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cosmic

Contributor

Registered: 2019-03-18

Posts: 6

How to change/enable password as well as how to disable the password?

Hey everyone,

I was wondering how to do the following tasks:
1) Change/Set Password
2) Enable Password
3) Disable Password

To complement this question/post, I have been following along with the following t55xx datasheet:
http://www.rfidshop.com.hk/datasheet/T5 … asheet.pdf

I have searched the forums only to find one related post:
http://www.proxmark.org/forum/viewtopic.php?id=3655

In the post they mention that entering the password is done like so:

proxmark3> lf t55xx write b 7 d DEADBEEF
Writing page 0  block: 07  data: 0xDEADBEEF

This command makes sense to me as on the t55xx datasheet, it's clear that:

When password mode is active (PWD = 1), the first 32 bits after the opcode are regarded as thepassword. They are compared bit by bit with the contents of block 7

However to enable the password the other post on this forum mentions to do the following:

proxmark3> lf t55xx write b 0 d 00148050
Writing page 0  block: 00  data: 0x00148050

On the t55xx datasheet, it mentions that block 0 is the config block.
On Page 4 of the PDF and on figure 3-2, it shows that the PWD bit is bit 28 of block 0.

So why are the following commands written like so? Why don't they just flip a bit instead or call another utility function? I fear sending the wrong data could brick the chip:

 lf t55xx write b 0 d 00148050 

- to enable the password

I assume it's because this value

00148050 == 101001000000001010000 in binary

But this value is only 22 bits long.

So given this information, what would be the correct way to disable a password?

marshmellow

Contributor

From: US

Registered: 2013-06-10

Posts: 2,302

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Re: How to change/enable password as well as how to disable the password?

to change even a single bit in the config block you have to write the entire block over again. 

so, yes, make sure it is the entire config you want...

also,
00148050 = 00000000000101001000000001010000 - not what you posted.