Does the variable interest rate on bank certificates avert usury, and what is the lawful alternative for financial transactions if that is forbidden?

The certificates issued by usurious banks are part of forbidden usury, and their nature is not altered by a change in percentage from one year to another. The legitimate alternative is to invest money in a lawful manner through Mudarabah (definition) (profit-sharing) or trade, or other forms of permissible earning. This includes Mudarabah in money through Islamic banks that adhere to the regulations of Sharia (definition).