There are many programmers on the market with PCF79xx MCU support. With the help of it, you can perform read, edit and write MCU data; So, renewing of the keys also. Some of such tools (e.g. Barracuda, RemUnlocker) renew the keys in automatic mode. Others (e.g. PCFprog) require to have "virgin" files for renew used keys.
In Smart Keys based on PCF79xx MCU can find PCF7922, PCF7941, PCF7961, PCF7945, PCF7952, PCF7953 and other MCU's.
In most cases desoldering or troublesome connection of wires to feet of MCU is not required; Most keys have "points" at the PCB for fast and easy connection of the key to the programmer. Bellow can find links to several descriptions of the keys with connection instructions:
