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Public Key Cryptography 11,253 views Share Like Download ...
Public Key Cryptography • It is used two keys for encryption and for decryption. – a public-key, which may be known by a...
Gopal Sakarkar, Professor Follow Published on Sep 20, 2014
Public Key Cryptography,Rivest, Shamir & Adleman ,Diffe-Hellman Key ... Published in: Engineering 0 Comments 16 Likes Statistics Notes
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Public Key Cryptography 1. 1. Security Concept Part-2 Mr.Gopal Sakarkar Mr. Gopal Sakarkar 2. 2. Public Key Cryptography • It is used two keys for encryption and for decryption. – a public-key, which may be known by anybody, and can be used to encrypt messages – a private-key, known only to the recipient, used to decrypt Mr. Gopal Sakarkar messages • It has six ingredient 1 Plain text 2 Encryption algorithm 3 Public and private keys 4 Ciphertext 5 Decryption algorithm 3. 3. Mr. Gopal Sakarkar 4. 4. Public-Key Characteristics • Public-Key algorithms rely on two keys where: – it is computationally infeasible to find decryption key knowing only algorithm & encryption key – it is computationally easy to en/decrypt messages when the relevant (en/decrypt) key is known – either of the two related keys can be used for encryption, with the other used for decryption (for some algorithms) Mr. Gopal Sakarkar 5. 5. Public key Cryptosystem : Authentication and secrecy Mr. Gopal Sakarkar 6. 6. Requirement of Public key Cryptography 1. It is easy for party B to generate a pair of keys (public key PUb , Mr. Gopal Sakarkar Private key PRb). 2. It is easy for a sender A , knowing the public key and message to be encrypt. C=E(PUb, M) 3. It is easy for receiver B to decrypt the resulting ciphertext using the private key . Requirement of Public key Cryptography 1. It is easy for party B to generate a pair of keys (public key PUb , Mr. Gopal ... M=D(PRb,C)=D[PRb,E(PUb,M)] 4. It is infeasible for an any person , to know the public key PUb to determine the private key PRb. 5. It is infeasible for any person to know the public key PUb and a ciphertext C to recover the original message M. 6. Two keys can be applied in either order M=DP[PUb, E(PRb,M)] = D[PRb,E(PUb, M)] 7. 7. Exercise • Explain the difference between conventional and public key encryption. • What are the different requirements for public key cryptography . Mr. Gopal Sakarkar 8. 8. Related Links • http://docs.sun.com/source/816-6154-10/contents.htm Mr. Gopal Sakarkar 9. 9. RSA • Invented by Rivest, Shamir & Adleman of MIT in Mr. Gopal Sakarkar 1977 • It is a best known & widely used public-key scheme. • It is a block cipher algorithm in which palintext and ciphertext integers between 0 to n-1 for some n. • A typical size for n is 1024 bits or 309 decimal digits. 10. 10. RSA Algorithm Mr. Gopal Sakarkar 11. 11. Mr. Gopal Sakarkar 12. 12. Mr. Gopal Sakarkar 13. 13. An Example • Let p= 3 and q=5, • n= 3 X 5 =15 • Q(n)= (3-1) * (5-1) = 2 x 4= 8 • Select e such that gcd(Q(n), e) =1 where, 1