DS1991(3) One-Wire File System DS1991(3)NAMEDS1991 - 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 ]]
FAMILY CODE
02
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 hexidecimal (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 hexidecimal
(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 hexidecimal
(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 hexidecimal
(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 PROPERTIESALARMS
None.
DESCRIPTIONDS1991
The DS1991 (3) is an iButton with password protected non-volatile mem‐
ory. 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 pub‐
lished analysis suggesting that the "random data" follows a pattern and
so a concerted attack might be successful.
The password (in hexidecimal) is used a the file extension
02.1234123414/subkey0/id. password allowing a password to be passed to
the program within the filesystem paradigm.
ADDRESSINGDATASHEET
http://pdfserv.maxim-ic.com/en/ds/DS1991.pdf
SEE ALSOAVAILABILITY
http://www.owfs.org
AUTHOR
Christian Magnusson (mag@mag.cx) and Paul Alfille
OWFS Manpage 2003 DS1991(3)
