# phpman > man > encode_keychange(1)

[encode_keychange(1)](https://www.chedong.com/phpMan.php/man/encodekeychange/1/markdown)                           Net-SNMP                           [encode_keychange(1)](https://www.chedong.com/phpMan.php/man/encodekeychange/1/markdown)



## NAME
       encode_keychange - produce the KeyChange string for SNMPv3

## SYNOPSIS
       **encode**___**keychange** -t md5|sha1 [_OPTIONS_]

## DESCRIPTION
       **encode**___**keychange**  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  (SNMPv3)". **-t** 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 mas‐
       ter 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 order listed):

              command line options (see **-N** and **-O** options below);

              the  file  **$HOME/.snmp/passphrase.ek**  which should only contain two lines with old and
              new passphrase;

              standard input **-or-**  user input from the terminal.

## OPTIONS
### -E
              <_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.

### -f

### -h

### -N
              Passphrase used to generate the new Ku.

### -O
              Passphrase used to generate the old Ku.

### -P

### -v

### -V

## SEE ALSO
       The localized key method is defined in RFC 2274, Sections 2.6 and A.2, and  originally  docu‐
       mented in

              U.  Blumenthal, N. C. Hien, B. Wijnen, "Key Derivation for Network Management Applica‐
              tions", IEEE Network Magazine, April/May issue, 1997.



V5.9.1                                       16 Nov 2006                         [encode_keychange(1)](https://www.chedong.com/phpMan.php/man/encodekeychange/1/markdown)