SSL

1
SSL

• Idris Yildiz
• Mehmet Bilgin

05.04.2006
2
Outline

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

3
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

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Encryption

• Sending a message using asymmetric keys
• Bob sends public key to Alice
• Alice encrypts message using Bobs public key
• Alice sends encrypted message
• Bob decrypts message using his own private key

Alice
Bob
Kpub
1)
2)
Y eKpub(X)
Y
3)
4)
X dKpr(Y)
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Digital Signature

• Bob encrypts the message with his private key
• Send encrypted message
• Alice decrypts message with Bobs public key
• Message is readable by ANYONE with Bobs public
  key
• Receiver can be confident that only someone with
  Bobs private
• key could have sent the message

Alice
Bob
1)
Y eKpr(X)
Y
2)
X dKpub(Y)
3)
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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
Attacker
KPubB
KPubA
1)
2)
Y eKPubA(X)
Y
3)
Z eKPubB(X)
X dKPrA(Y)
4)
Z
5)
X dKPrB(Z)
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SSL

• Based on public key encryption
• 2 phases
• Handshake
• Data Transfer
• Runs above TCP/IP and below higher-level
  protocols

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SSL Handshake Protocol

• The client sends a message to the server that
  contains a list of the algorithms it is willing
  to use
• The server chooses a algorithm out of the list
  and sends it back along with a certificate that
  containing the servers public key
• The client verifies the servers certificate and
  extracts the servers public key. Then generates
  a random key and encrypts it with the servers
  public key. It sends this encrypted key to the
  user
• The server takes the message and decrypts it with
  his private key
• At last both the client and the server send a MAC
  message to each other to finish this handshake
  part

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Authentication of a Server Certificate
10
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

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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

12
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

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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

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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)

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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

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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

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Entering Certificate Info

• Keytool will request certificate information
  after the creation command

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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
  
• ltConnector port"8443"       scheme"https"
  secure"true"      clientAuth"false"
  sslProtocol"TLS"       keystoreFile"/conf/
  mykeys.store"      keypassmypass"/gt

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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
• ltssl-config keystore"mykeys.store"
  keystore-passwordmypass"/gt
• Change server.xml and add the following to see
  your https settings ltweb-site
  path"./secure-web-site.xml" /gt

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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

21
Questions?

• THANKS A LOT !