Introduction To Basic Encryption
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
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.
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
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.
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.
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 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
2) The sender needs to exchange the key to the receiver. It may
be hijacked in between.
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
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 is an operation performed by a
function, which moves an element at place j to the
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
First, a description of the computation.