rkey.1

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rkey(1) Qualcomm Atheros Open Powerline Toolkit rkey(1)

NAME
rkey - HomePlug AV Random Key Generator

SYNOPSIS
rkey [options] file

DESCRIPTION
Dynamically generate distinct HomePlug AV compliant keys. A new key is printed on stdout with each program invocation or
iteration, unless this is suppressed. Key computation is seeded using a 64 ASCII character string stored in a user cre‐
ated seedfile. The program automatically increments the seedfile string to preserve continuity and uniqueness across
program invocations, program iterations, console sessions, host reboots and production sites.

This program is part of the Qualcomm Atheros Powerline Toolkit. See the AMP man page for an overview and installation
instructions.

OPTIONS
-D Uses HomePlug AV rules for computing a Device Access Key (DAK) from a pass phrase. A DAK is 16 bytes expressed as
32 hexadecimal digits. This option over-rides any -M and -N options previously specified on the command line.

-L level
Set security level. The security level is encoded into the NID. Level 0 enables pushbutton pairing. Level 1
disables it. This option has no effect unless a NID is computed.

-M Uses HomePlug AV rules for computing a Network Membership Key (NMK) from a pass phrase. An NMK is 16 bytes
expressed as 32 hexadecimal digits. This option over-rides any -D or -N options previsously specified on the com‐
mand line.

-N Uses HomePlug AV rules for computing a Network Identification Key (NID) from a pass phrase. An NID is 7 bytes
expressed as 14 hexadecimal digits. This option over-rides any -D or -M options previously specified on the com‐
mand line.

-n count
The number of keys to generate and print. This program prints the specified number of distinct keys of the speci‐
fied type, one key per line. Normally, program output is directed to a file or a pipe when this option is used.
It is useful for creating a file of random keys.

-o Use the old seedfile string. This option prevents the seedfile string from being incremented before a new key is
computed. This feature allows additional key types to be computed from the same seedfile string.

-q Enable quiet mode which, for this application, has no effect.

-v Enable verbose mode which, for this application, prints the pass phrase for each key.

--?, --help
Print program help summary on stdout. This option takes precedence over other options on the command line.

-!, --version
Print program version information on stdout. This option takes precedence over other options on the command line.
Use this option when sending screen dumps to Atheros Technical Support so that they know exactly which version of
the Linux Toolkit you are using.

ARGUMENTS
seedfile
The text file containing the seed string. This file may be any length but only the first 64 characters are sig‐
nificant. If it is less than 64 characters then it will be extended to 64 characters after the first use. The
full 64 character string is incremented, character by character, right to left each time this program is run. The
seedfile string is salted differently for each type of key requested and used to seed the SHA256 key engine. One
property of the SHA256 algorithm is that small changes in the seed will produce radically different output having
an extremely small chance of collision.

EXAMPLES
The following example shows how to create a seedfile. The seedfile acts as the seed for the SHA256 algorithm. The seed
is then salted (modified) differently for each type of key generated by this program. The seedfile string is then incre‐
mented and re-written each time the program is executed, unless behaviors is suppressed. Initially, the seedfile must
contain at least one character or an error will occur.

# echo "My Company Name, Inc." > secret.key

The following example prints an SHA256 key on stdout. An SHA256 key is 256 bits or 32 bytes expressed as 64 hexadecimal
digits. An SHA256 key is the default output when no key type is specified. SHA256 is a public domain standard, not a
HomePlug AV standard.

# rkey secret.key
BFF0F6E3C83CE13829EA7F1F6D25042F4B05052E44C0B801EEA7CD6317F3622E

The following command prints a new Device Access Key (DAK) on stdout using the seedfile secret.key as the seed. The key
will be different each time this program is executed because the seedfile string is incremented each time.

# rkey -D secret.key
F084B4E8F6069FF1300C9BDB812367FF

To observe the seedfile string, use option -v. Notice that the seedfile string is 64 characters long and that spaces are
significant.

# rkey -D secret.key -v
89F96BC11480B0E1A37441397695E676 Qualcomm Atheros, Ocala FL [8@Z

The following command prints a new Network Membership Key (NMK) on stdout, instead of a DAK, using the seedfile
secret.key as the seed. Of course, one could specify another seedfile.

# rkey -M secret.key
B59319D7E8157BA001B018669CCEE30D

The following command prints 10 random SHA256 keys on stdout. SHA256 keys were printed because no other type of key was
specified. Program output could have been directed to a file or a pipe for further processing.

# rkey secret.key -n 10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The following three commands use the -o option to prevent the seedfile from being incremented before or after the key is
computed. Notice that a DAK is first generated then regenerated again. The third command generates an NMK using the
same seedfile value used to compute the previous two keys.

# rkey -D secret.key
B12E8BA7B0FF31D107BE15E96EF65B86
# rkey -oD secret.key
B12E8BA7B0FF31D107BE15E96EF65B86
# rkey -oM secret.key
FAD7EA3713497F2E134299FF1118F6B0

This utterly useless example demonstrates how to generate 10 identical device access keys by suppressing the normal
string increment between each key computation.

# rkey -oDn 10 secret.key
B12E8BA7B0FF31D107BE15E96EF65B86
B12E8BA7B0FF31D107BE15E96EF65B86
B12E8BA7B0FF31D107BE15E96EF65B86
B12E8BA7B0FF31D107BE15E96EF65B86
B12E8BA7B0FF31D107BE15E96EF65B86
B12E8BA7B0FF31D107BE15E96EF65B86
B12E8BA7B0FF31D107BE15E96EF65B86
B12E8BA7B0FF31D107BE15E96EF65B86
B12E8BA7B0FF31D107BE15E96EF65B86
B12E8BA7B0FF31D107BE15E96EF65B86

This example demonstrates how to assign distinct keys to script variables or insert them on a command line using this
program. Read the GNU bash manual for more information on shell scripting. See the modpib man page for an explanation
of program options shown.

# DAK=$(rkey -D secret.key)
# NMK=$(rkey -M secret.key)
# echo DAK=${DAK} NMK=${NMK}
# modpib -D $(rkey -D secret.key) -N ${NMK}

RECOMMENDATIONS
The seedfile is critical to the continuity and uniqueness of generated keys. The 64 character string stored in the seed‐
file is incremented, character by character, right to left, with each file access unless that behavior is suppressed
using the -o option. The SHA256 algorithm generates radially different output given minor changes in this string. The
key space is huge and the probability of collision is statistically small.

Be aware that two seedfiles containing the same start string will generate the same key sequence. To minimize the chance
of duplicate key values across production lines, each production line should use seedfiles having different start
strings. The length of the start string is not important but it should be different for each production line. If a
seedfile is lost, merely replace it with another one, as though you are opening another production line.

Mathematically, the shorter the start string the longer it will take for two different seedfiles to coincidentally pro‐
duce identical output. From 12 to 24 character is a reasonable length but this is not a restriction. If you have sev‐
eral production lines, you may want to maintain a record of the start strings used on each line in case a new seedfile
must be created.

REFERENCES
See the HomePlug AV Specification for more information on encryption keys, pass phrases and hash algorithms used and
standard FIPS180-2 sec 5.3.2 for more information on SHA256 encoding.

DISCLAIMER
Qualcomm Atheros reserves the right to modify program names, functionality, input format or output format in future tool‐
kit releases without any obligation to notify or compensate toolkit users.

SEE ALSO
hpavkey(1), hpavkeys(1), keys(1), mac2pw(1), mac2pwd(1)

CREDITS
Charles Maier <cmaier@qca.qualcomm.com> ]

open-plc-utils-0.0.3 Mar 2014 rkey(1)

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