Configure the private keys for the signature in the file directory-rest.xml :
<filters>
<filter>
<filter-name>DocumentRestSecurity</filter-name>
<url-pattern>/rest/document/*</url-pattern>
<filter-class>fr.paris.lutece.util.signrequest.servlet.HeaderHashRequestFilter</filter-class>
<init-param>
<param-name>elementsSignature</param-name>
<param-value></param-value>
</init-param>
<init-param>
<param-name>validityTimePeriod</param-name>
<param-value>0</param-value>
</init-param>
<init-param>
<param-name>privateKey</param-name>
<param-value>changMe</param-value>
</init-param>
</filter>
</filters>