EXHIBIT 12.1

CERTIFICATIONS

I, Jacob (Yanki) Margalit, certify
that:

|1. | I
have reviewed this annual report on Form 20-F of Aladdin Knowledge Systems Ltd.;
|-- | ----------------------------------------------------------------------------------

|2. | Based
on my knowledge, this report does not contain any untrue statement of a material fact or
omit a material fact          necessary to make the statements made, in light of the
circumstances under which such statements were made, not misleading          with respect
to the period covered by this report;
|-- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

|3. | Based
on my knowledge, the financial statements, and other financial information included in
his report, fairly present in          all material respects the financial condition,
results of operations and cash flows of the company as of, and for, the          periods
presented in this report;
|-- | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

|4. | The
company's other certifying officer(s) and I are responsible for establishing and
maintaining disclosure controls and          procedures (as defined in Exchange Act Rules
13a-15(e) and 15d-15(e)) for the company and have:
|-- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (a) | Designed
such disclosure controls and procedures, or caused such disclosure controls and
procedures to be designed under our                   supervision, to ensure that
material information relating to the company, including its consolidated subsidiaries,
                  is made known to us by others within those entities, particularly
during the period in which this report is being                   prepared;
| | --- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (b) | Evaluated
the effectiveness of the company's disclosure controls and procedures and presented in
this report our conclusions                   about the effectiveness of the disclosure
controls and procedures, as of the end of the period covered by this
                  report based on such evaluation; and
| | --- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (c) | Disclosed
in this report any change in the company's internal control over financial reporting that
occurred during the                   period covered by the annual report that has
materially affected, or is reasonably likely to materially affect, the
                  company's internal control over financial reporting; and
| | --- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

|5. | The
company's other certifying officer(s) and I have disclosed, based on our most recent
evaluation of internal control over          financial reporting, to the company's
auditors and the audit committee of the company's board of directors (or persons
         performing the equivalent functions):
|-- | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (a) | All significant
      deficiencies and material weaknesses in the design or operation of internal
      control over financial reporting which are reasonably likely to adversely
      affect the company's ability to record, process, summarize and report financial
      information; and
| | --- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (b) | Any
fraud, whether or not material, that involves management or other employees who have
significant role in the                   company's internal control over financial
reporting.
| | --- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Dated: May 31, 2005

| | By: /s/
      Jacob (Yanki) Margalit
              Jacob (Yanki) Margalit
              Chief Executive Officer
              (Principal Executive Officer)
| | -----------------------------------------------------------------------------------------------------------------------------------------------------------

-62-

---