
to that certain Private Placement Memorandum, dated January 31, 2000, of the
Company (such debentures being collectively, the "DEBENTURES"). Certain defined
terms used herein are defined in Section 9 below. Unless otherwise indicated
herein, capitalized terms used in this Debenture have the same meanings set
forth in the Subscription Agreement.

         1.   PAYMENT OF INTEREST. Interest will accrue at the rate of seven
percent (7%) per annum (the "INTEREST RATE") on the unpaid principal amount
of the Debenture outstanding from time to time until the first to occur of
the following dates (the "EXPIRATION DATE"): (i) the Conversion Date (as
defined in Section 4 below), (ii) the Redemption Date (as defined in Section
5 below) or (iii) the third anniversary of the Closing Date (as defined in
Section 9 below). Interest will be payable, in arrears, first on June 30,
2000 (with respect to the interest accrued from the date hereof to June 30,
2000) and thereafter semi-annually on the 30th of June and the 31st of
December, or the first business day thereafter, of each year until the
Expiration Date. If, on the first anniversary of the Closing Date (or the
first business day after such anniversary), the Market Price (as defined in
Section 9 below) of the Common Stock (as defined in Section 9 below) is less
than $7.50 per share, the Interest Rate shall increase to 8% from and after
that

<PAGE>

date. Interest will be payable to the person in whose name the Debenture is
registered at the close of business on the 15th day or next subsequent business
day of the month preceding the month in which the payment is made (except with
respect to accrued but unpaid interest on any Conversion Date or Redemption Date
in which case the identity of the Person or Persons entitled to payment of such
interest shall be determined in accordance with Section 4 or 5, respectively).
Interest will be computed on an actual/actual basis.

         2.   SUBORDINATION. The indebtedness evidenced by this Debenture is
an unsecured obligation of the Company and is hereby expressly subordinated,
to the extent and in the manner hereinafter set forth, in right of payment to
the prior payment in full of all the Company's Senior Indebtedness, as
hereinafter defined.

              (a)  SENIOR INDEBTEDNESS. As used in this Debenture, the term
"SENIOR INDEBTEDNESS" shall mean the principal of and unpaid accrued interest
on: (i) all indebtedness of the Company to banks, commercial finance lenders,
insurance companies or other financial institutions regularly engaged in the
business of lending money, which is for money borrowed by the Company
(whether or not secured and whether currently existing or incurred at a later
date), and (ii) any such indebtedness or any debentures, notes or other
evidence of indebtedness issued in exchange for or to refinance any other
Senior Indebtedness, or any indebtedness arising from the satisfaction of any
other Senior Indebtedness by a guarantor.

              (b)  DEFAULT ON SENIOR INDEBTEDNESS. If there should occur any
receivership, insolvency, assignment for the benefit of creditors,
bankruptcy, reorganization or arrangements with creditors (whether or not
pursuant to bankruptcy or other insolvency laws), sale of all or
substantially all of the assets, dissolution, liquidation or any other
marshaling of the assets and liabilities of the Company, or there occurs an
event of default that has been declared in writing with respect to any Senior
Indebtedness, or in the instrument under which any Senior Indebtedness is
outstanding, then (i) no amount shall be paid by the Company in respect of
the principal of or interest on this Debenture at the time outstanding,
unless and until such event of default shall have been cured or waived or
shall have ceased to exist or the principal of and interest on the Senior
Indebtedness then outstanding shall be paid in full, and (ii) no claim or
proof of claim shall be filed with the Company by or on behalf of Holder that
shall assert any right to receive any payments in respect of the principal of
and interest on this Debenture, except subject to the payment in full of the
principal of and interest on all of the Senior Indebtedness then outstanding.

              (c)  EFFECT OF SUBORDINATION. Subject to the rights, if any, of
the holders of Senior Indebtedness under this Section 2 to receive cash,
securities or other property otherwise payable or deliverable to Holder,
nothing contained in this Section 2 shall impair, as between the Company and
Holder, the obligation of the Company, subject to the terms and conditions
hereof, to pay to Holder the principal hereof and interest hereon as and when
the same become due and payable, or shall prevent Holder, upon default
hereunder, from exercising all rights, powers and remedies otherwise provided
herein or by applicable law.

              (d)  SUBROGATION. Subject to the payment in full of all Senior
Indebtedness and until this Debenture shall be paid in full, Holder shall be
subrogated to the rights of the holders of Senior Indebtedness (to the extent
of payments or distributions previously made to such holders of Senior
Indebtedness pursuant to the provisions of Section 2(b) above) to receive
payments or distributions of

                                       2

<PAGE>

assets of the Company applicable to the Senior Indebtedness. No such payments
or distributions applicable to the Senior Indebtedness shall, as between the
Company and its creditors, other than the holders of Senior Indebtedness and
Holder, be deemed to be a payment by the Company to or on account of this
Debenture; and for the purposes of such subrogation, no payments or
distributions to the holders of Senior Indebtedness to which Holder would be
entitled except for the provisions of this Section 2 shall, as between the
Company and its creditors, other than the holders of Senior Indebtedness and
Holder, be deemed to be a payment by the Company to or on account of the
Senior Indebtedness.

              (e)  UNDERTAKING. By Holder's acceptance of this Debenture,
Holder agrees to execute and deliver such documents as may be reasonably
requested from time to time by the Company or the lender of any Senior
Indebtedness in order to implement the foregoing provisions of this Section 2.

         3.   EVENTS OF DEFAULT.

              (a)  For purposes of the Debenture, an "EVENT OF DEFAULT" shall
mean the occurrence of any of the following:

                   (i)   the Company fails to pay when due the full amount of
         interest then accrued on the Debenture, or the Company fails to pay
         when due the full amount of any principal payment on the Debenture;

                   (ii)  the Company fails to perform or observe any other
         material provision contained in the Debenture or the Warrant and
         such failure is not cured within 30 days of notice thereof from
         Holder to the Company;

                   (iii) any representation, warranty or information
         contained in the Subscription Agreement or required to be furnished
         to Holder pursuant to the Subscription Agreement, or any writing
         furnished by the Company to Holder, is false or misleading in any
         material respect on the date made or furnished; or

                   (iv)  the Company or any Subsidiary makes an assignment
         for the benefit of creditors or admits in writing its inability to
         pay its debts generally as they become due; or an order, judgment or
         decree is entered adjudicating the Company or any Subsidiary
         bankrupt or insolvent; or any order for relief with respect to the
         Company or any Subsidiary is entered under the Federal Bankruptcy
         Code; or the Company or any Subsidiary petitions or applies to any
         tribunal for the appointment of a custodian, trustee, receiver or
         liquidator of the Company or any Subsidiary, or of any substantial
         part of the assets of the Company or any Subsidiary, or commences
         any proceeding (other than a proceeding for the voluntary
         liquidation and dissolution of any Subsidiary) relating to the
         Company or any Subsidiary under any bankruptcy reorganization,
         arrangement, insolvency, readjustment of debt, dissolution or
         liquidation law of any jurisdiction; or any such petition or
         application is filed, or any such proceeding is commenced, against
         the Company or any Subsidiary and either (A) the Company or any such
         Subsidiary by any act indicates its approval thereof, consent
         thereto or acquiescence therein or (B) such petition, application or
         proceeding is not dismissed within 60 days.

                                       3

<PAGE>
              (b)  CONSEQUENCES OF EVENTS OF DEFAULT.

                   (i)   Subject to the provisions of Section 2 above, if an
         Event of Default has occurred, Holder may demand (by written notice
         delivered to the Company) immediate payment of all or any portion of
         the outstanding principal amount of the Debenture. If Holder demands
         immediate payment and all or any portion of the Debenture, the
         Company will (within 30 days after receipt of the initial request
         for payment) pay to Holder the principal amount of the Debenture
         requested to be paid (plus accrued interest thereon).

                   (ii)  Holder will also have any other rights which Holder
         may have been afforded under any contract or agreement at any time
         and any other rights which Holder may have been afforded under any
         contract or agreement at any time and any other rights which Holder
         may have pursuant to applicable law.

         4.   CONVERSION.

              (a)  CONVERSION PROCEDURE.

                   (i)   So long as Holder is not in default under
         representations, warranties or covenants of this Debenture or the
         Subscription Agreement, Holder may at any time after 90 days after the
         Closing Date convert all, but not less than all, of the outstanding
         principal amount of the Debenture and accrued interest into shares of
         Common Stock, rounded to the nearest whole share, determined pursuant
         to Section 4(b) hereof (the "CONVERSION SHARES"); provided that all
         interest accrued but unpaid with respect to the Debenture as of the
         Conversion Date shall be converted into shares of the Common Stock. The
         "CONVERSION DATE" means, for the purpose of this Agreement and with
         respect to the Debenture, the effective date, under this Debenture, of
         the Conversion Notice (as defined below) provided in accordance with
         the terms and conditions of this Debenture with respect to the
         conversion of the Debenture or the Expiration Date if the Company
         elects to convert the Debenture pursuant to this Section 4(a)(i). The
         conversion rights provided to Holder hereunder shall automatically
         terminate at the close of business on the last day of the ten-day
         period immediately following the date of the Redemption Notice (as
         defined in Section 5(b) below).

                   (ii)  Holder shall provide to the Company a written notice
         of its intent to convert all of the outstanding principal amount of
         the Debenture and accrued interest, in the form of Notice of
         Conversion set forth on Exhibit A attached hereto and made a part
         hereof by this reference, and surrender all Debentures representing
         the principal amount to be converted into the Conversion Shares (the
         "CONVERSION NOTICE"). Each such conversion of the Debenture will be
         deemed to have been effected as of the close of business on the date
         on which the Debenture has been surrendered at the principal office
         of the Company, together with a statement of Holder indicating that
         all of the outstanding principal of and accrued interest under the
         Debenture is to be converted into the Conversion Shares. At such
         time as such conversion has been effected, the rights of Holder as
         the holder of the Debenture will cease, and the Person or Persons in
         whose name or names any certificate or certificates for the
         Conversion Shares will be deemed to have become the holder or
         holders of record of the Conversion Shares represented thereby.

                                       4

<PAGE>                   (iii) Within 5 business days after a conversion has
         been effected, the Company will deliver to Holder a certificate or
         certificates representing the Conversion Shares in such name or
         names and such denomination or denominations as Holder has specified.

                         (iv)  The issuance of certificates for the Conversion
         Shares will be made without charge to Holder for any issuance tax in
         respect thereof or other cost incurred by the Company in connection
         with such conversion and the related issuance of the Conversion Shares.
         Upon conversion of the Debenture, the Company will take all such
         actions as are necessary in order to insure that the Conversion Shares
         will be validly issued, fully paid and nonassessable.

                         (v)   The Company will not close its books against the
         transfer of Common Stock issued or issuable upon conversion of the
         Debenture in any manner which interferes with the timely conversion of
         the Debenture.

                         (vi)   Notwithstanding any other provision of this
         Debenture, this Debenture may not be exercised by Holder unless at the
         time of exercise (i) a registration statement registering the
         Conversion Shares upon such exercise is effective under the Securities
         Act, or the transaction in which such Conversion Shares are to be
         issued is exempted from the application of the registration
         requirements of the Securities Act, and (ii) the Conversion Shares have
         been registered or qualified under any applicable state securities laws
         or an exemption from registration or qualification is available under
         such laws. Holder may have certain registration rights with respect to
         the Conversion Shares under the Registration Rights Agreement dated as
         of January __, 2000, between Purchaser and the Company, pursuant to
         which the holder of Conversion Shares may, in certain limited
         circumstances, obligate the Company to register or qualify such
         Conversion Shares under federal or state securities laws.

              (b)  CONVERSION RATE. The Debenture shall be convertible into
fully-paid and non-assessable shares of Common Stock of the Corporation
calculated in accordance with the following formula:

                  Number of Conversion Shares = (PRINCIPAL + INTEREST)
                                                   Conversion Price

                  As used in this Debenture:

                           The term "PRINCIPAL" shall mean the principal amount
                  of the Debenture to be converted, but in any event an amount
                  no greater than the outstanding principal of the Debenture on
                  the date of the Conversion Notice.

                           The term "INTEREST" shall mean (i) the Principal
                  multiplied by the product of (a) the quotient obtained by
                  dividing (1) the number of days from the Closing Date by (2)
                  the actual number of days in the year with respect to which
                  this calculation is being made and (b) .07 (unless adjusted in
                  accordance with Section 1 above) less (ii) the amount or
                  amounts paid by the Company to Holder in respect of interest
                  on the Debenture up to and including the date of the
                  Conversion Notice.

                                       5

<PAGE>
                           The term "CONVERSION PRICE" shall mean $5.00, as
                  adjusted in accordance with the terms and conditions of the
                  Debenture as of the date of the Conversion Notice.


              (c)  SUBDIVISION OR COMBINATION OF COMMON STOCK. If the Company
at any time subdivides (by any stock split, stock dividend or otherwise) one
or more classes of its outstanding shares of Common Stock into a greater
number of shares, the Conversion Price in effect immediately prior to such
subdivision will be proportionately reduced, and if the Company at any time
combines (by reverse stock split or otherwise) one or more classes of its
outstanding shares of Common Stock into a smaller number of shares, the
Conversion Price in effect immediately prior to such combination will be
proportionately increased. If the Purchaser is entitled to receive shares of
two or more classes of capital stock of the Company pursuant to the foregoing
upon conversion of the Debenture, the Company shall determine the allocation
of the adjusted Conversion Price between the classes of capital stock. After
such allocation, the conversion privilege and the Conversion Price of each
class of capital stock shall thereafter be subject to adjustment on terms
comparable to those applicable to Common Stock in this Debenture. An
adjustment made pursuant to this section shall become effective immediately
after the effective date of such event retroactive to the record date, if
any, for such event. Such adjustment shall be made successively whenever such
a payment, subdivision, combination or reclassification is made.

              (d)  NOTICES.

                   (i)   Immediately upon the occurrence of any event giving
         rise to any adjustment of the Conversion Price, the Company will
         send written notice thereof to Holder.

                   (ii)  The Company will send written notice to Holder at least
          20 days prior to the date on which the Company closes its books or
          takes a record with respect to any dividend or distribution upon the
          Common Stock.

         5.   REDEMPTION.

              (a)  COMPANY'S RIGHT TO REDEEM. The Company shall have the
right to redeem this Debenture by payment to Holder of the face value of this
Debenture plus any accrued but unpaid interest thereon, at any time from and
after the date upon which (a) the average Market Price of the Common Stock
for a period of 60 consecutive calendar days equals or exceeds $7.50; and (b)
either the Conversion Shares have been registered for sale under the
Securities Act, or this Debenture has been issued to Holder (or any successor
or assign thereof) for more than one year so that Holder (or any successor or
assign thereof) may sell any Conversion Shares under Rule 144 promulgated
under the Securities Act; provided, however, that such redemption shall not
become effective prior to the last day of the ten-day period immediately
following the date of the Redemption Notice. If the Company elects to redeem
this Debenture, it must redeem all outstanding Debentures. The Company shall
not have the right to redeem the Debenture when an Event of Default, or an
event which, with notice or lapse of time or both, would constitute an Event
of Default, has occurred and is continuing.

              (b)  REDEMPTION PROCEDURE. Holder shall, within 30 days of the
date of written notice from the Company of the redemption of all of the
outstanding Debentures (the "REDEMPTION NOTICE"),

                                       6

<PAGE>

surrender the original executed copy of this Debenture at the principal
business office of the Company (or such other place as may be designated by the
Company in such notice) (the thirtieth day following the Redemption Notice being
the "REDEMPTION DATE"). The Company shall pay the Redemption Price for this
Debenture within five days of the date of such surrender.

              (c)  RIGHTS AFTER REDEMPTION DATE. On the Redemption Date, all
rights of Holder, as holder of this Debenture, other than the right to
payment of the Redemption Price for this Debenture, shall cease, and this
Debenture shall be deemed to be cancelled and no longer outstanding. Upon
payment of the Redemption Price for this Debenture, all rights of Holder, as
holder of this Debenture, shall cease.

              (d)  DATE OF REDEMPTION NOTICE. The date of the Redemption
Notice shall be the third business day immediately following the day on which
such notice is sent by the Company if sent by certified or registered mail,
return receipt requested, or the business day immediately following the day
on which such notice is sent by the Company if sent by overnight courier.

         6.   PROHIBITION ON DIVIDENDS. Until the Expiration Date, the
Company shall not declare nor pay any dividend with respect to the Common
Stock other than a stock dividend.

         7.   AMENDMENT AND WAIVER. Except as otherwise expressly provided
herein, the provisions of the Debenture may be amended and the Company may
take any action herein prohibited, or omit to perform any act herein required
to be performed by it, only if the Company has obtained the written consent
of Holder.

         8.   DEFINITIONS. For purposes of the Debenture, the following
capitalized terms have the following meaning.

         "CLOSING" means the closing of the offering of the Debentures.

         "CLOSING DATE" means the date of the Closing.

         "COMMON STOCK" means, collectively the Company's Common Stock, $.25 par
value, and any capital stock of any class of the Company hereafter authorized
which is not limited to a fixed sum or percentage of par or stated value in
respect to the rights of the holders thereof to participate in dividends or in
the distribution of assets upon any liquidation, dissolution or winding up of
the Company.

         "MARKET PRICE" of any security means the average of the closing prices
of such security's sales on all securities exchanges on which such security may
at the time be listed, or, if there has been no sales on any such exchange on
any day, the average of the highest bid and lowest asked prices on all such
exchanges at the end of such day, or, if on day any such security is not so
listed, the average of the representative bid and asked prices quoted in the
NASDAQ System as of 4:00 P.M., New York time, or if on any day such security is
not quoted in the NASDAQ System, the average of the highest bid and lowest asked
prices on such day in the domestic over-the-counter market as reported by the
National Quotation Bureau, Incorporated, or any similar successor organization,
in each such case averaged over a period of 21 days consisting of the day as of
which "Market Price" is being determined and the 20 consecutive business days
prior to such day. If at any time such security is not listed on any securities
exchange or quote in the NASDAQ System or the over-the-counter market, the
"Market Price" will be fair value thereof determined jointly by the Company and
Holder. If such parties are unable to reach agreement

                                       7

<PAGE>

within a reasonable period of time, such fair value will be the fair value
thereof as reasonably determined by the Company's Board of Directors.

         "PERSON" means an individual, a partnership, a corporation, an
association, a joint stock company, a trust, a joint venture, an unincorporated
organization and a governmental entity or any department, agency or political
subdivision thereof.

         "SUBSIDIARY" means any corporation of which the shares of stock having
a majority of the general voting power in electing the board of directors are,
at the time as of which any determination is being made, owned by the Company
either directly or indirectly through Subsidiaries.

         9.   TRANSFER.

              (a)  This Debenture may not be assigned or transferred except
as provided herein and in accordance with and subject to the provisions of
the Securities Act and any applicable state securities laws. Any purported
transfer or assignment made other than in accordance with this Section 9
shall be null and void and of no force and effect.

              (b)  This Debenture shall be transferable only upon the receipt
of an opinion of counsel satisfactory to the Company to the effect that (i)
the transferee is a person to whom the Debenture may be legally transferred
without registration under the Securities Act or any state securities laws;
and (ii) such transfer will not violate any applicable law or governmental
rule or regulation including, without limitation, any applicable federal or
state securities law. Prior to any transfer or assignment of this Debenture,
the assignor or transferor shall reimburse the Company for its reasonable
expenses, including attorneys' fees, incurred in connection with the transfer
or assignment.

              (c)  Any assignment permitted hereunder shall be made by
surrender of this Debenture to the Company at its principal office with a
duly executed Assignment Form, set forth on Exhibit B attached hereto and
made a part hereof by this reference, and funds sufficient to pay any
transfer tax. In such event, the Company shall, without charge, execute and
deliver a new Debenture in the name of the assignee named in such Assignment
Form, and this Debenture shall promptly be cancelled. This Debenture may be
divided or combined with any of the Debentures which carry the same rights
upon presentation thereof at the principal office of the Company together
with a written notice signed by the Holder thereof, specifying the names and
denominations in which certificates representing new Debentures are to be
issued. The term "Debenture" as used herein includes any of the Debentures
issued in substitution for or replacement of this Debenture, or into which
this Debenture may be divided or exchanged.

              (d)  Upon receipt by the Company of evidence satisfactory to it
of the loss, theft, destruction or mutilation of this Debenture or any stock
certificate representing Conversion Shares issued upon the exercise hereof
and, in the case of any such loss, theft or destruction, upon receipt of an
indemnity reasonably satisfactory to the Company, and, in the case of any
such mutilation, upon surrender and cancellation of this Debenture or such
stock certificate, the Company will execute and deliver a new Debenture or
stock certificate of like tenor and date, and any such lost, stolen,
destroyed or mutilated Debenture or stock certificate shall thereupon become
void.

                                       8

<PAGE>

              (e)  Holder and each holder of the Conversion Shares or any
other security issued or issuable upon exercise of this Debenture shall
indemnify and hold harmless the Company, its directors and officers, and each
person, if any, who controls the Company, against any losses, claims, damages
or liabilities, joint or several, to which the Company or any such director,
officer or any such person may become subject under the Securities Act or any
statute or common law, insofar as such losses, claims, damages or
liabilities, or actions in respect thereof, arise out of or are based upon
the disposition by Holder or such holder of the Conversion Shares or other
such securities in violation of the terms of this Debenture.

              (f)  This Debenture and the Conversion Shares or any other
security issued or issuable upon exercise of this Debenture may not be sold,
transferred or otherwise disposed of except to a person who, in the opinion
of counsel reasonably satisfactory to the Company, is a person to whom this
Debenture or such Conversion Shares may legally be transferred pursuant to
the provisions of Sections 9(a) and (b) above without registration and
without the delivery of a current prospectus under the Securities Act with
respect thereto and then only against receipt of an agreement of such person
to comply with the provisions of this Section 9 with respect to any resale or
other disposition of such securities unless, in the opinion of such counsel,
such agreement is not required.

              (g)  Holder, by acceptance of this Debenture, agrees that the
Conversion Shares to be issued upon exercise hereof are being acquired for
the account of Holder for investment and not with a view to, or for resale in
connection with, the distribution thereof and that Holder will not offer,
sell or otherwise dispose of such Conversion Shares except under
circumstances which will not result in a violation of the Securities Act and
all applicable state securities laws. Holder represents that Holder has no
present intention of distributing or reselling the Conversion Shares.

              (h)  The Company may cause the following legend, or one of
similar substance, to be set forth on each certificate representing
Conversion Shares or any other security issued or issuable upon exercise of
this Debenture, unless counsel for the Company is of the opinion as to any
such certificate that such legend is unnecessary:

         THE SECURITIES OF SENTO CORPORATION, A UTAH CORPORATION (THE
         "COMPANY"), EVIDENCED BY THIS CERTIFICATE HAVE NOT BEEN
         REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE
         SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON
         EXEMPTIONS FROM THE REGISTRATION REQUIREMENTS OF THE
         SECURITIES ACT OF 1933, AS AMENDED, AND VARIOUS APPLICABLE
         STATE SECURITIES LAWS. THE SECURITIES MAY NOT BE SOLD,
         TRANSFERRED, PLEDGED OR ASSIGNED OR A SECURITY INTEREST
         CREATED THEREIN, UNLESS THE PURCHASE, TRANSFER, ASSIGNMENT,
         PLEDGE OR GRANT OF SUCH SECURITY INTEREST COMPLIES WITH ALL
         STATE AND FEDERAL SECURITIES LAWS (I.E., SUCH SHARES OF
         COMMON STOCK ARE REGISTERED UNDER SUCH LAWS OR AN EXEMPTION
         FROM REGISTRATION IS AVAILABLE THEREUNDER) AND UNLESS THE
         SELLER, TRANSFEROR, ASSIGNOR, PLEDGOR

                                       9

<PAGE>

         OR GRANTOR OF SUCH SECURITY INTEREST PROVIDES AN OPINION OF
         COUNSEL REASONABLY SATISFACTORY TO THE COMPANY THAT THE
         TRANSACTION CONTEMPLATED WOULD NOT BE IN VIOLATION OF THE
         SECURITIES ACT OF 1933, AS AMENDED, OR ANY APPLICABLE STATE
         SECURITIES LAWS. TRANSFERABILITY OF THE SECURITIES IS
         THEREFORE LIMITED AND INVESTORS MUST BEAR THE ECONOMIC RISK
         OF THEIR INVESTMENT FOR AN INDEFINITE PERIOD OF TIME.

         10.  CANCELLATION. After all principal and accrued interest at any
time owned on the Debenture has been paid in full, the Debenture will be
surrendered to the Company for cancellation and will not be reissued.

         11.  PLACE OF PAYMENT. Payments of principal and interest are to be
delivered to the Purchaser as follows:


                           ABA #[______________]
                           Account #[______________]
                           [_______________________]

Or to such other address or to the attention of such other person as specified
by prior written notice to the Company.

         12.  GOVERNING LAW. This Debenture shall be construed and
interpreted according to the laws of the State of Utah without giving effect
to the principles of conflicts of law thereof.

         IN WITNESS WHEREOF, the Company has executed and delivered this
Debenture on ___________ ___, 2000.

                                            SENTO CORPORATION


                                            By:
                                                -------------------------------
                                            Name:
                                                  -----------------------------
                                            Title:
                                                   ----------------------------


                                       10
<PAGE>

                                    EXHIBIT A


                              NOTICE OF CONVERSION



TO:      SENTO CORPORATION (the "COMPANY"):


         1.   The undersigned holder of the attached debenture (the
"DEBENTURE") hereby elects to convert the outstanding principal of the
Debenture (together with accrued and unpaid interest thereon) into the number
of shares of the Common Stock determined in accordance with the terms and
conditions of the Debenture. Terms used but not defined herein shall have the
meaning set forth in the Debenture.

         2.   Please issue a certificate or certificates representing the
Conversion Shares in the name of the undersigned.


---------------
     (DATE)


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                                    EXHIBIT B


                                 ASSIGNMENT FORM


                                                     Dated: ____________________


        FOR VALUE RECEIVED, _____________________ ("ASSIGNOR") hereby sells,
assigns, and transfers unto ______________________ (please type or print)
______________________________ (address) the rights of Assignor under the
debenture attached hereto (the "DEBENTURE") to the extent of $_______ of the
outstanding principal amount of the Debenture and does hereby irrevocably
constitute and appoint Sento Corporation (the "COMPANY") and/or its transfer
agent as attorney to transfer the same on the books of the Company with full
power of substitution in the premises.



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