This quickie will show you How to Draw a Key using Inkscape.
Draw an Ellipse and give it a gray color.
Then Draw a vertically long Rectangle and place it ontop of the circle near the bottom.
Select them both and use Union to combine them ('CTRL' + '+').
Draw another smaller Circle, and place it at the top center of your shape.
Then take the Difference of both shapes. ('CTRL' + '-')
Take your Node Tool and Create 2 more nodes at the bottom.
Grab the two other nodes at the corners and drag them upwards.
Now Draw a random jagged shape to be your key design.
Take the Difference of both shapes. ('CTRL' + '-')
Next, Draw 2 rectangles with your Pen Tool, following the shape the bottom of the key has.
(Hold the CTRL key while Drawing to keep your lines straight)
Now Redraw your random jagged shape by using your Pen Tool to trace the outline it made. (shown in green)
Use Difference with the Trace shape and each of the rectangles that overlap with it to get rid of any stray lines.
Fill these Rectangles in with a darker shade than your key.
You have now Drawn your very own Key.