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# Group 6

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### Group 6

1. 1. Topic – E-COMMERCE
2. 2. Introduction To Basic Encryption and Decryption  The term ‘Cryptography’ means the concept of encryption and decryption together. Cryptography is the technique in which the original ‘plain text’ message is ‘encrypted’ i.e. converted into a coded form called ‘cipher text’ at the sender’s end, which is then transmitted to the receiver.
3. 3.  The receiver then ‘decrypts’ i.e. converts the ‘cipher text’ back into the ‘plain text’ to get the original message back.  Cryptography is also called as an art or technique to achieve the secure communication between the communicating parties by encoding the messages between them such that no 3rd party can gain anything useful out of interception.
4. 4.  Elliptic curve cryptography (ECC) is an approach to public-key cryptography based on the algebraic structure of elliptic curves over finite fields. Elliptic curves are also used in several integer factorization algorithms that have applications in cryptography, such as Lenstra elliptic curve factorization.  Cryptography is one of the essential technologies used in building a secure VPN. Different applications of the same basic algorithms can provide both encryption that keeps data secret and authentication that ensures the two security peers in a VPN are who they claim to be. This chapter introduces some basic concepts in cryptography and demonstrates how they can be used in practice to provide data confidentiality. The next chapter continues this theme with a discussion of mutual authentication using cryptographic algorithms.
5. 5.  Symmetric-key cryptography is also known as a secret- key, single key or private key.  An encryption system in which the sender and receiver of a message share a single, common key that is used to encrypt and decrypt the message.  Symmetric-key systems are simpler and faster, but their main drawback is that the two parties must somehow exchange the key in a secure way.  Public-key encryption avoids this problem because the public key can be distributed in a non-secure way, and the private key is never transmitted.
6. 6. Disadvantages of symmetric key: A symmetric-key algorithm has two major disadvantages. 1) Each pair of users must have a unique symmetric key. This means that if N people in the world want to use this method, there needs to be N(N -1)/2 symmetric keys. For eg: for 1 thousand people to communicate, 1000* 999 /2 =4,99,500 (4 lakhs 99 thousand and five hundred) symmetric keys are needed. The distribution of the keys between two parties can be difficult. 2) The sender needs to exchange the key to the receiver. It may be hijacked in between.
7. 7.  Category of Standard: Computer Security.  Explanation: The Data Encryption Standard (DES) specifies a FIPS approved cryptographic algorithm as required by FIPS 140-1.  Qualifications. The cryptographic algorithm specified in this standard transforms a 64-bit binary value into a unique 64-bit binary value based on a 56-bit variable. Data Encryption Standard
8. 8.  The algorithm is designed to encipher and decipher blocks of data consisting of 64 bits under control of a 64-bit key  A block to be enciphered is subjected to an initial permutation IP and then to a complex key- dependent computation and finally to a permutation which is the inverse of the initial permutation IP-1. Introduction
9. 9.  Permutation is an operation performed by a function, which moves an element at place j to the place k.  The key-dependent computation can be simply defined in terms of a function f, called the cipher function, and a function KS, called the key schedule.  First, a description of the computation.