Figure 1.1: Cryptography at work

The plaintext which is sent by the sender through the wire is encrypted into

ciphertext, which then is decrypted into plaintext for the recipient to

receive. To encrypt and decrypt the message, the same shared secret key is

used.

Cryptography’s primary functions are as follows:

Privacy and confidentiality ensure that no one other than the intended

receiver can read the message.

The process of authentication ensures proving one’s identity.

The message has not been altered in any way from the original is

assured to the receiver receiving the message by integrity.

The sender really sent this message is proven by the mechanism of

non-repudiation.

The method used by crypto keys that are shared between the sender

and the receiver is key exchange.

Starting with the unencrypted data, referred to as plaintext in cryptography,

the plain text is encrypted into ciphertext, which in turn will be decrypted

back into plaintext. The encryption and decryption done are based on the

type of cryptography scheme used and the form of the key.

The process is,

C = Ek(P)

P = Dk(C)

Where P = plaintext, C = ciphertext, E = the encryption method used, D =

the decryption method used, and k = the key.