encode_keychange - produce the KeyChange string for SNMPv3
-t md5|sha1 [ OPTIONS
produces a KeyChange string using the old and new
passphrases as described in Section 5 of RFC 2274 "User-based Security
Model (USM) for version 3 of the Simple Network Management Protocol
option is mandatory and specifies the hash transform
type to use.
The transform is used to convert passphrase to master key for a given user (Ku),
convert master key to the localized key (Kul), and to hash the old Kul with
the random bits.
Passphrases are obtained by examining a number of sources until success (in
- command line options (see -N and -O options
- the file $HOME/.snmp/passphrase.ek which should only
contain two lines with old and new passphrase;
- standard input -or- user input from the
- -E [0x]<engineID> EngineID used for Kul
- <engineID> is intepreted as a hex string when
preceded by 0x, otherwise it is treated as a text string. If no <
engineID> is specified, it is constructed from the first IP
address for the local host.
- Force passphrases to be read from standard input.
- Display the help message.
- -N "<new_passphrase>"
- Passphrase used to generate the new Ku.
- -O "<old_passphrase>"
- Passphrase used to generate the old Ku.
- Turn off the prompt for passphrases when getting data from
- Be verbose.
- Echo passphrases to terminal.
The localized key method is defined in RFC 2274, Sections 2.6 and A.2, and
originally documented in
- U. Blumenthal, N. C. Hien, B. Wijnen, "Key Derivation
for Network Management Applications", IEEE Network Magazine,
April/May issue, 1997.