SSL

SSL

İdris Yıldız

Mehmet Bilgin

05.04.2006

Outline

Public-Key Cryptography SSL SSL Security How to Make Your Application SSL Enabled Limitations of SSL Conclusion

Public-Key Cryptography

Conventional Cryptography– There is only one key both for encryption and decryption– The key must be known to both the sender and receiver

and the key must be secret– The key should be changed frequently

Public-key Cryptography– A pair of keys– One is used for encryption (private key) and the other is

used for decryption

Encryption

Sending a message using asymmetric keys1. Bob sends public key to Alice2. Alice encrypts message using Bob’s public key3. Alice sends encrypted message4. Bob decrypts message using his own private key

Alice Bob

Kpub

X = dKpr(Y)

Y = eKpub(X)

Y

1)

2)

3)

4)

Digital Signature

1. Bob encrypts the message with his private key2. Send encrypted message3. Alice decrypts message with Bob’s public key

Message is readable by ANYONE with Bob’s public key

Receiver can be confident that only someone with Bob’s privatekey could have sent the message

Alice Bob

Y

Y = eKpr(X)

X = dKpub(Y)

1)

2)

3)

Drawbacks of public-key encryption

It is slow– RSA is 1000 times slower than some conventional

encryption algorithms

Man-in-the-middle attack

Alice Bob

KPubB

X = dKPrB(Z)

Y = eKPubA(X)

Y

1)

2)

4)

5)

Attacker

KPubA

3)

Z = eKPubB(X)X = dKPrA(Y)

Z

SSL

Based on public key encryption 2 phases

– Handshake– Data Transfer

Runs above TCP/IP and below higher-level protocols

SSL Handshake Protocol

1) The client sends a message to the server that contains a list of the algorithms it is willing to use

2) The server chooses a algorithm out of the list and sends it back along with a certificate that containing the server’s public key

3) The client verifies the server’s certificate and extracts the server’s public key. Then generates a random key and encrypts it with the server’s public key. It sends this encrypted key to the user

4) The server takes the message and decrypts it with his private key

5) At last both the client and the server send a MAC message to each other to finish this handshake part

Authentication of a Server Certificate

X.509 Certificate

The certificate contains:– Your distinguished name– Your public key– The identity of the CA who issued the

certificate– Its expiry date– Digital signature of the CA which issued it

SSL Security

No good attacks are known on SSL There are some attacks explained in the

papers– Not have been used against production servers – It is not known that they are practical

Timing Cryptanalysis

Publicized by Paul Kocher in 1996 Based on the observation that cryptographic

operations take varying amount of time to complete depending on the keys that are being used

To overcome– add some random time to all operations – make all operations take constant time

Million Message Attack

Publicized by Daniel Bleichenbacher in 1998 By sending a series of chosen ciphertexts to

the server and observing the responses an attacker to get the session key

To overcome– make some small modification on the SSL

protocol

How to Make Your Web Application SSL(Https) Enabled ?

The Advantages of SSL for applications Generating Certificates with Java Configuring SSL in Tomcat Configuring SSL in OC4J (Oracle Containers

for Java)

The Advantages of SSL for applications

SSL with a certificate will provide the followings to your application:– The website (also customer) really is who it

claims to be– Credit card numbers, are encrypted and cannot

be intercepted– Data sent and received cannot be tampered or

forged

Generating Certificates with Java

A keystore (java.security.KeyStore) stores certificates

– An instance of java.security.KeyStore class– Stores certificates of all trusted parties– Authenticate parties by certificates in keystore

Create and manipulate a keystore using the keytool utility that is provided with the Sun Microsystems JDK

– keytool is in jdk_home/bin directory like javac– keytool -genkey -keyalg "RSA" -keystore “mykeys.store” -

storepass “mypass” -validity 365– “RSA” is the key generation algorithm– “mykeys.store” file is your certificate store– “mypass” is your secret key

Entering Certificate Info

Keytool will request certificate information after the creation command:

Configuring SSL in Tomcat

Providing SSL support is the job of Servers it is not related to the the application itself.

Application servers handles the https requests done to the applications

A cerftificate is needed (Assume we have created one, in mykeys.store)

– Copy the “mykeys.store” file to CATALINA_HOME/conf Define a SSL Connector on a port (Default port 443 requires to

be super user)– Add the following to CATALINA_HOME/conf/server.xml– <Connector port="8443"

      scheme="https" secure="true"      clientAuth="false" sslProtocol="TLS"       keystoreFile="/conf/ mykeys.store"      keypass=“mypass"/>

Configuring SSL in OC4J (Oracle Containers for Java)

The information will be valid for Standalone OC4J rather than Oracle Application Server

We will use the same key store for Tomcat and it should be copied to appropriate place

Create secure-web-site.xml – Copy http-web-site.xml and rename to secure-web-site.xml– Set protocol to https by setting secure element to true also specify

the https port (4443)– State the keystore that will be used : <ssl-config keystore="mykeys.store" keystore-password=“mypass"/>– Change server.xml and add the following to see your https

settings : <web-site path="./secure-web-site.xml" />

Limitations of SSL

Although SSL is widely it has some limitations SSL is designed to provide point-to-point security Incase of multiple intermediary nodes exist between the two

endpoints, point-to-point security fails and end-to-end security is required

– Web Service Scenario: SOAP messages route through multiple intermediary nodes, those intermediary nodes will not be able to participate to operations

SSL encryption is at the transport level rather than at the application.

– Messages are encrypted only during transmission over network

– Other security mechanisms are required to handle security of the messages in an application or disk

XML-based security schemas are being developed to eleminate the limitations of SSL

Questions?

THANKS A LOT !