Exhibit 99.1 CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002 In connection with the Quarterly Report of IndyMac Bancorp, Inc. (the "Company") on Form 10-Q for the period ending June 30, 2002 as filed with the Securities and Exchange Commission on the date hereof (the "Report"), the undersigned, Michael W. Perry, Vice Chairman of the Board of Directors and Chief Executive Officer of the Company, and Scott Keys, Executive Vice President and Chief Financial Officer of the Company, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that: (1) The Report fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934; and (2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company. /s/ Michael W. Perry /s/ Scott Keys - --------------------------------------- ------------------------------- Michael W. Perry Scott Keys Vice Chairman of the Board of Directors Executive Vice President and Chief and Chief Executive Officer Financial Officer August 13, 2002 August 13, 2002