1 EXHIBIT 11.1 RSA SECURITY INC. AND SUBSIDIARIES COMPUTATION OF INCOME PER COMMON AND COMMON EQUIVALENT SHARE THREE AND NINE MONTHS ENDED SEPTEMBER 30, 1999 AND 1998 (IN THOUSANDS, EXCEPT PER SHARE DATA) THREE MONTHS ENDED NINE MONTHS ENDED SEPTEMBER 30, SEPTEMBER 30, ------------------ ------------------ 1999 1998 1999 1998 ------- ------- ------- ------- Basic earnings per share: Net income per common share....................... $ 1.50 $ .08 $ 3.64 $ .41 ======= ======= ======= ======= Weighted average number of shares outstanding... 38,988 41,186 39,205 40,958 ======= ======= ======= ======= Diluted earnings per share: Net income per common share..................... $ 1.42 $ .08 $ 3.44 $ .40 ======= ======= ======= ======= Shares: Weighted average number of shares outstanding... 38,988 41,186 39,205 40,958 Effect of dilutive options...................... 2,314 615 2,212 1,049 ------- ------- ------- ------- Adjusted weighted average number of shares outstanding....................................... 41,302 41,801 41,417 42,007 ======= ======= ======= =======