a) Cryptography basics (00:21):
how do we provide this security during transmission? Well, One way of ensuring security can be use of CRYPTOGRAPHY!
Cryptography is a field of network security
which deals with hiding "real" infromation
when it is under transmission between the two parties.
Usually, the real information is transformed
or hidden into another message and transmitted over the network.
This transformed message in itself will make no sense
even if any hacker gets hold of this information.
When it reaches the destination,
the receipent will know a method to de-transform
the garbage message into the original information
which the sender had sent.method of transforming message at sender's side
and de transforming at reciever's side forms the basic model of Cryptography.
b) Encryption and Decryption
First, the information to be transmitted, called as plain text(or message)
is fed to an Encryption system.
The Encyrption system uses a key to convert the plain text to encyrpted form
which looks like garbage value.
This is also called as cipher text.
A corresponding key is used at the other end
to decrypt the cipher text back to original message.
When we say a key, it actually means a piece of string value
which is fed to encyprtion and decryption algorithms
along with the text for transformation.
When the message reaches the destination,
this system at the other end decrypts the cipher text into original message
with the help of the key.
This is called as Decryption System.
The output of the Decryption System is the intended message.
Depending on how the keys are shared,
we can classify crytography as symmetric and asymmetric.
If the keys used by both parties are same,
then it is called symmetric key cryptography, or private key cryptography.
If both parties use different keys for encyrption and decryption,
then it is called asymmetric key cryptography or public key cryptography.
