def list(filter = nil)
      @backend.transaction(true){
        result = @backend[:user].keys.collect{|k| decrypt(k)}

        if filter.blank?
          result
        else
          result.select{|k,v| k =~ /#{filter}/}
        end
      }
    end
def list(filter = nil)
      @backend.transaction(true){
        result = @backend[:user].keys.collect{|k| decrypt(k)}

        if filter.blank?
          result
        else
          result.select{|k,v| k =~ /#{filter}/}
        end
      }
    end
Return all keys, optionally filtered by filter