1. Unit – 1 Security Requirements OSI Security Architecture Security Attacks, Mechanisms and Services Cryptography Conventional Encryption Symmetric Key Cryptography – Substitution Techniques – Transposition Techniques – Rotor Machines – Steganography – Possible types of attacks.

2. Security Services Message confidentiality Message Integrity Message non-reproduction Message Authentication

3. Security Requirements – CIA Triad

4. Confidentiality Data Confidentiality:- Private Information not disclosed to unauthorized. Privacy Data integrity System integrity Availability

5. The OSI – Security Architecture To assess effectively the security needs of an organization and to evaluate and choose various security products and policies, some systematic way of defining the requirements for security is required. ITU-T Recommendation X.800, Security Architecture for OSI, defines such a systematic approach The OSI security architecture focuses on security attacks, mechanisms, and services.

6. The OSI – Security Architecture Security attack Security mechanism Security service

7. Security Attacks Passive Attacks - eavesdropping on, or monitoring of, transmissions to: – obtain message contents, or – monitor traffic flows Active Attacks – modification of data stream to: – masquerade of one entity as some other – replay previous messages – modify messages in transit – denial of service

8. Security Attacks (Passive)

9. Security Attacks (Active)

11. Security Mechanisms

12. Security Services

13. Model for Network Security

14. Model for Network Access Security

15. Cryptography – Basic Terminologies Plain Text-Original Text Encryption algorithm-Transformed Text on the plain text. Secret key Cipher text Decryption algorithm

16. Cryptography Symmetric Substitution & Transposition Block CipherDESAES Stream Cipher AsymmetricRSA Diffie- Hellman El-GamalElliptic Curve

17. Model of Symmetric Cryptosystem

18. Simplified Model of Symmetric Encryption

19. Cryptographic System Cryptographic systems are characterized along three independent dimensions: 1. The type of operations used for transforming plaintext to ciphertext. All encryption algorithms are based on two general principles: substitution, in which each element in the plaintext (bit, letter, group of bits or letters) is mapped into another element, and transposition, in which elements in the plaintext are rearranged. The fundamental requirement is that no information be lost (that is, that all operations are reversible). Most systems, referred to as product systems, involve multiple stages of substitutions and transpositions.

20. Cryptanalytic Attacks

21. Symmetric Key Cryptography Substitution Techniques Transposition Techniques Block Cipher – DES – AES Stream Cipher

22. Symmetric Key Cryptography Substitution Techniques – Mono-alphabetic Ciphers Shift Cipher Caesar Cipher Play-fair Cipher – Polyalphabetic Ciphers Vigenere Cipher Hill Cipher

23. ABCDEFGHIJKLMNOPQRSTUVWXYZ 123456789 1011121314151617181920212223242526 Plain Text=HELLO Key=4 E=(pi+k) mod 26 D=(ci-k) mod 26 E(H)=(8+4) mod 26=12 mod 26=12(L) E(E)=(5+4) mod 26=9 mode 26=9(I) E(L)=12+4 mod 26=16 mod 26=16(P) E(O)=15+4 mod 26= 19 mod 26=19(S) PT=HELLO CT=LIPPS D(L)=12-4 mod 26=8 mod 26= 8(H)

24. Play-fair Cipher The key square is a 5×5 grid of alphabets that acts as the key for encrypting the plaintext. Each of the 25 alphabets must be unique and one letter of the alphabet (usually J) is omitted from the table (as the table can hold only 25 alphabets). If the plaintext contains J, then it is replaced by I. The plaintext is split into pairs of two letters (digraphs). If there is an odd number of letters, a Z is added to the last letter. If both the letters are in the same column: Take the letter below each one (going back to the top if at the bottom). If both the letters are in the same row: Take the letter to the right of each one (going back to the leftmost if at the rightmost position). If neither of the above rules is true: Form a rectangle with the two letters and take the letters on the horizontal opposite corner of the rectangle.

25. Play fair THE HOUSE ISBEING SOLD TONIGHT  PT GUIDANCE --  Key TH EH OU SE IS BE IN GS OL DT ON IG HT E(TH)=PO E(EH)=NL E(OU)=KA E(SE)=RB E(IS)=DR E(BE)=FB E(IN)=GE E(GS)=DP E(OL)=HM E(Dt)=as E(ON)=HF E(IG)=DU E(HT)=OP PONLKARBDRFBGEDPHMASHFDUOP GUI/JDA NCEBF HKLMO PQRST VWXYZ

26. Plain Text =instruments Key=network In st ru me nt sz E(in)=do E(st)=po E(ru)=dn E(me)=kv E(nt)=ew E(SZ)=zo Plain Text=insruments Cipher=dopodnkvewzo netwo rkabc dfghi/j lmpqs uvxyz

27. Vigenere Cipher Vigenère square or Vigenère table – The table consists of the alphabets written out 26 times in different rows, each alphabet shifted cyclically to the left compared to the previous alphabet, corresponding to the 26 possible Caesar Ciphers. Caesar Ciphers – At different points in the encryption process, the cipher uses a different alphabet from one of the rows. – The alphabet used at each point depends on a repeating keyword.

28. Vigenère square or Vigenère table

29. Cryptography ---pt --row Luckyluckylu—key ---column Cipher Text=nlaz

30. Plain Text=helloworld---row Key=Ayushayush----column Cipher text=hcfdvwmldk Decryption Cipher text=hcfdvwmldk– vlaue Key=Ayushayush---row Plain text=hellworld

31. Hill cipher Key=GYBNQKURP(3*3) PT=hel low orl dab(3*1) Pt=HEL=WQH D( c ) Inverse k= 1/|K|*adj K ABCDEFGHIJKLMNOPQRSTUVWXYZ 123456789 1011121314151617181920212223242526 7252 141711 211816 8 5 12 205 329 450 23 17 8 8510 218 128 7252 141711 211816 23 17 8

32. Key =4*4 Pt=4*1 E=k*p mod 26 D=k inverse *c mod 26

33. Symmetric Key Cryptography Transposition Techniques – Rail Fence Cipher – Permutation Cipher – Columnar Transposition Ciphers

34. Rail Fence Cipher Plain text= welcome to my session W l o e o y e s o e c m t m s s i n Cipher text=wloeoyesoecmtmssin

35. Columnar Transposition Ciphers Plain text= welcome to my session Key=4 2 3 1 Cipher text=ctsiyemmsnleysxwooeo 4231 welc omet omys essi onxy