One of reasons for shorter release cycles of the JDK is the ability to roll out faster security bug fixes and enhancements. In this article, we will review, in a nutshell, what are the major security enhancements introduced in latest JDK versions. As most of these enhancements are related to TLS, it is essential to understand the TLS handshake process as illustrated by the following diagram:

JDK 9

Major security enhancements introduced in JDK 9 are related to the TLS support provided by JSSE (Java Secure Socket Extension) API. These include:
• DTLS support in JDK 9: DTLS provides is essentially TLS over UDP so that you can encrypt communication established by unreliable protocols running over UDP:

SSLContext sslContext = SSLContext.getInstance("DTLS");
sslContext.init(…)
SSLEngine engine = sslContext.createSSLEngine();
engine.setUseClientMode(…); // true or false depending on whether it is a DTLS client or server

• TLS ALPN extension in JDK 9: provides support for negotiating the application protocol during the TLS handshake process; the list of acceptable protocols is set as a simple list of strings on both the TLS client and TLS server, as shown below:

SSLParameters sslParams = sslSocket.getSSLParameters();
sslParams.setApplicationProtocols(…)

or (for non-blocking mode of operation):

SSLParameters sslParams = sslEngine.getSSLParameters();
sslParams.setApplicationProtocols(…)

or (using more complex logic to determine the negotiated protocol):

sslSocket.setHandshakeApplicationProtocolSelector((serverSocket, clientProtocols) {
SSLSession handshakeSession = serverSocket.getHandshakeSession();
String cipher = handshakeSession.getCipherSuite();
int packetBufferSize = handshakeSession.getPacketBufferSize();
if("RC4".equals(cipher) && packetBufferSize > 1024) {
return "protocol1";
} else {
return "protocol2";
}
});

TLS ALPN comes in handy, i.e. for web servers that support both the HTTP 1.1 and HTTP 2.0 protocols over TLS for their clients
• OCSP Stapling for TCP: provides a mechanism for doing certificate revocation checking on the TLS server rather than the TLS client thus saving network bandwidth, must be enabled on both the TLS client and the TLS server:

-Djdk.tls.client.enableStatusRequestExtension=true
-Dcom.sun.net.ssl.checkRevocation=true

and (on the TLS server):

-Djdk.tls.server.enableStatusRequestExtension=true

• PKCS12 keystores, by default (so far these were JKS, but those are not portable across different than Java programming languages)
• DRBG-Based SecureRandom Implementations
• Utilization of CPU Instructions for GHASH and RSA
• SHA-1 Certificates disabled for certificate validation
• Implementation of the SHA-3 hash algorithms

JDK 10

There are two main enhancements introduced in JDK 10:

JEP 319 Root Certificates: a list or root certificates has been exposed to the cacerts keystore of the JDK
Some security-related APIs marked for removal: some

JDK 11

The major security enhancement introduced in JDK 11 is provided by JEP 332: Transport Layer Security (TLS) 1.3. This is the new version of the TLS protocol that provides a number of enhancements over the previous (1.2) version of the TLS specification. In addition, more enhancements are made to the root certificates in the cacerts keystore (some root certificates are added and some removed).