### RC4

RC4 is known as the most popular symmetric stream ciphers in symmetric cryptography. With the random key generated by pseudorandom byte generator and with the input as a key K, a stream of 8 bits is generated, which is applied on a plaintext of individual bits or a byte at a time. Without the knowledge of input key K it is impossible to predict the pseudorandom generated key stream.

** DES**

- DES is a cipher or encryption algorithm which came into picture in the 1970’s.
- The algorithm uses the Fiestel structure for encryption of the information; it uses 16 rounds of XOR operations. The encryption and decryption are carried out using sub keys which implement XOR and reverse XOR respectively.
- DES used relatively smaller key size for encryption, which made it less secured when compared to the other algorithms. Hence triple DES and AES were implemented later which were more secured.
- 3DES or Triple DES overcomes the drawbacks of the DES algorithm and was adopted as aUSstandard in 1977. 3DES uses three 64-bit long keys for encryption. Data encryption using TDES, is encrypted with the first key, decrypted with the second key, and finally encrypted again with the third key, which makes the key length to 192 bits.
- TDES uses three steps of encryption to avoid the meet-in-the-middle-attacks, which are quiet common in double DES encryption. TDES also has a large key space than the 56 bit key of DES to secure against the brute force attacks.
- In order to simplify interoperability between DES and TDES the middle step is usually decrypted (EDEmode): DES (k3; DES-1(K2; DES (k1; M))) where M is the message block and k1, K2, k3 as DES keys.

This Project Paper is written & submitted by **Deepak V****.**