**EXHIBIT
      31.1**





**CERTIFICATION**





I,
      Terry
      R. Gibson, certify that:





1.  I
      have
      reviewed this quarterly report on Form 10-Q of CoSine Communications,
      Inc.;





2.  Based
      on my
      knowledge, this report does not contain any untrue statement of a material
      fact
      or omit to state 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
      this report, fairly present in all material respects the financial condition,
      results of operations and cash flows of the registrant as of, and for, the
      periods presented in this report;





4.  The
      registrant's other certifying officer 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 registrant 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 registrant is made known to us by others within
      those entities, particularly during the period in which this report is being
      prepared;




b) designed such
      internal control over financial reporting, or caused such internal control
      over
      financial reporting to be designed under our supervision, to provide reasonable
      assurance regarding the reliability of financial reporting and the preparation
      of financial statements for external purposes in accordance with generally
      accepted accounting principles;




c) evaluated the
      effectiveness of the registrant'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





d) disclosed in this
      report any change in the registrant's internal control over financial reporting
      that occurred during the registrant's most recent fiscal quarter (the
      registrant's fourth fiscal quarter in the case of an annual report) that has
      materially affected, or is reasonably likely to materially affect, the
      registrant's internal control over financial reporting; and





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





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 registrant'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
      a
      significant role in the registrant's internal control over financial reporting.








/s/
      Terry R. Gibson


Terry
      R.
      Gibson


Chief
      Executive Officer and Chief Financial Officer


August
      11, 2008