I think you are on windows machine and your home is abc
When you run bellow command
keytool -genkey -alias tomcat -keyalg RSA
As you are not specifying an explicit keystore it will try to generate keystore C:\users\abc>.keystore and also you need to provide old password for .keystore I think you are providing your version a new one.
delete .keystore from C:\users\abc> location and try the command
or try following command which will create a new xyzkeystore:
keytool -genkey -keystore xyzkeystore -alias tomcat -keyalg RSA