Ubuntu Manpage: DS1991 - 1152bit MultiKey iButton

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 fundemental 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