Ubuntu Manpage: DS1991 - 1152bit MultiKey iButton

Provided by: owfs-doc_3.2p4+dfsg1-4.1build1_all

NAME

       DS1991 - 1152bit MultiKey iButton

SYNOPSIS

       Non-volatile memory with password protection.

       02   [.]XXXXXXXXXXXX[XX][/[   subkey0/reset.    hex_pwd  |  subkey0/password.   hex_pwd  |
       subkey0/secure_data.  hex_pwd | subkey0/id.  hex_pwd

       02  [.]XXXXXXXXXXXX[XX][/[  subkey1/reset.   hex_pwd  |   subkey1/password.    hex_pwd   |
       subkey1/secure_data.  hex_pwd | subkey1/id.  hex_pwd

       02   [.]XXXXXXXXXXXX[XX][/[   subkey0/reset.    hex_pwd  |  subkey2/password.   hex_pwd  |
       subkey2/secure_data.  hex_pwd | subkey2/id.  hex_pwd address |  crc8  |  id  |  locator  |
       r_address | r_id | r_locator | type ]]

FAMILY CODE

SPECIAL PROPERTIES

   subkey[0|1|2]/reset.hex_pwd
       write-only, yes-no
       Initialize one of the three secure data areas and set a new password.

       The   extension   (hex_pwd)   is   the   new   8-byte   password   in   hexadecimal  (e.g.
       password.000204006080A0C0E for bytes 0,2,4,6,8,10,12,14)

       The data must be "1" or "yes" to actually reset the subkey.

       Note: writing a password will clear any existing data and ID.

   subkey[0|1|2]/password.hex_pwd
       write-only, binary
       Change the password of one of the secure subkey areas without losing data.

       The  extension  (hex_pwd)  is  the  existing  8-byte   password   in   hexadecimal   (e.g.
       password.00020406080A0C0E for bytes 0,2,4,6,8,10,12,14)

       The data portion is 8 bytes that will be used as a new password.

   subkey[0|1|2]/secure_data.hex_pwd
       read-write, binary
       Read or write data in one of the three sucure data areas.

       The   extension   (hex_pwd)   is   the  existing  8-byte  password  in  hexadecimal  (e.g.
       password.00020406080A0C0E for bytes 0,2,4,6,8,10,12,14)

       The data portion binary data. Up to 48 bytes in each subkey area, starting at location  0.
       If the wrong password is specified, "random data" is returned on read and data is silently
       ignored on write.

   subkey[0|1|2]/id.hex_pwd
       read-write, binary
       Read or write the subkey id.

       The  extension  (hex_pwd)  is  the  existing  8-byte   password   in   hexadecimal   (e.g.
       password.00020406080A0C0E for bytes 0,2,4,6,8,10,12,14)

       The data portion 8 binary bytes. This is the subkey id.  The correct password must be used
       to write a new id but not to read it.

STANDARD PROPERTIES

address
r_address
read-only, ascii
The entire 64-bit unique ID. Given as upper case hexadecimal digits (0-9A-F).
address starts with the family code
r address is the address in reverse order, which is often used in other applications and
labeling.

crc8
read-only, ascii
The 8-bit error correction portion. Uses cyclic redundancy check. Computed from the
preceding 56 bits of the unique ID number. Given as upper case hexadecimal digits (0-9A-
F).

family
read-only, ascii
The 8-bit family code. Unique to each type of device. Given as upper case hexadecimal
digits (0-9A-F).

id
r_id
read-only, ascii
The 48-bit middle portion of the unique ID number. Does not include the family code or
CRC. Given as upper case hexadecimal digits (0-9A-F).
r id is the id in reverse order, which is often used in other applications and labeling.

locator
r_locator
read-only, ascii
Uses an extension of the 1-wire design from iButtonLink company that associated 1-wire
physical connections with a unique 1-wire code. If the connection is behind a Link Locator
the locator will show a unique 8-byte number (16 character hexadecimal) starting with
family code FE.
If no Link Locator is between the device and the master, the locator field will be all FF.
r locator is the locator in reverse order.

present (DEPRECATED)
read-only, yes-no
Is the device currently present on the 1-wire bus?

type
read-only, ascii
Part name assigned by Dallas Semi. E.g. DS2401 Alternative packaging (iButton vs chip)
will not be distiguished.

ALARMS

       None.

DESCRIPTION

1-Wire
1-wire is a wiring protocol and series of devices designed and manufactured by Dallas
Semiconductor, Inc. The bus is a low-power low-speed low-connector scheme where the data
line can also provide power.

Each device is uniquely and unalterably numbered during manufacture. There are a wide
variety of devices, including memory, sensors (humidity, temperature, voltage, contact,
current), switches, timers and data loggers. More complex devices (like thermocouple
sensors) can be built with these basic devices. There are also 1-wire devices that have
encryption included.

The 1-wire scheme uses a single bus master and multiple slaves on the same wire. The bus
master initiates all communication. The slaves can be individually discovered and
addressed using their unique ID.

Bus masters come in a variety of configurations including serial, parallel, i2c, network
or USB adapters.

OWFS design
OWFS is a suite of programs that designed to make the 1-wire bus and its devices easily
accessible. The underlying principle is to create a virtual filesystem, with the unique ID
being the directory, and the individual properties of the device are represented as simple
files that can be read and written.

Details of the individual slave or master design are hidden behind a consistent interface.
The goal is to provide an easy set of tools for a software designer to create monitoring
or control applications. There are some performance enhancements in the implementation,
including data caching, parallel access to bus masters, and aggregation of device
communication. Still the fundamental goal has been ease of use, flexibility and
correctness rather than speed.

DS1991
The DS1991 (3) is an iButton with password protected non-volatile memory. Data is
read/written with error checking (transparent to the user). The memory is divided into 3
different pages with 3 separate passwords.

In theory, choosing an incorrect password is hard to discern because the chip responds
normally but with incorrect data. There is a published analysis suggesting that the
"random data" follows a pattern and so a concerted attack might be successful.

The password (in hexadecimal) is used a the file extension 02.1234123414/subkey0/id.
password allowing a password to be passed to the program within the filesystem paradigm.

ADDRESSING

       All  1-wire  devices  are factory assigned a unique 64-bit address. This address is of the
       form:

       Family Code
              8 bits

       Address
              48 bits

       CRC    8 bits

       Addressing under OWFS is in hexadecimal, of form:

              01.123456789ABC

       where 01 is an example 8-bit family code, and 12345678ABC is an example 48 bit address.

       The dot is optional, and the CRC code can included. If included, it must be correct.

DATASHEET

       http://pdfserv.maxim-ic.com/en/ds/DS1991.pdf

AVAILABILITY

       http://www.owfs.org

AUTHOR

       Christian Magnusson (mag@mag.cx) and Paul Alfille