**EXHIBIT
        31.1**
 
 **CERTIFICATION**
 
 I,
        Terry
        R. Gibson, certify that:
 
 1.
        I have
        reviewed this annual report on Form 10-K 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, 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 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
 
 c)
        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
 Director,
        Chief Executive Officer and Chief Financial Officer
 March
        24,
        2006