Secret key Algorithms in Cryptography

We know that always could have any bugs related to security functions in any software. So, system architects have found different strategies called defense in depth to protect from unauthorized access. These mechanisms can frustrate attackers. What is cryptography, It comes from two words. There are ‘crypto’ and ‘graphy’. This means secret writing. You can use a cipher to make information secret. We can convert plain text to cipher text using an algorithm. The encryption is the process of making text secret. The decryption is the reverse processing of encryption.

In the past, cipher has been used before coming to computers. Julius caesar has been used a cipher to share messages call Caesar cipher. They used the substitution cipher method, which replaces one letter to another letter. A => G, F => L like that. This pattern knows only the sender and receiver. Thus, others cannot read directly what about called this message. But, this was insecure, because it can easily read using more technique and imaging letters like frequently user letters in English. After years, came columnar transmission cipher. They fill the letters into the grid and read different orders to encrypt the message. After years came the German Engima used to communicate messages in wartime. 3 rotor has electrical contacts for all 26 letters and they connect with each electrical contact with a different order like one letter to another.

In this here you can see they used the reflector to transform one letter to another letter when we type. Here you can see when we type the letter b convert to letter f. This called encryption. If we think after this message sends to the receiver, he just wants to type that ciphertext again using another same machine(same configuration with sender machine), then that machine displays correct plain text to the receiver easily. That called decrypt.

After a couple of years, cryptography moved from hardware into software. In this here, you can see the Data Encryption Standard developed by IBM.

• Here, Messages are encrypted using the same key both encryption and decryption.
• We call this as private key encryption or secrete key.

This has many disadvantages:

• If any person gets this secrete key, he can decrypt that encrypted messages easily.
• As well as, we want to share the secret key to the receiver.

• Two methods are used in symmetric key encryption. There are Stream cipher and Block cipher.
• The stream cipher is message encryption that uses a single bit at a time. This method don’t use in modern cryptography. RC4 (Rivest Cipher 4) used this method.
• The block cipher encrypt data on fixed-length like a group of bits. It called as blocks. It always encrypts data in a certain certain length. Examples are DES, Triple DES, RC5 (Rivest Cipher 5), AES (Advanced Encryption Standard), and Blowfish.