A Seminar on the topic CRYPTOGRAPHY Presented by: Himanshu Vyas IV yr,VIII semester Batch-A2

1. A Seminar on the topic CRYPTOGRAPHY Presented by: Himanshu Vyas IV yr,VIII semester Batch-A2

2. Introduction to cryptography • It is the science of writing in secret code & it is an ancient art • It is called an ancient art because it was used during war times for forming battle plans. • It is necessary while communicating over untrusted medium like internet.

3. Why cryptography required Security requirements are: • Authentication:- to prove one’s identity • Privacy/confidentiality:-to ensure that no one can read except the intended receiver. • Integrity:-The message received by receiver is not altered. • Non repudiation:-to prove that sender has really sent the message.

4. How cryptography works • The message to be sent is known as plaintext that is the original message. • Plaintext is then converted into some unreadable form by some algorithms and by a key. • These algos are known as ciphers. • The unreadable form is known as ciphertext.

5. Encryption & Decryption • The process of conversion of plaintext( the original message) to ciphertext (encoded message) is known as encryption. • The process of conversion of ciphertext to plaintext is known as decryption. • Encryption is used by militaries & governments for secret communications. • Encryption is used in many kinds of civilian systems like internet e-commerce,mobile telephone.

6. Ciphertext contains all the information of Plaintext message but not in a format readable by human or computer without a proper mechanism to decrypt it.

8. Cipher & its types • Cipher is an algorithm for performing encryption and decryption -that is a series of well defined steps. • Types of ciphers:- • Historical ciphers • Modern ciphers

9. Historical ciphers:- • Also known as classical ciphers. • These are of 2 types:- Substitution ciphers:-in this one alphabet is substituted for other eg.:-GOOD DOG can be encrypted as- PLLX XLP Here P is substituted for G L is substituted for O X is substitutes for D

10. Transposition cipher:-In this letters are transposed. Eg:-GOOD DOG can be encrypted as DGOGDOO The early version of cipher is Ceaser’s cipher named after Julius Ceaser who used it first

11. Ceaser’s Cipher • It substitutes one piece of information to other. • Algorithm is to offset the alphabet and the key is the number of characters to offset it. Example A B C D E F G H I J K L M N O P QR S T U V W X Y Z Sliding every character by three 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 Using this scheme SECRET=>VHFUHW

12. 2)Modern ciphers Classification on the type of key used • Symmetric key algo • Asymmetric key algo Classification on the basis of type of input • Block cipher-encrypt block of data • Stream cipher-encrypt continuous streams of data

13. Key • Key is apiece of information(or a parameter,set of rules)that determines the functional output of a cryptographic algo • Without the key algo would have no meaning.

14. Types of cryptographic algos • Secret key cryptography:- Also known as symmetric /private key algo.It uses single key for encryption & decryption. • Public key cryptography:-Also known as asymmetric key algo,it uses one key for encryption and another key for decryption • Hash functions:-uses some mathematical functions to encrypt information.

16. Symmetric key cryptography • Also known as secret key,private key cryptography. • Single key is used for encryption as well as for decryption. • The key must be known to both the sender & the receiver.

18. Some secret key cryptographic algorithms are: • Data encryption standard(DES) • It was designed by IBM in 1970 • It is a block cipher employing 56 bit key on a 64 bit block • It is designed to yield fast hardware implementations and slow software implementations

19. Advanced Encryption Standard(AES) • It was designed in 1997 for US government • The algo can use variable block length and key length. • The key lengths&block lengths can be of 128,192 or 256 bits

20. INTERNATIONAL DATA ENCRYPTION ALGO(IDEA) • It was developed in 1992 • It is 64 bit block cipher and key size is129 bit Other algos are:- Cast128/256,Rivestciphers,Blowfish,Twofish,camilla,MISTY1,kasaumi,seed,skipjack.

21. Public key cryptography • Also known as asymmetric key cryptography. • Uses two keys public&private. • Private key is kept secret & public key may be widely distributed. • The message encrypted with a public key can be decrypted only with its corresponding private key. • Two main branches of it are: Public key encryption Digital signatures

22. A big random number is used to make a public-key/private-key pair.

23. Anyone can encrypt using the public key, but only the holder of the private key can decrypt. Secrecy depends on the secrecy of the private key.

24. Algos used are: • RSA • Developed by Ronald Rivest,Adi Shamir and Leonard Adleman • It is used for key exchange,digital sign,or encrypting small blocks of data. • The key-pair is the product of two prime nos,the primes can be 100 or more digits in length each. • It is safe as it is difficult to factor large prime nos.

25. Some other algos are: Diiffie-Hellman,Digital siganture algo,Elgamal,Elliptic curve cryptography.

26. Digital Signatures • It is a type of asymmetric cryptography • There are two algos one for signing which uses user’s private key and one for verifying which uses user’s public key. • The output of signature process is called digital signature.

27. Using a private key to encrypt (thus signing) a message; anyone can check the signature using the public key. Validity depends on private key security.

28. Benefits of digital signatures • Authentication:-Secret key is bound to a specific user and a sign shows that message was sent by that user. • Integrity:-If message is digitally signed then any change will invalidate the signature.

29. Drawbacks of digital signature • No certainty about the date & time at which the document was signed.

30. Hash Functions • Also known as one way encryption technique and use no key. • In this a fixed length hash value is computed • Hash algos are used to provide a digital fingerprint of a file’s content which ensures that a file has not been altered by an intruder or by a virus. • Hash functions are employed by many os to encrypt passwords.

31. Hash algorithms • Message Digest:-Produce a128 bit hash value from any arbitrary message. • Secure Hash Algo:-Produce 160 bit hash value. • HAVAL(Hash of variable length):-can create hash values that are 128,160,192,224 or 256 bits in length. • Whirlpool:-operates on messages less than 2^256 bits in length. • Tiger:-produces a192 bit output and compatible with 64 bit architechtures.

32. Benefits&drawback of cryptography • Benefits • Protects secret information from unauthorized access. • Protect against message forgeries. • It is an essential information security tool.

33. Drawbacks • Intruders can access stored files • Intruders can design such software which can easily access the key or plaintext • Transactions are beyond reach of government • It can be safe heavens for criminal activity • If the key is lost led important information inaccessible • Threatens national security by interfering with foreign illegal operations

34. Conclusion • Cryptography is an international threat stimulated by internet • Encryption challenges ability if law enforcement agencies to fight terrorism and crime • Led to social disorder • It can facilitate products that supports information security requirements of global information infrastructures • Key escrow encryption can meet allowing government to fight against crime confidentiality needs of organizations

35. THANK YOU