Jsse

Using JSSE for secure socket
communication
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Table of Contents
If you're viewing this document online, you can click any of the topics below to link directly to that section.

1. About this tutorial....................................................... 2
2. The Java Cryptography Architecture................................ 4
3. Whiteboard: An example application................................ 7
4. Key management ...................................................... 11
5. Using JSSE sockets ................................................... 15
6. Wrapup and resources ................................................ 20

Using JSSE for secure socket communication Page 1 of 22

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Section 1. About this tutorial
What is this tutorial about?
This tutorial explains the use of the Java Secure Socket Extension (JSSE) packages included
in JDK 1.4. The complexity of using JSSE is not in the communication itself, but rather in the
configuration. Before you can run your client/server software, you must create the keys needed
by the encryption algorithms, and these keys must be properly loaded by your software before
it can create secure sockets.

This tutorial provides cookbook-style instructions for creating and installing JSSE encryption
keys in a client/server application environment. When you have completed this tutorial, you will
know how to easily convert any existing client/server application to use encryption, as well as
how to create a secure application from scratch.

Prerequisites
To follow the discussion in this tutorial, you need to know a few things about the Java
language, starting with the basics of Java programming in a client/server environment (that is,
working with classes, objects, threads, and so on). Because stream and socket communication
is central to our discussion, you need to know how to use streams and sockets. In particular,
you should know what a stream is and what it is used for. You should know how to create a
Socket and a ServerSocket, how to get streams from each, and how to communicate using
those streams. You also should know how to create and compile a .java file using the JDK or
an IDE.

Two developerWorks tutorials, "Java sockets 101" and "Introduction to Java I/O," both
accessible from Resources on page 20 , provide useful background information.

You do not need to know anything about encryption technology to complete this tutorial. While
a comprehensive overview of encryption is beyond the scope of the discussion here, you will
be given the information you need to create secure client/server connections within your
applications.

Installation requirements
To run the examples in this tutorial, you need the following tools and components:

• JDK 1.4 from Sun Microsystems
• A development environment -- either an IDE or a suitable command-shell
• A computer on which you can run an Internet server

See Resources on page 20 to download the JDK 1.4 and complete source files necessary for
the completion of this tutorial.

Page 2 of 22 Using JSSE for secure socket communication

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About the author
Greg Travis is a freelance programmer living in New York City. His interest in computers can
probably be traced back to that episode of The Bionic Woman where Jamie runs around trying
to escape a building whose lights and doors are controlled by an evil artificial intelligence that
mocks her through loudspeakers. Greg is a devout believer in the idea that, when a computer
program works, it's a complete coincidence. He can be reached at mito@panix.com.



Section 2. The Java Cryptography Architecture
Overview
The Java platform's security and encryption features have grown tremendously over the last
few years. The JDK 1.4 (a.k.a. Merlin) release now comes bundled with many security-related
packages, including the Java Cryptography Extension (JCE), the Java Secure Socket
Extension (JSSE), and the Java Authentication and Authorization Service (JAAS). All of these
components are pieces of the Java Cryptography Architecture (JCA), as illustrated in the figure
below:

In this tutorial we'll mostly be working with the JSSE component of the JCA.

The JCA and JSSE
One of the most important features of JCA is that it doesn't rely on any one particular
encryption algorithm. Each well-known encryption algorithm has its advantages and
disadvantages, and new ones are being developed all the time. The JCA allows new
algorithms to be plugged in as they are developed. It uses the concept of the cryptographic
service provider (CSP), which is something like a security plug-in. A CSP supplies the
implementation of a particular algorithm. JDK 1.4 comes bundled with CSPs, including the
SunJSSE, that provide many standard algorithms; altogether, these are sufficient for most
uses.

JSSE provides secure socket communication for the Java 2 platform. More precisely, it
implements Secure Socket Layer (SSL) and Transport Layer Security (TLS), two standardized
protocols for implementing secure communications over the Internet. Both SSL and TLS rely
on public-key cryptography , which is described in the next panel.

Public-key cryptography



One problem with many cryptographic algorithms is that they require the distribution of shared
keys. A password is a good example of a shared key. The problem with shared keys is that
they must be shared between communicating entities before secure communication can start.
The sharing process, however, can be vulnerable to eavesdropping, which leads to a
chicken-and-egg problem: before we can exchange data securely, we must first exchange
secret keys securely.

This problem was solved in 1976 by Whitfield Diffie and Martin Hellman, with the creation of
public key cryptography. In the Diffie-Hellman public-key system each communicating party
holds a pair of keys -- one public and one private. The private key is known only to the
communicating party, while the public key can be given to anyone. Data encrypted using one
of the keys can only be decrypted with the other.

Thus, if you want to create a message to be read only by a particular party, you use their
public key to make the encryption, and they then use their private key to decrypt the message.

Likewise, if you encrypt a message with your private key, then anyone who has a copy of your
public key can use it to decrypt the message. This assures the person on the receiving end
that the message came from you and not someone else, since only you have your private key.
A message that you have encrypted in this way bears your digital signature.

Certificates and certificate authority
A certificate is a public key that has been digitally signed by a trusted party in order to prove
that it is a valid public key. This trusted party is called a certification authority (CA). In a sense,
the CA provides a testimonial that the public key really does belong to the person who owns it.

You can use commercial CAs for a fee, or you can create your own -- it all depends on how
much authority you want to wield when proving your identity in the digital realm. If an entity
signs its own public key, it's called a self-signed certificate . We use self-signed certificates
throughout this tutorial.

SSL and TLS
As previously mentioned, the JSSE framework, along with the SunJSSE provider, implements
the SSL and TLS protocol suites -- TLS being really just the newest version of SSL.

SSL uses public-key cryptography to exchange a set of shared keys, and then uses standard
shared-key encryption to exchange data. The shared keys are used both for encrypting the
data (making it unreadable by others) and for authenticating the data (ensuring that it hasn't
come from an impostor).

The SSL handshake protocol



Before data can be sent across an SSL connection, the two ends must negotiate and
exchange key information. This is called the handshake protocol. We won't go into much detail
about the handshake protocol here, because it isn't necessary for our purposes. For our
purposes, you need to know that the handshake involves the following steps:

1. The server sends its certificate to the client and the client verifies the server certificate.

2. The client sends its certificate to the server and the server verifies the client certificate.

3. The client encrypts password information with the server's public key and sends it to the
server. This password information is used by each end of the connection to generate
identical secret keys, which will then be used to transmit data.

Client authentication (Step 2) is optional: the server can request that the client provide its
certificate, but it is not required to make such a request. We will be using client authentication
in our example.

Now that you have a basic understanding of the infrastructure of JCA and JSSE under your
belt, we can move on to the more active part of the tutorial: working with a live example.



Section 3. Whiteboard: An example application
Overview
To demonstrate how JSSE works in the real world, we're going to employ a simple distributed
whiteboard system. The whiteboard is a program that lets users write text messages onto a
blank canvas. These text messages then appear on the canvases of other users who are
connected to the same whiteboard server. This allows people in different locations to
communicate.

Because we're more interested in the security aspects of this program than in the whiteboard
functionality itself, we'll keep the application very simple. Our whiteboard will allow users to
create text messages, but it will not allow them to delete messages. Mostly, we'll just pay
attention to how the whiteboard implements JSSE, thus ensuring that messages can be
securely sent between users.

In this section we discuss the basic structure of the whiteboard and how it implements JSSE.
In the next section, we'll begin working directly with the code for the whiteboard application.

Using the whiteboard
The figure below illustrates the simple whiteboard we'll be working with. Each client's
messages are shown in a different color.

The distributed whiteboard showing messages sent by different users

In the following two figures, you see two whiteboard client windows. Imagine that each of these
windows is running on a different machine. The first user has clicked somewhere in his window
and typed a message, but he has not yet pressed Return.



The first user is typing a message and has not yet The second user therefore has not received a
pressed return. yet.

Now, imagine the first user presses Return, which causes his message to show up in the
window of the second user. The second user then sends a response, as illustrated in the two
figures below.

The first user has pressed return and sent a message, The second user received the first user's mess
and then received a response from the second user. and then sent a response.

Each user sees his own text in black; other users' text appears in different colors assigned by
the server.

The client/server structure



On the server side of the whiteboard application, we have a class called Server. This class
listens for incoming connections on a specified port. Each time a connection comes in, the
Server creates a ConnectionProcessor to process the connection. Processing a
connection means receiving text messages and sending them back out to other clients. The
Server gives each client one ConnectionProcessor.

When a client first starts up, it initiates a connection to the server. The client keeps this
connection open throughout the whiteboard session. Each text message is sent along this
connection.

The figure below illustrates the client/server processes for the whiteboard application.

Key files
As we already discussed, the whiteboard uses JSSE, and JSSE implements the SSL and TLS
protocols. These protocols use public-key encryption to ensure the privacy of messages sent
over the Internet. In a public-key encryption system, both clients and server must have a pair
of keys, one public and one private. Before our whiteboard can even begin to mediate
messages between users, we must generate these keys.

Once the keys have been generated, we'll provide the client side a file containing its public and
private keys. It will also have a copy of the server's public key certificate. Keys are stored in a
specially formatted file called a keystore.

The following table describes the keystore files we'll be using.

Keystore file What it contains Where it goes
client.private The client's public/private key pair Client side
server.public The server's public key certificate Client side
server.private The server's public/private key pair Server side



client.public The client public key certificate Server side

Key protection
The server also has a file containing its own public and private keys, as well as the client's
public key certificate. Recall that public keys can be given out freely -- there's no need to hide
them from any other party.

It is important that each end of the client/server connection has only the key files it needs to
work properly. In particular, it's important that only the server has a copy of its own private key.
In the wrong hands, this key could do much damage, since it would essentially allow a
malicious entity to cloak itself under the server's identity.

Now that you have an idea of how the whiteboard is put together, we can begin working more
directly with each of its components. In the next section, you'll learn how to generate and
manage public/private key pairs in a client/server system.



Section 4. Key management
Overview
Key generation and manipulation is performed with the keytool program, which is included with
the JSSE packages in JDK 1.4. keytool can be used for a variety of purposes. Here, we'll be
using it to create public/private key pairs, and to extract the public key certificates from these
pairs and place them in their own files.

Generating a key pair
The following keytool command is used to generate a new public/private key pair:

keytool -genkey -keystore [filename]

When you run this command, you will be asked a series of questions. These questions
concern you as an entity (your name, organization, and the like). The information you provide
will be used to create a self-signed certificate that associates the information with a public key
and testifies to the authenticity of the association. You will also be asked to enter passwords
for the keystore and, optionally, passwords for the key pair you are creating.

Working from the command line
Below is a complete command that generates a public/private key pair and specifies all the
required entity information without asking you any questions about your identity; that
information is provided directly on the command line. The table that follows explains each
option in the command.

keytool -genkey -alias clientprivate -keystore client.private
-storetype JKS -keyalg rsa -dname "CN=Your Name, OU=Your
Organizational Unit, O=Your Organization, L=Your City, S=Your State,
C=Your Country" -storepass clientpw -keypass clientpw

Option What it means
-genkey Tells keytool to generate a key pair.
-alias clientprivate Identifies the new key pair within the keystore.
-keystore client.private Uses the file client.private as the keystore.
-storetype JKS Declares the type of the keystore. JKS is the default.
-keyalg rsa Declares the algorithm to be used; we're using the RSA public key
algorithm, which is the default.
-dname "CN=Your Name..." Provides information about the entity owning the key pair.



-storepass clientpw Specifies the password for the entire keystore.
-keypass clientpw Specifies the password for the new key pair.

Client and server key pairs
The first step in the preparation of our algorithm is to generate a public/private key pair for the
client and another pair for the server. The following command will generate the file
client.private, which is the key pair for the client:

keytool -genkey -alias clientprivate -keystore client.private
C=Your Country" -storepass clientpw -keypass clientpw

And here is the command to generate the file server.private, which is the key pair for the
server:

keytool -genkey -alias serverprivate -keystore server.private
C=Your Country" -storepass serverpw -keypass serverpw

As mentioned in the panel Key files on page 9 , the private client and server key files need to
be installed in specific places. The client.private file is installed on the client side; the
server.private file is installed on the server side.

Extracting public keys
The next step is to extract the public keys so they can be installed with the client and server.
Specifically, the client-side software must have the public key of the server side, and vice
versa.

To get the public keys, we extract them from the client.private and server.private files and
place them in temporary files. Then, we insert them into their own keystores, called
client.public and server.public, respectively.

The temporary key file, temp.key, is used to hold each of the public keys, temporarily, while it
is being copied from the private keystore to the public keystore -- for example, from
client.private to client.public. After completing the export/import procedure, you'll want to
remove the temp.key from the current directory.

Export/import commands



We'll use the keytool -export command to extract the public key into a file, and then use
the keytool -import command to insert it into a new keystore. Here's the command to
extract the client's public key:

keytool -export -alias clientprivate -keystore client.private -file
temp.key -storepass clientpw

And here's the command to insert the client's private key into its own keystore:

keytool -import -noprompt -alias clientpublic -keystore client.public
-file temp.key -storepass public

We'll also extract and store the server's public key. Here's the command to extract the key:

keytool -export -alias serverprivate -keystore server.private -file
temp.key -storepass serverpw

And here's the command to place it in its own keystore:

keytool -import -noprompt -alias serverpublic -keystore server.public
-file temp.key -storepass public

The script generatekeys.sh (for UNIX) and generatekeys.bat (for DOS or Microsoft Windows)
automatically generates the client and server key files for you and cleans up any temporary
files. See Resources on page 20 to download the script.

Installing the files
Before we move on to the next section, it's important to make sure that the key files are
installed properly on the client and server ends. The following files should be installed on the
client side:

• Client.class
• Client$1.class
• Client$2.class
• Client$ClientCanvas.class
• Posting.class
• client.private
• server.public

And these files should be installed on the server side:

• Server.class



• Posting.class
• ConnectionProcessor.class
• client.public
• server.private

With the public/private key pairs properly installed on our client and server systems, we're
ready to begin using the whiteboard application to exchange messages. In the next section,
we'll examine the code for the whiteboard application itself.



Section 5. Using JSSE sockets
Overview
Our whiteboard is a client/server application that uses sockets to communicate with the server.
Because we want our communications to be private, we'll be using JSSE secure sockets
instead of regular sockets. Secure sockets are used the same way that regular sockets are,
except that they transparently encrypt any data that passes through them.

Before we get into how JSSE creates and manages secure connections, we should review
how regular, nonsecure connections are initiated and accepted.

Nonsecure sockets: A review
The following code fragment is typical for initiating a socket connection. This example creates
a new Socket connection to port port at the remote computer host:

Socket socket = new Socket( host, port );

Similarly, the following code demonstrates how we listen for incoming connections. This
example creates a ServerSocket listening on port port, and then enters an infinite loop,
accepting and processing incoming connections:

ServerSocket serverSocket = new ServerSocket( port );
while (true) {
Socket socket = serverSocket.accept();
doSomethingWithNewConnection( socket );
}

Secure sockets work in a very similar manner, but before we can implement them for our
example we must complete several steps. We'll go over these steps in the panels that follow.

Connection setup
To initiate a secure socket connection to a remote server, we must carry out the following
steps:

1. Create a SecureRandom, a source of secure random numbers. Secure random numbers
are numbers that are random enough that they will not make the encryption vulnerable to
attack.

2. Create a KeyStore object containing the remote server's public key. This is read from
server.public.



3. Create a KeyStore object containing the client's public/private key pair, including its public
key certificate. This is read from client.private.

4. Create a TrustManagerFactory from the remote server's KeyStore. This is used to
authenticate the remote server.

5. Create a KeyManagerFactory from the client's KeyStore. This is used for encrypting and
decrypting data.

6. Create an SSLContext object, using the KeyManagerFactory, the
TrustManagerFactory, and the SecureRandom.

7. Use the SSLContext to create an SSLSocketFactory.

8. Use the SSLSocketFactory to create an SSLSocket, which acts just like a regular
Socket, except that it is secure.

Listening setup
To listen for incoming connections, we must carry out a similar set of steps:

1. Create a SecureRandom, a source of secure random numbers.

2. Create a KeyStore object containing the remote client's public key. This is read from
client.public.

3. Create a KeyStore object containing the server's public/private key pair, including its public
key certificate. This is read from server.private.

4. Create a TrustManagerFactory from the remote client's KeyStore. This is used to
authenticate the remote client.

5. Create a KeyManagerFactory from the server's KeyStore. This is used for encrypting
and decrypting data.

6. Create an SSLContext object, using the KeyManagerFactory, the
TrustManagerFactory, and the SecureRandom.

7. Use the SSLContext to create an SSLServerSocketFactory.

8. Use the SSLServerSocketFactory to create an SSLServerSocket, which acts just like



a regular ServerSocket, except that it is secure.

9. Call the accept() method of the SSLServerSocket to wait for an incoming connection.

It's all pretty complicated, but the process is the same each time, so it makes sense to follow
along and see how it all works. In the panels that follow, we'll walk through the code that
carries out these steps. We'll examine only the client-side process in detail, because the
server-side process is nearly the same. Afterwards, we'll note the differences between the two
sides.

Creating a SecureRandom
Creating a SecureRandom object is easy; just use the following lines in your code:

secureRandom = new SecureRandom();
secureRandom.nextInt();

The first line actually creates the SecureRandom. Creating a SecureRandom takes a lot of
computation, and this computation may not be executed until it's actually used. By calling the
nextInt() method here, we get the creation process going and ensure the delay will happen
at the start of the program, not later when it might inconvenience us.

Creating keystores
Next, we need to create some KeyStore objects. We create an empty KeyStore using the
static method KeyStore.getInstance(), and initialize it using its load() method, as
illustrated below:

private void setupServerKeystore()
throws GeneralSecurityException, IOException {
serverKeyStore = KeyStore.getInstance( "JKS" );
serverKeyStore.load( new FileInputStream( "server.public" ),
passphrase.toCharArray() );
}

Note that we've created a KeyStore of type "JKS"; this is the standard keystore format used
in JCA.

Reading keystores
In the previous panel, we read the key information from server.public, which contains the
server side's public key. We also need to read the client key pair from client.private, as shown
here:



private void setupClientKeyStore()
throws GeneralSecurityException, IOException {
clientKeyStore = KeyStore.getInstance( "JKS" );
clientKeyStore.load( new FileInputStream( "client.private" ),
"public".toCharArray() );
}

Setting up factories
The next step is to use the KeyStore objects we've created to initialize key and trust manager
factories. We'll create a TrustManagerFactory from the server keystore; this will be used to
authenticate (that is, begin to trust) the remote server:

TrustManagerFactory tmf = TrustManagerFactory.getInstance( "SunX509" );
tmf.init( serverKeyStore );

Note that the TrustManagerFactory is of type "SunX509"; 509 is the name of the
certification protocol we're using throughout this program. In the second code line, the
TrustManagerFactory is loaded with the server's keystore.

We must also create a KeyManagerFactory from the client's KeyStore, as shown below:

KeyManagerFactory kmf = KeyManagerFactory.getInstance( "SunX509" );
kmf.init( clientKeyStore, passphrase.toCharArray() );

Creating an SSLContext
We're getting close to finalizing our secure socket setup, so stay with me! The next step is to
create an SSLContext. An SSLContext contains all the key and certificate information we've
mentioned so far, and is used to create an SSLSocketFactory, which in turn creates secure
sockets.

Once you've created an SSLContext at the start of an application, you can use it for each
connection you need to make, as long as each connection uses the same keys.

To create an SSLContext, we use our factories and the SecureRandom, as shown here:

sslContext = SSLContext.getInstance( "TLS" );
sslContext.init( kmf.getKeyManagers(),
tmf.getTrustManagers(),
secureRandom );

Note that we've created an SSLContext of type "TLS". As you suspect, this stands for
Transport Layer Security, which is the new name for the Secure Sockets Layer, or SSL. We
then initialize it with the TrustManagerFactory and KeyManagerFactory objects we



created a few steps back.

Establishing a connection
We're at the last step. All the work we've done so far has given us an SSLContext, which
we're going to use to make a connection to a remote machine, as shown in the code sample
below:

SSLSocketFactory sf = sslContext.getSocketFactory();
SSLSocket socket = (SSLSocket)sf.createSocket( host, port );

We've just made a secure connection to port port on the machine host.

Server-side setup
Setting up the server side is more or less the same as setting up the client side, so we won't go
over it in detail. Of course, the server reads its key information from client.public and
server.private, rather than from server.public and client.private.

In addition, the code to carry out the final step (establishing a connection) is a little different for
the server side, as shown here:

SSLServerSocketFactory sf = sslContext.getServerSocketFactory();
SSLServerSocket ss = (SSLServerSocket)sf.createServerSocket( port );
ss.setNeedClientAuth( true );

Note that we called SSLServerSocket.setNeedClientAuth(). This is the server call
indicating that the client should authenticate itself. Client applications do not authenticate
themselves by default, so you must make this call if you want client authentication to be part of
the handshaking process.



Section 6. Wrapup and resources
Tying it all together
In this tutorial we've focused on the most complex aspect of using JSSE: properly configuring
and installing the client and server key pairs. We talked briefly about the new Java
Cryptography Architecture, but mostly focused on the use of key pairs for secure encryption,
as implemented by JSSE. We used a very simple whiteboard example to make the discussion
in the tutorial more concrete, going over each step necessary to generate key pairs, properly
install them, and initiate a secure, socket-based client/server connection.

You can find the complete code source for the whiteboard example in Resources on page 20 .
Build on what you've learned here by studying that code source and paying close attention to
the steps outlined in the previous section. You may also want to practice what you've learned,
and expand upon it, with the suggested exercise in the next panel. Whatever you do, be sure
to use what you've learned here when it comes time to develop your next secure socket-based
application.

Further exercises: Using a CA
In our whiteboard example, we've assumed that you have control over both the client-side and
server-side installations. In other configurations, this isn't the case. For example, Web servers
can be used with just about any Web browser, and the people who install the Web server
software have nothing to do with those who install browser software. For this reason, Web
servers and other public-protocol servers use third-party certification authorities to provide key
certificates.

Instruction for using these systems is beyond the scope of this tutorial, but each one generally
provides its own detailed instructions. In many cases, you can request a free certificate which
can be used for testing purposes -- this lets you "try before you buy." See Resources on page 20
for links to third-party certification authorities.

Resources
• Download jsse-source.zip, the code source for the examples and scripts used in this tutorial.

• Download the JDK 1.4 (http://java.sun.com/j2se/1.4/download.html) from Sun Microsystems.

• Read the installation instructions for JSSE 1.0.2
(http://java.sun.com/products/jsse/INSTALL.html), an extension to the Java 2 platform.

• The Sans Institute offers a good introduction to the history of public-key (Diffie-Hellman)
cryptography (http://rr.sans.org/encryption/diffie.php).



• The IEEE maintains a page documenting specifications for public-key cryptography
(http://grouper.ieee.org/groups/1363/).

• Verisign, an IBM affiliate, is a major third-party provider of SSL certificates
(http://www.verisign.com/products/site/index.html).

• Thawte, another major provider of SSL certificates, will let you try before you buy
(http://www.thawte.com/).

• Sun Microsystems's Security enhancements for the Java 2 SDK, Standard Edition v1.4
(http://java.sun.com/j2se/1.4/docs/guide/security/) describes the security features included in
JDK 1.4.

• Read Sun's guide to the Java Cryptography Extension (http://java.sun.com/products/jce/) to
find out more about JCE.

• The Java Secure Socket Extension (JSSE) Reference Guide
(http://java.sun.com/j2se/1.4/docs/guide/security/jsse/JSSERefGuide.html) provides a
comprehensive guide to JSSE.

• For more hands-on learning about sockets programming for the Java platform, take the
"Java sockets 101" tutorial by Roy Miller and Adam Williams (developerWorks, August 2001,
http://www-106.ibm.com/developerworks/education/r-jsock.html).

• For details on streams, check out the tutorial Introduction to Java I/O by IBM Learning
Services (developerWorks, April 2000,
http://www-106.ibm.com/developerworks/education/r-jio.html). Note that this tutorial is not
based on Java 1.4.

• The JDK 1.4 tutorial, also by Greg Travis, includes a chapter on JSSE (Manning
Publications, May 2002,
http://www.amazon.com/exec/obidos/ASIN/1930110456/103-2127487-6951840).

• To learn more about socket programming, read Java Network Programming : A Complete
Guide to Networking, Streams, and Distributed Computing, by Merlin Hughes, Michael
Shoffner, Derek Hamner, and Conrad Hughes (Manning Publications, 1999,
http://www.amazon.com/exec/obidos/ASIN/188477749X/qid=1016060142/sr=8-1/
ref=sr_8_71_1/103-2127487-6951840).

• Another good resource for learning about socket programming and security is Java Network
Programming, by Elliotte Rusty Harold (O'Reilly and Associates, 2000,



• If you need to learn more about security on the Java 2 platform, see Professional Java
Security, by Jess Garms and Daniel Somerfield (Wrox Press, 2001,

• The whitepaper "Security in a Web services world" (developerWorks, April 2002,
http://www-106.ibm.com/developerworks/library/ws-secmap/) discusses the new joint
IBM-Microsoft proposal for integrated, standardized security on Web services architectures;
the proposal includes a provision for the use of public-key technology.

• The IBM Zurich Research Lab (http://www.zurich.ibm.com/csc/infosec/) has a long history in
the study and implementation of security systems, especially in the area of cryptography.

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