**Symmetric-Key Cryptography** consists of a key called symmetric key, with the help of which both encryption and decryption processes are carried out. The algorithms used in the *Symmetric-key cryptography* are often termed as symmetric key ciphers or private-key ciphers or secret-key ciphers or conventional ciphers etc. In **Symmetric Key Cryptosystems**, a single key is used to encrypt and decrypt data between two communicating hosts. In order to break the system, an attacker must discover the key through trail-and-error or discover the key during the initial key agreement. **Symmetric Key Cryptography** is used for authentication and exchange of secret data on the World Wide Web.

## Modes Of Symmetric Key Cryptographic Algorithms

- Electronic codebook mode
- Cipher-Block Chaining mode
- Cipher feedback mode
- Output feedback mode

The characterization of Symmetric Key Ciphers in Symmetric-Key Cryptography is done by:

- Choice of key-space.
- Key identification within free space
- Number of cycles involved in encryption and decryption process.
- Role of Compression algorithms in adding security value.
- Choice of operations that are used in encryption or decryption process of symmetric key cryptography

In **symmetric Key cryptography**, both the sender and receiver share a same key by making use of symmetric-key ciphers. *Symmetric-key ciphers* include block ciphers and stream ciphers. A block cipher takes a block of plain text as input and outputs a block of cipher text of same size. Since messages are almost always longer than a single block, successive blocks are required for Symmetric Key Cryptography.

## Advantages of Symmetric-Key Cryptography

- Symmetric key cryptographic algorithms are faster and easier to implement.
- Symmetric key cryptography has lower overhead on system resources.
- Security is dependent on the length of the key in symmetric key cryptography.
- The encryption process of symmetric key cryptography is simple.
- By using symmetric key cryptography, each trading partner can use the same publicly known encryption algorithm, there is no need to develop and exchange secret algorithms.

## Drawbacks of Symmetric-Key Cryptography

- In Symmetric encryption method, a shared secret key must be agreed upon by both parties.
- Authenticity of origin or receipt cannot be proved because the secret key is shared in symmetric key cryptography.
- Management of the symmetric keys becomes problematic.
- If the share Symmetric key is compromised, then the attacker can easily decrypt any message that goes from the sender to the receiver.

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