DS1991 - 1152bit MultiKey iButton

NAME SYNOPSIS FAMILY CODE SPECIAL PROPERTIES subkey[0|1|2]/reset.hex_pwd subkey[0|1|2]/password.hex_pwd subkey[0|1|2]/secure_data.hex_pwd subkey[0|1|2]/id.hex_pwd STANDARD PROPERTIES ALARMS DESCRIPTION DS1991 ADDRESSING DATASHEET SEE ALSO AVAILABILITY AUTHOR

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 ]]

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.

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.