Index it to inflation rather than wages. Choose a fixed basket of goods, compute their price in the future, adjust SS accordingly.
I.e., cause SS to provide a fixed standard of living, rather than an increasing one. Seniors will always live as well in the future as they do today, they just won't live as well as future wage earners.
Also remove the cap at which you no longer collect SS from payrolls. It's something around $105,000. You don't get taxed for SS on any income past that amount. The SS tax structure is one of the most regressive taxes we have.
Social Security is the easier to fix (IMHO). The nice thing about it is that it's a service for which there are a lot of examples. The basic premise that you put away money for your retirement and that money grows over time is pretty simple and sound. You could streamline it a bit to reduce overhead. Yes, the way it works now is somewhat broken (e.g.: I am not "saving" currently, but paying for people who are now retired, hoping that my grandchildren will pay for me), but in principle it needs only minor adjustments.
Medicare on the other hand is growing very rapidly and the broken healthcare system will only speed up its growth. I don't see a way to fix it without dismantling it and starting over. Not that I am in the Ryan camp: I am not advocating leaving seniors out in the cold. I am just saying that Medicare will require more than minor adjustments.
In current law it is already fixed. When it runs out of bonds in the "trust fund," it will automatically decrease its payouts to become revenue neutral.
I'm not sure what I've said to suggest that I'd like to buy a bridge (presumably contained in a dry region of a landlocked state). The discussion is about fixes to a perceived problem, but the problem will fix itself if the legislature does precisely nothing. I expect it is easier to get it to accomplish nothing than to accomplish any particular other solution.