JavaCard OS

My javacard's S_ENC, S_MAC and DEK keys are default value: 40 41 42 43 44 45 46 47 48 49 4A 4B 4C 4D 4E 4F.

Q: How can i change these keys ? Should I use any tools ?

I use an internal tool to change the default key values.
You can use tool like the pyApdutool to do GP authentication, and send PUT KEY command, you can construct this command data as the GP specification descripted.