Topic: Ultralight C 3des key change

Hi all , I'm trying to change the 3des key on an Ultrilight C card, I can write the the values in to the address 44-47 as I've found in some topics here, but I cannot authenticate when using it, if I write back the default key it works with no problems.
I think there's something I don't understand that's maybe the source of the problem, looking at the freefare library examples and in some posts from this forum I've found the default key in ultralight c is: "425245414b4d454946594f5543414e21" (hex values for ascii "BREAKMEIFYOUCAN!") , but for decrypting it on client the key used "49454D4B41455242214E4143554F5946". I don't know what's the relation between both keys, but I think some predified operation needs to be done in order to generate one from the other, and that's the cause of my failures. Every help is appreciated.

This is the example I'm using for testing … fo.c?r=994

Re: Ultralight C 3des key change

if the hex key is: "00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F" then you have to write the sequence "07 06 05 04 03 02 01 00 0F 0E 0D 0C 0B 0A 09 08" in 4 pages, starting from page 0x2C (in decimal, 16 bytes starting from page 44).