1. RSA Implementation

2. What is Encryption ? Encryption is the transformation of data into a form that is as close to impossible as possible to read without the appropriate knowledge

3. Why is cryptography important? Cryptography on the Internet –online banking, online trading, and make online purchases Authentication –Authentication is any process through which one proves and verifies certain information Access Control –Such as in file systems

4. What are the more popular techniques in cryptography ? secret-key public-key

5. Secret Key Also referred to as symmetric cryptography The same key is used for both encryption and decryption The most popular secret-key cryptosystem in use today is the Data Encryption Standard

6. Public-Key Each user has a public key and a private key The public key is made public while the private key remains secret Encryption is performed with the public key while decryption is done with the private key The RSA public-key cryptosystem RSA stands for Rivest, Shamir, and Adleman

7. Techniques in Cryptography RSA(Rivest, Shamir, Adleman) DES(Data Encryption Standard) AES(Advanced Encryption Standard)

8. RSA algorithm Take two large primes, p and q Compute their product n = pq Choose e, less than n and relatively prime to (p-1)(q-1) Choose d such that (ed - 1) is divisible by (p-1)(q-1)

9. RSA algorithm (cont’d) The values e and d are called the public and private exponents The public key is the pair (n, e) The private key is (n, d) The factors p and q may be destroyed or kept with the private key.

10. Encryption With RSA Suppose Alice wants to send a message m to Bob. Alice creates the ciphertext c such that c = m e mod n, where e and n are Bob's public key. She sends c to Bob. To decrypt, Bob makes m = c d mod n; the relationship between e and d ensures that Bob correctly recovers m. Since only Bob knows d, only Bob can decrypt this message.

11. Encryption validity duration What is the reason for which key expiration is needed ? Key size should always be chosen according to the expected lifetime of the data

12. RSA algorithm used for privacy Alice wishes to send an encrypted message to Bob She first encrypts the message with DES, using a randomly chosen DES key. Using bob’s public key she encrypts the DES key. Sending DES-encrypted message and the RSA-encrypted DES key Bob do this process inversely

13. Reference http://www.rsasecurity.com