# Notes On Encryption Algorithms

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Chapter: Literature Survey________________________________________
Encryption Algorithms:
The broad-spectrum of encryption algorithm comprises of two mathematical revolutions: an encryption function E, and a decryption function D = E¬¬-1. For secure communication between the sender and receiver, the sender (conventionally called Alice) will apply the encryption function to the actual message P (the plaintext), and pass on the resulting cipher text C = E (P) over the anxious channel. Once the cipher text (C) is received by the anticipated recipient (called Bob), the plaintext is mended by computing D(C) = P. Different kind of encryption techniques is as follows.

Symmetric Key Cryptography:
Symmetric Encryption is a one of the technique in cryptography for encrypting the text, images etc. The method of encryption and decryption in Symmetric cryptography hang on the secret key, which is shared between the two parties (i.e. Sender and Receiver).

Secrete Key(K)

Plain Text (P) Cipher Text (C) Plain Text (P)

Figure 1: Model for Symmetric Encryption

The Symmetric Encryption model has five components (see Figure 1)

Plaintext (P): This is the actual comprehensible message or data. It served as input to the Encryption Algorithm (E).
Encryption Function (E): The main task of encryption Function is to perform the permutation and substitutions on the plain text.
Secret Key (K): Secret key is used to encrypt the plain text . It is also input to the encryption function. In symmetric key encryption, only one key is used between sender and receiver. This secret key will shared by both using the secured channel.
Cipher text (C): Cipher text will get afte...

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...integrity and secrecy.
Electronic Codebook Mode (ECB):
The ECB mode is one of the techniques to encrypt the message. Here message is simply divided into n-bit blocks, each block is encrypted individually.

Figure 3.1: a) ECB mode encryption b) ECB mode decryption
The main advantages of this mode are simplicity and its correctness for parallel processing. The encryption and decryption are performed separately for arbitrary position blocks, for that error do not promulgate from one block to another. The major drawback of this methodology is that, in plaintext, it does not hide all patterns i.e.., if plaintext contains identical blocks, then cipher text will get the same identical pattern of blocks without any modification or changes in the cipher text. In all cases it doesn’t provide the message confidentiality.