There is a requirement to enable the JMX authentication of Cassandra. The steps followed are as follows:

1. cd /home/user1/janusgraph-full-0.5.2/conf/cassandra

2. vi cassandra-env.sh

3. original : 

LOCAL_JMX=yes

if [ "$LOCAL_JMX" = "yes" ]; then
  JVM_OPTS="$JVM_OPTS -Dcassandra.jmx.local.port=$JMX_PORT -XX:+DisableExplicitGC"
else
  JVM_OPTS="$JVM_OPTS -Dcom.sun.management.jmxremote.port=$JMX_PORT"
  JVM_OPTS="$JVM_OPTS -Dcom.sun.management.jmxremote.rmi.port=$JMX_PORT"
  JVM_OPTS="$JVM_OPTS -Dcom.sun.management.jmxremote.ssl=false"
  JVM_OPTS="$JVM_OPTS -Dcom.sun.management.jmxremote.authenticate=true"
  JVM_OPTS="$JVM_OPTS -Dcom.sun.management.jmxremote.password.file=/etc/cassandra/jmxremote.password"
#  JVM_OPTS="$JVM_OPTS -Djavax.net.ssl.keyStore=/path/to/keystore"
#  JVM_OPTS="$JVM_OPTS -Djavax.net.ssl.keyStorePassword=<keystore-password>"
#  JVM_OPTS="$JVM_OPTS -Djavax.net.ssl.trustStore=/path/to/truststore"
#  JVM_OPTS="$JVM_OPTS -Djavax.net.ssl.trustStorePassword=<truststore-password>"
#  JVM_OPTS="$JVM_OPTS -Dcom.sun.management.jmxremote.ssl.need.client.auth=true"
#  JVM_OPTS="$JVM_OPTS -Dcom.sun.management.jmxremote.registry.ssl=true"
#  JVM_OPTS="$JVM_OPTS -Dcom.sun.management.jmxremote.ssl.enabled.protocols=<enabled-protocols>"
#  JVM_OPTS="$JVM_OPTS -Dcom.sun.management.jmxremote.ssl.enabled.cipher.suites=<enabled-cipher-suites>"
fi

Updated:

When I try to restart the service using command getting an error.

/home/user1/janusgraph-full-0.5.2/bin/janusgraph start

Forking Cassandra...
Running `nodetool statusthrift`........................ timeout exceeded (60 seconds)
See /home/fusionops/janusgraph-full-0.5.2/bin/../logs/cassandra.log for Cassandra log output.

bin/nodetool status

SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/fusionops/janusgraph-full-0.5.2/lib/slf4j-log4j12-1.7.12.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/fusionops/janusgraph-full-0.5.2/lib/logback-classic-1.1.3.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]
error: Authentication failed! Credentials required
-- StackTrace --
java.lang.SecurityException: Authentication failed! Credentials required
at com.sun.jmx.remote.security.JMXPluggableAuthenticator.authenticationFailure(JMXPluggableAuthenticator.java:211)
at com.sun.jmx.remote.security.JMXPluggableAuthenticator.authenticate(JMXPluggableAuthenticator.java:163)
at org.apache.cassandra.utils.JMXServerUtils$JMXPluggableAuthenticatorWrapper.authenticate(JMXServerUtils.java:279)
at javax.management.remote.rmi.RMIServerImpl.doNewClient(RMIServerImpl.java:232)
at javax.management.remote.rmi.RMIServerImpl.newClient(RMIServerImpl.java:199)
at javax.management.remote.rmi.RMIJRMPServerImpl$ExportedWrapper.newClient(RMIJRMPServerImpl.java:253)
at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:357)
at sun.rmi.transport.Transport$1.run(Transport.java:200)
at sun.rmi.transport.Transport$1.run(Transport.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:573)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:834)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:688)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:687)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:303)
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:279)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:164)
at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(RemoteObjectInvocationHandler.java:235)
at java.rmi.server.RemoteObjectInvocationHandler.invoke(RemoteObjectInvocationHandler.java:180)
at com.sun.proxy.$Proxy7.newClient(Unknown Source)
at javax.management.remote.rmi.RMIConnector.getConnection(RMIConnector.java:2430)
at javax.management.remote.rmi.RMIConnector.connect(RMIConnector.java:308)
at javax.management.remote.JMXConnectorFactory.connect(JMXConnectorFactory.java:270)
at org.apache.cassandra.tools.NodeProbe.connect(NodeProbe.java:183)
at org.apache.cassandra.tools.NodeProbe.<init>(NodeProbe.java:150)
at org.apache.cassandra.tools.NodeTool$NodeToolCmd.connect(NodeTool.java:302)
at org.apache.cassandra.tools.NodeTool$NodeToolCmd.run(NodeTool.java:242)
at org.apache.cassandra.tools.NodeTool.main(NodeTool.java:158)

Are there any other changes required ??

Thanks & Regards,

Vinayak