Sunday Academy Computer Security Activities 2013-2014

1. Planned Activities on Computer Security for Sunday Academy2013-2014 Jun Liu, Jason Waskiewicz, Allen Nash

2. Time Schedule • 11:00-11:15 Cultural Connection • 11:15-11:45General Introduction • 11:45-12:00 Activity 1: Hands-on Practice on Symmetric-Key Ciphers. • 12:00-12:30 Lunch • 12:30-1:00 continue on with Activity 1. • 1:00-2:00 Activity 2: Hands-on Practice on Asymmetric-Key Ciphers. • 2:00-2:45 Activity 3: Zero-Knowledge Proof. • 2:45-3:00 Wrap-up and Evaluation

3. What We Are Going To Learn? • Understanding the general goals of security. • Understanding the essential concerns in achieving the general goals of security. • Learning a few cryptographic methods. • Learning to evaluate the weakness of a cryptographic method.

4. Goals of Security • Confidentialityis the most common aspect of information security, which is to protect the confidential information. • Integrity means that changes on information can only be done by authorized entities. • Availability means that information needs to be accessible to authorized entities.

5. Common Attacks • Attacks Threatening Confidentiality • Snooping refers to unauthorized access to or interception of data. • Attacks Threatening Integrity • Modificationmeans that the attacker intercepts the message and changes it. • Masqueradingmeans the attacker impersonates somebody else. • Attacks Threatening Availability • Denial of service (DoS)may slow down or totally crash the service of a system.

6. Security Services • Data confidentiality is to fight against the attacks threatening confidentiality. • Security mechanism: encipherment • Data integrity is to fight against the attacks threatening integrity. • Security mechanism: encrypted digest • Access control is to fight against the attacks threatening availability.

7. Security and Cultural Relations • Navajo Code Talkers • http://www.navajocodetalkers.org/ • They were a small band of warriors who created an unbreakable code from the ancient language of their people and changed the course of modern history. • When America's best cryptographers were falling short, they were able to use their language as a successful code. • They have served with distinction in every major engagement of the Pacific war field from 1942-1945, their unbreakable code played a pivotal role in saving countless lives and hastening the war's end.

8. Common Attacks (1) • Phishing Attacks • The act of sending an e-mail to a user falsely claiming to be an established legitimate enterprise. • Such attacks are the attempts to steal the identity by fooling the user to provide the private identity information. • The e-mail directs the user to visit a bogus Web site and to update personal information: • such as passwords, credit card information, social security numbers, and bank account information. • Actually, the personal information will be recorded by the attackers who will use the personal information to illegally access a user’s actual account at the established legitimate enterprise. • Suggestion to fighting against phishing attacks: • Making sure that you are accessing the legitimate enterprise website before you provide any personal information.

9. Common Attacks (2) • Phishing Attacks • Example

10. Common Attacks (3) • Phishing Attacks • Signs of phishing emails • Generic greeting • Phishing emails are usually sent in large batches. • To save time, Internet criminals use generic names like "First Generic Bank Customer” to avoid typing all recipients' names out. • Suggestion: If you don't see your name, be suspicious. • Forged link • Even if a link has a name you recognize somewhere in it, it doesn't mean it links to the real organization. • Suggestion: • Roll your mouse over the link and see if it matches what appears in the email. If there is a discrepancy, don't click on the link. • Websites where it is safe to enter personal information begin with "https" — the "s" stands for secure. If you don't see "https" do not proceed.

11. Common Attacks (4) • Phishing Attacks • Signs of phishing emails • Requests personal information • The point of sending phishing email is to trick you into providing your personal information. • If you receive an email requesting your personal information, it is probably a phishing attempt. • Sense of urgency • Internet criminals want you to provide your personal information now. They do this by making you think something has happened that requires you to act fast.

12. Common Attacks (5) • Phishing Attacks • Forged website

13. Common Attacks (6) • Keylogging • Keyloggeris a software program or hardware device that is used to monitor and log each of the keys typed through a computer keyboard. • The user who installed the program or hardware device can view all keys. • Keyloggers allow your information to be transmitted to an unknown third party. • Some keyloggers capture screens, rather than keystrokes. • Some keyloggerscan also secretly turn on video or audio recorders, and transmit the recorded information over your internet connection.

14. Common Attacks (7) • Software Keylogger • It is a program that can record each stroke on the keyboard. • It will automatically start capturing keystrokes as soon as the computer is turned on and remain undetected in the background. • It can be programmed to send a summary of all the keystrokes via email.

15. Common Attacks (8) • Hardware Keylogger • Itusually looks like a USB drive which can be connected to the victim's computer. • It comes with the keylogging software which is pre-installed on the device. • A summary of the keystrokes is recorded on the USB drive.

16. Common Attacks (9) • How to protect yourself from key logging • Use a firewall. • Keyloggersusually send information through the internet. • Afirewall will monitor your computer's online activity and sniff out the suspicious data transmission. • Install a password manager. • Keyloggerscan't steal what you don't type. • Password mangers automatically fill out important forms without making you to type anything in. • Update your software. • Once a company knows of any exploits in their software, it works on an update to deal with the exploitation. • Change passwords. • If you still don't feel protected, you can change your password frequently.

17. Planned Activities • Three activities have been planned: • Activity 1: Hands-on practice on traditional symmetric-key ciphers. • Activity 2: Hands-on practice on asymmetric-keycryptography. • Activity 3: Hands-on practice on zero-knowledge proof.

18. Activity 1: Symmetric-Key Ciphers

19. Activity 1Examples of Symmetric-Key Ciphers • We will look into a few examples of Symmetric-Key Ciphers to see how they work. • Caesar cipher: Julius Caesar used an additive cipher to communicate with his officers. • Caesar used a key of 3 for his communications. • Vigenerecipher: It is an example of polyalphabetic substitution cipher. • Transposition cipher: It does not substitute one symbol for another, instead it changes the location of the symbols.

20. Activity 1Caesar cipher (1) • It is the earliest known substitution cipher made by Julius Caesar. • It is the first attested use in military affairs. • It replaces each letter by the 3rd letter on the right. • The transformation is defined as a b c d e f g h i j k l m n o p q r s t u v w x y z D E F G H I J K L M N O P Q R S T U V W X Y Z A B C • Example: Plaintext: meet me after the toga party Ciphertext: PHHW PH DIWHU WKH WRJD SDUWB

21. Activity 1Caesar cipher (2) • The security of the mono-alphabetic substitution cipher • We could follow a brute force search approach by simply trying each possible key in turn. • When given a cipher text, just try all shifts of letters until we see meaningful text. • Another systematic way of cracking the Caesar cipher is to use the features in English language. • Human languages are redundant, and characters are not equally commonly used. • In English, E is by far the most common letter, followed by T,R,N,I,O,A,S. • Other letters like Z,J,K,Q,X are fairly rare.

22. Activity 1Caesar cipher (3)

23. Activity 1Caesar cipher (4) • Mono-alphabetic substitution ciphers do not change the relative letter frequencies. • Attackers can simply calculate the letter frequencies for cipher text and compare the counts against known values. • To solve the ties, tables of common double/triple letters help a lot. • Example: • given cipher text: UZQSOVUOHXMOPVGPOZPEVSGZWSZOPFPESXUDBMETSXAIZ VUEPHZHMDZSHZOWSFPAPPDTSVPQUZWYMXUZUHSX EPYEPOPDZSZUFPOMBZWPFUPZHMDJUDTMOHMQ • count relative letter frequencies. • P Z U S O M H D E X V W F T Q Y G A B Y I J • 16 14 10 10 9 8 7 6 6 5 5 4 4 3 3 2 2 2 2 2 1 1 • guess Pand Z are e and t, respectively. • guess ZW is th and hence ZWP is the. • proceeding with trial and error finally get: it was disclosed yesterday that several informal but direct contacts have been made with political representatives of the vietcong in moscow

24. Activity 1Caesar cipher (5) • Relative letter frequencies P: e t i a s o c n _ _ _ h _ m w _ _ _ _ _ _ C: P Z U S O M H D E X V W F T Q Y G A B I J 16 14 10 10 9 8 7 6 6 5 5 4 4 3 3 2 2 2 2 1 1 • Partial translation: itwasiscoseeste a thatse e a in o m UZQSOVUOHXMOPVGPOZPEVSGZWSZOPFPESXUDBMET a t iectcontactsha e eenmaewith o it SXAIZVUEPHZHMDZSHZOWSFPAPPDTSVPQUZWYMXUZ ica e esentatieso the ietconinmoscow UHSXEPYEPOPDZSZUFPOMBZWPFUPZHMDJUDTMOHMQ

25. Activity 1Caesar cipher (6) • We continue to work on the translation P: e t i a s o c n _ _ _ h _ m w _ _ _ _ _ _ C: P Z U S O M H D E X V W F T Q Y G A B I J 16 14 10 10 9 8 7 6 6 5 5 4 4 3 3 2 2 2 2 1 1 E  r itwasiscoseestera thatseera in orm UZQSOVUOHXMOPVGPOZPEVSGZWSZOPFPESXUDBMET a t irectcontactshae eenmaewith o it SXAIZVUEPHZHMDZSHZOWSFPAPPDTSVPQUZWYMXUZ icare resentatieso the ietconinmoscow UHSXEPYEPOPDZSZUFPOMBZWPFUPZHMDJUDTMOHMQ

26. Activity 1Caesar cipher (7) • We continue to work on the translation P: e t i a s o c n rl_ h _ m w _ _ _ _ _ _ C: P Z U S O M H D E X V W F T Q Y G A B I J 16 14 10 10 9 8 7 6 6 5 5 4 4 3 3 2 2 2 2 1 1 X l itwasisclose estera thatseeralinorm UZQSOVUOHXMOPVGPOZPEVSGZWSZOPFPESXUDBMET alt irectcontactshae eenmaewitholit SXAIZVUEPHZHMDZSHZOWSFPAPPDTSVPQUZWYMXUZ icalreresentatieso the ietconinmoscow UHSXEPYEPOPDZSZUFPOMBZWPFUPZHMDJUDTMOHMQ

27. Activity 1Caesar cipher (8) • We continue to work on the translation P: e t i a s o c n rldh _ m w _ _ _ _ _ _ C: P Z U S O M H D E X V W F T Q Y G A B I J 16 14 10 10 9 8 7 6 6 5 5 4 4 3 3 2 2 2 2 1 1 V  d itwasdisclosedesterdathatseeralinorm UZQSOVUOHXMOPVGPOZPEVSGZWSZOPFPESXUDBMET altdirectcontactshae eenmadewitholit SXAIZVUEPHZHMDZSHZOWSFPAPPDTSVPQUZWYMXUZ icalreresentatieso the ietconinmoscow UHSXEPYEPOPDZSZUFPOMBZWPFUPZHMDJUDTMOHMQ

28. Activity 1Caesar cipher (9) • We continue to work on the translation P: e t i a s o c n rldh vm w _ _ _ _ _ _ C: P Z U S O M H D E X V W F T Q Y G A B I J 16 14 10 10 9 8 7 6 6 5 5 4 4 3 3 2 2 2 2 1 1 F v itwasdisclosedesterdathatseveralinorm UZQSOVUOHXMOPVGPOZPEVSGZWSZOPFPESXUDBMET altdirectcontactshaveeenmadewitholit SXAIZVUEPHZHMDZSHZOWSFPAPPDTSVPQUZWYMXUZ icalreresentativesothevietconinmoscow UHSXEPYEPOPDZSZUFPOMBZWPFUPZHMDJUDTMOHMQ

29. Activity 1Caesar cipher (10) • We continue to work on the translation P: e t i a s o c n rld h v m w p yb_ _ _ C: P Z U S O M H D E X V W F T Q Y G A B I J 16 14 10 10 9 8 7 6 6 5 5 4 4 3 3 2 2 2 2 1 1 itwasdisclosedyesterdaythatseveralinorm UZQSOVUOHXMOPVGPOZPEVSGZWSZOPFPESXUDBMET albtdirectcontactshavebeenmadewithpolit SXAIZVUEPHZHMDZSHZOWSFPAPPDTSVPQUZWYMXUZ icalrepresentativesothevietconinmoscow UHSXEPYEPOPDZSZUFPOMBZWPFUPZHMDJUDTMOHMQ • Proceeding with trial and error finally get: it was disclosed yesterday that several informal but direct contacts have been made with political representatives of the vietcong in moscow

30. Activity 1Vigenerecipher (1) • It is the simplest example of the polyalphabetic substitution ciphers. • It improve security of Caesar ciphers by using multiple letters. • It makes cryptanalysis harder with the flatter frequency distribution. • A key is multiple letters long K = k1 k2 ... kd • The ithletter specifies ith alphabet to use. • Use each alphabet in turn. • Repeat from start after d letters in message. • Decryption simply works in reverse.

31. Activity 1Vigenerecipher (2) • An Example of VigenèreCipher • The keyword is: deceptive • key: session 1|session 2| session 3 deceptivedeceptivedeceptive 3 4 2 4 15 19 8 21 4 3 4 2 4 15 19 8 21 4 3 4 2 4 15 19 8 21 4 • Plaintext: wearediscoveredsaveyourself • ciphertext: ZICVTWQNGRZGVTWAVZHCQYGLMGJ • Relative frequency (flatter) G V Z C T W Q A M I J L N R Y 4 3 3 2 2 2 2 1 1 1 1 1 1 1 1

32. Activity 1Vigenerecipher (3) • Security of VigenèreCipher • The letter frequencies are obscured because that one plaintext letter may corresponds tomultiple ciphertext. • But, the letter frequencies are not totally lost. • Steps of cracking • Start with letter frequencies to see if look monoalphabeticcipher or not. • If not, then need to determine number of alphabets, since then can attach each. • The KasiskiMethod can be used to crack the VigenèreCipher.

33. Activity 1Transposition cipher (1) • The transposition cipher is to divide the plaintext into groups of predetermined size, called blocks, and then use a key to permute the characters in each block separately. • It will make the cipher text to have the same frequency distribution as the original text. • The encryption key is the size of the blocks.

34. Activity 1Transposition cipher (2) • Plaintext: ‘WE ARE DISCOVERED. FLEE AT ONCE’ • First, removingpunctuationsanwrite the text in a row: WEAREDISCOVEREDFLEEATONCE • Organizing the plaintextinto a block for a blocksize of 6: W E A R E D IS C O V E R E DF L E E A T O N C E Q K J E U • Then, reading the textcolumnwise and put the textinto a rowto form the cipher: WIREE ESEAQ ACDTK ROFOJ EVLNE DEECU • In order to restore the plaintext from the cipher, we musthave to know the blocksize. • The blocksizeis the secretwhichisonlyknown to Alice and Bob.

35. Activity 1Transposition cipher (3) • Exercise: • Ciphertext: WIESHNMSEGEONWMUDABRRTECIERENRIZKRTZ • Whatis the plaintext? • Hint: Youhave to guess the size of the block. • Time limit: 1 minute.

36. Activity 1Transposition cipher (4) • Exercise: • Ciphertext: WIESHNMSEGEONWMUDABRRTECIERENRIZKRTZ • Whatis the plaintext? • Hint: Youhave to guess the size of the block. • Answer: • Key: 4 • Plaintext: Whendrinkingwater, rememberitssource.

37. Activity 2: Asymmetric-Key Cryptography (1) • Symmetric-key cryptography is based on sharing secrecybetween Alice and Bob. • The shared key has to be updated periodically. • It is difficult to send the new key to Alice and Bob. • There is a need that the secrecy is not sent. • The solution is the asymmetric-key cryptography which is based on personal secrecy.

38. Activity 2: Asymmetric-Key Cryptography (2) • Asymmetric-key cryptography uses two separate keys: one private key and one public key. • The private key is never sent out from the key owner. • The public key is supposed to be known by everyone in the world. • Plaintext and cipher text are treated as integers in asymmetric-key cryptography. • The main idea behind asymmetric-key cryptography is the concept of the trapdoor one-way function.

39. Activity 2: Asymmetric-Key Cryptography (3)

40. Activity 2: Asymmetric-Key Cryptography (4) One-Way Function (OWF) 1. f is easy to compute. 2. f −1 is difficult to compute. Trapdoor One-Way Function (TOWF) 3. Given y and a trapdoor, x can be computed easily.

41. Activity 2: Asymmetric-Key Cryptography (5) • Example of trapdoor one-way function • For two large prime numbers pand q. • n= p × q is a one-way function. • Given p and q , it is always easy to calculate n; • Given n, it is very difficult to compute p and q when pand q are large. • When given n and one of the factors, it becomes easy to calculate the other factor.

42. Activity 2: Asymmetric-Key Cryptography (6) • A difficult calculation: • Given a sequence [295, 592, 301, 14, 28, 353, 120, 236] and a value 1129 • It is known that the value 1129 is a sum of a portion of the sequence. • Can you quickly figure out the items in the sequence, which are used to form the value of 1129?

43. Activity 2: Asymmetric-Key Cryptography (7) • An easy calculation: • Given a new sequence [2, 7, 11, 21, 42, 89, 180, 354] and a value 372 • It is known that the value 372 is a sum of a portion of the sequence. • Can you quickly figure out the items in the sequence that are used to form the value of 372?

44. Activity 2: Asymmetric-Key Cryptography (8) • The sequence [2, 7, 11, 21, 42, 89, 180, 354] is super-increasing. • The decomposition of 372 is very easy.

45. Activity 2: Asymmetric-Key Cryptography (9) • Example asymmetric-key cipher • Public key: [295, 592, 301, 14, 28, 353, 120, 236] • Cipher: 1129 • Private key: [2, 7, 11, 21, 42, 89, 180, 354] • Plaintext: a

46. Activity 2: Asymmetric-Key Cryptography (10) • We play a simple game to show the procedure of the knapsack cryptosystem. • First, I create a pair of private and public keys. • Second, I publish my public key to everyone. • The public key consists of 8 integers. • Public key = [295, 592, 301, 14, 28, 353, 120, 236]. • Third, I keep the private key as a personal secret. • Fourth, each of you choose a character and encodes the character into an 8-bits representation. • For example, the character ais expressed as 01100001. • Fifth, you encode the plaintext into a cipher. • For example, the cipher text of plaintext a is integer 1129. • 0*295+1*592+1*301+0*14+0*28+0*353+0*120+1*236 = 1129 • Sixth, you show your cipher to others to let them to guess what your original character is (without disclosing your original character).

47. Activity 2: Asymmetric-Key Cryptography (11) • The key owner can always quickly get to know the original character, once you show me the cipher. • The trick lies in the way that the key is generated. • The length of the public key consists of 8 integers • Choosing a supper-increasing sequence • [2, 7, 11, 21, 42, 89, 180, 354]. • The sum of the sequence of the private key is n=881. • Another integer r=588 is chosen to cook the private key into a public key through • (2 * 588) mod 881 = 295 • (7 * 588) mod 881 = 592 • (11 * 588) mod 881 = 301 • (21 * 588) mod 881 = 14 • (42 * 588) mod 881 = 28 • (89 * 588) mod 881 = 353 • (180 * 588) mod 881 = 120 • (354 * 588) mod 881 = 236 • The inverse of r is r-1 = 442. • It can be verified that r *r-1= 588*442 mod 881 = 1 mod 881 • Public key = [295, 592, 301, 14, 28, 353, 120, 236] • Private key = {[2, 7, 11, 21, 42, 89, 180, 354], n=881, r=588}.

48. Activity 2: Asymmetric-Key Cryptography (12) • I show that how I can quickly find out the original character. • Suppose I get the cipher C=1129. • I compute • C * r-1 mod n • = 1129 * 442 mod 881 = 372. • Next, I decompose372 based on the super-increasingsequence. (see the table on the right) • The plaintext is a • a = 01100001 • Note: the decompositionalways starts from the largernumbers and continues to smaller numbers.

49. Activity 3: Zero-Knowledge Proof (1) • An essential question: • How to convince someone that you have the solution to a problem, without revealing any detail of your solution to others? • Example: • You have a secret or a new invention. • You want to sell your secret/invention to the potential buyers. • A dilemma: • The buyers won’t pay you before they are convinced by the truthfulness of your secret/invention. • You won’t disclose more details of your secret/inventionbefore you get paid.

50. Activity 3: Zero-Knowledge Proof (2) • The solution: zero-knowledge proof. • The proof consists of a prover and a verifier. • In our example, • the owner of a secret/invention is the prover; • a potential buyer is the verifier. • The prover interacts with the verifier to prove the truthfulness of the secret/invention. • The prover should prove the truthfulness of the secret/invention, without revealing any detail. • Whatever can be learned from the proof, can be learned without it.