X.509 certificate (end of chapter 31)

1. Skip section 32.1 (IPSec and Virtual Private Network-VPN) – They require information on IP that I’ve not yet covered. • Possible paper topic • Will cover after TCP/IP, if time, but probably won’t have it.

2. X.509 certificate (end of chapter 31) • identifies a server site and verifies it is who it says it is. • It’s like an ID card stored electronically. • Used for Internet transactions as part of a security protocol • Issued by a trusted Certification Authority (CA) • Examples: thawte, verisign, entrust, godaddy.

3. EV (Extended validation) certificates • http://en.wikipedia.org/wiki/Extended_Validation_Certificate • I will not distinguish X.509 and EV but could be a paper topic that gets into more detail than I will

4. CA’s responsibilities • Verify the entity is who they say they are. • This is an investigative procedure into the entity requesting the certificate. • Create a certificate (and issue to the entity) to contain the following information:

5. Certificate • Contains: • Owner's public key (and algorithm) • Owner's name • Expiration date of the public key • Name of the issuer (the CA that issued the Digital Certificate) • Serial number of the Digital Certificate • Certificate thumbprint calculated with the CA’s private key. This establishes the authenticity of the certificate and guarantees the certificate cannot be tampered with • Version # • more

6. SSL/TLS – 32.2 • TCP establishes a connection between two sites. • SSL-Secure Sockets Layer • End-to-end security protocols • Authenticate server and client to each other • Message integrity • Originally designed by Netscape • Used by virtually every Internet commerce site

7. TLS-Transport Layer Security • TLS is the IETF version of SSL • Openssl. For those of you with Linux accounts – man openssl or man x509. • Won’t distinguish here but plenty of room for a paper topic.

8. Figure 32.14 Location of SSL and TLS in the Internet model

9. Possible sequence of steps for SSL is. • Client sends info to server • SSL or TLS version # • list of compression/encryption techniques • key exchange algorithms supported • session ID • random data.

10. Server sends info to client • what it supports and wants to use • random data • certificate • Both sides now know what the other can do.

11. Authenticate the server • Client verifies certificate it received from the server • Check certificate expiration date • Check certificate authority (is it in a list of trusted CAsmaintained by the client) • use CA’s public key and apply it to the digital signature (fingerprint, thumbprint) to get the digest value and authenticate – is this a valid certificate? • compare domain name in certificate w/ domain name of server (to prevent man-in-the-middle attack)

12. Client creates pre-master secret key and encrypts using server’s public key (obtained from the certificate); sends to server. Server gets it and decrypts using its private key. • Server may authenticate client. • Client and server feed random data from both sides and premaster secret into a hash algorithm to generate a session key. • Exchange information securely

13. Figure 32.15 Creation of cryptographic secrets in SSL

14. Some other references • [http://support.microsoft.com/kb/257591] • [http://msdn2.microsoft.com/en-us/library/aa380513.aspx] • [http://www.cisco.com/en/US/tech/tk583/tk618/tsd_technology_support_protocol_home.html]

15. You can see certificates • connect to an https site (e.g. www.bankmutual.com and select customer login) • Note the lock icon at the top next to the URL). • click on the icon and select view certificates and select various tabs and options. • DO NOT ASSUME sites are secure • Look for the lock icon or https as opposed to http in the URL.

16. To see trusted CAs: • Tools  Internet Options and select Content tab • Select Certificates button followed by one of the tabs. • Select a CA and click the View button. • Explore various tabs. • Book has a little more on SSL and TLS and could be used as part of a paper topic.

17. What if the certificate does not check out?

18. PGP (Pretty good Privacy) • In the early 1990s, encryption algorithms were in the same category as weapons and were declared as a munitions – making them subject to strict export laws. • PGP was developed by Phillip Zimmerman • Putting it on the Internet was akin to exporting it, according to the State dept. • Subject of a 3-year criminal investigation • Since then, export laws governing encryption have been relaxed. • Another reference at www.pgpi.org (trial versions used to be available but are hard to find now-at least for more recent OS’s)

19. Figure 32.19 Position of PGP in the TCP/IP protocol suite

20. Table 32.4 PGP Algorithms

21. Example use of PGP (run on an older environment)

22. When the message is open the receiver sees: ---BEGIN PGP SIGNED MESSAGE--- Hash: SHA1 this is a test message ---BEGIN PGP SIGNATURE--- Version: PGPfreeware 6.5.8 for non-commercial use <http://www.pgp.com> iQA/AwUBPVHAkz012x9/xPKqEQL7UQCg65yJ8I4c5o7s37iMvLcqqRtokhAAn3E2 EzQd3vhFE41QGj3O8zvDSawR =knKs ---END PGP SIGNATURE---

23. With the message open the user can select decrypt/verify from the PGP dropdown menu *** PGP Signature Status: good *** Signer: William Shay ,shayw@uwgb.edu. *** Signed: 8/7/02 7:51:31 PM *** Verified: 8/7/02 8:50:46 PM *** BEGIN PGP VERIFIED MESSAGE *** this is a test message *** END PGP VERIFIED MESSAGE ***

24. Textbook covers a bit more and gets into key rings and such. I will skip that but this a possible paper topic.

25. Firewalls. - 32.4 • Allows or disallows data to pass through. • How does it decide?

26. Packet filtering • IP packet format

27. May accept or reject a packet based on its IP address and/or port number • For example, the client/server project works, in theory, if one machine is on campus and the other is off. • It is, however, subject to firewall rules.

28. Examples • Disallow incoming packets with port # 23 (disables telnet). • Disallow outgoing packets with specified destination addresses. Could be used to restrict employees from access certain external sites (competitors or game playing sites) during work hours. • Example: Some businesses disallow employees to access youtube, facebook, or similar sites. • Disallow outgoing with specified source addresses (to prevent address spoofing – a form of attack discussed later)

29. Initial firewall setup. • Can allow all by default then specify which to reject • Runs the risk of missing something that should be rejected • Can reject all by default and then specify which to allow • Runs the risk of people getting PO’d if you miss an application that should pass

30. Possible policies: firewall setting (from Kurose & Ross) • No outside web access: Drop all outgoing packets to an IP address, port 80 (HTTP). • No incoming TCP connections, except those for organization's public Web server (130.207.244.203): Drop all incoming TCP SYN packets to any IP except 130.207.244.203, port 80. • Prevent web-radios from eating up the available bandwidth: Drop all incoming UDP packets – except DNS packets.

31. Prevent network from being used for a smurfDoS attack: drop all ICMP ping packets going to a broadcast address. • Prevent your network from being tracerouted: drop all outgoing ICMP TTL expired traffic.

32. Application level gateway (proxy server) • Packet filtering uses layer 3/4 information • Book example: • Only those Internet users who have previously established business relations with the company can have access to certain web pages. • Packet filtering won’t work • Cannot distinguish the above cases

33. Runs a program for each type of application • Intercepts all requests at a high layer and forwards (or rejects) them as needed. • More overhead than packet filtering (firewall must run duplicate apps) • Increased flexibility based on intent of applications

34. Stateful inspection (not in text) • Packets examined based on contents AND context (i.e. what has happened previously). • Admin defines a rule base that determines course of action. • Example: a ping packet sends an echo-request packet • Example: type ping url in a dos window – or in Linux • Could reject an echo-response packet if there was no previous echo-request packet in the other direction.

35. Deny an incoming acknowledgment to a request that never happened. • Client established a ftp connection and server attempts to initiate a file transfer before the client has requested it. Denied. • Maybe client tries to sneak a packet with a different port # through the existing connection. Denied.

36. Refs: • [http://en.wikipedia.org/wiki/Stateful_firewall] • [http://www.webopedia.com/TERM/S/stateful_inspection.html]

37. Can purchase different levels of firewall protection. • Can install on your machine. • Can specify which apps can access the Internet or which sources from the Internet can access your computer. • Administrator defines a rule base defining actions. • Firewalls can also restrict # packets per second (prevent student from setting up game servers on campus)

38. Attacks (not in text) – I will provide an overview only – a possible paper topic • Smurf (DoS) attack: • send a ping packet but falsify the source and use a broadcast address for the destination. • All nodes in the broadcast group reply to the “source” inundating it with traffic. • Presumably the attacker creates an infinite loop sending such packets. • [http://www.cert.org/advisories/CA-1998-01.html] • [http://en.wikipedia.org/wiki/Denial-of-service_attack]

40. SYN flood • send connection requests (with a false source) to a site. • Site waits for a confirmation and times out if it does not arrive. • If requests are sent faster than timeouts occur, problems occur. • [http://www.cert.org/advisories/CA-1996-21.html]

41. Slowloris attack • Utilizes legitimate HTTP traffic • Sends partial http requests • Sends additional information periodically to keep socket connections open • Ties up connections making them unavailable to legitimate use • Like SYN flood but over http • http://www.funtoo.org/en/security/slowloris/ and http://en.wikipedia.org/wiki/Slowloris

42. There are bad things are out there • Malware – a generic term covering a wide variety of bad things. • Virus – program attached to another that does unintended things • May be destructive • May not be (technically) • All are disruptive and cause loss or work or trust

43. Worm: a program that can invade a computer but is NOT attached to another program. • Might be running something that’s prone to accepting a worm from the internet and run it. • Might access your outlook contacts and send a copy of itself to everyone there. • Blaster worm: allow others to control your computer. • Trojan Horse: hidden part of other useful program • Typically doesn’t replicate like worms and viruses • Summary

44. Packet sniffer: • records copies of packets that it sees • A good reason to secure wireless connections • Spyware: • watch what you do and perhaps report it to someone else. • You may be completely unaware • Botnet: • collection of computers working together for a purpose

45. Clipper Chip (of historical interest): • [http://en.wikipedia.org/wiki/Clipper_chip] • [http://www.epic.org/crypto/clipper/]

46. For wiretapping (provided by a court order), each clipper chip has • encryption algorithm in a chip • inserted into a phone. • Press button & security devices exchange encryption keys. • Designed by engineers at NSA w/ no input from private industry in response to private sectors developing their own to combat business and industrial espionage.

47. K = 80-bit session key to encrypt – needed for wiretap • F = 80-bit family key (all chips in a group have the same one) • N = 30-bit serial # (unique to a chip) • S = 80-bit secret key – unique to each chip, used by law enforcement

48. V = voice message – Ek(V) is the transmitted voice message • Clipper chip also generates EF(ES(K)+N) (+ is concatenate here)

49. Suppose a wiretap is approved; • Apply DF to above to get ES(K)+N. Easy since F is not secret • S IS secret so cannot apply DS easily. Need to use N to get S but first need to know how S is formed and stored.

50. Two parties – each generates one 80-bit string. Call them S1 and S2. • Calculate S= S1 S2 • Each of S1 and S2 are maintained by separate key escrow agencies along with chip serial number. Who the agencies are and who they report to is an issue.