Encrypt Weblogic boot.properties using weblogic.security.Encrypt

# directory must be created for managed servers because it does not exist yet
mkdir -p ${DOMAIN_HOME}/servers/${SERVER_NAME}/security

echo "username=${ADMIN_USER}\npassword=\c" > ${DOMAIN_HOME}/servers/${SERVER_NAME}/security/boot.properties

${JAVA_HOME=}/bin/java -Dweblogic.RootDirectory=${DOMAIN_HOME} weblogic.security.Encrypt ${ADMIN_PASSWORD} >> ${DOMAIN_HOME}/servers/${SERVER_NAME}/security/boot.properties

weblogic.security.Encrypt documentation
http://download.oracle.com/docs/cd/E13222_01/wls/docs81/admin_ref/utils17.html