**Symmetric key encryption** uses same key, called secret key, for both encryption and decryption. Users exchanging data keep this key to themselves. Message encrypted with a secret key can be decrypted only with the same secret key. The algorithm used for symmetric key encryption is called secret-key algorithm. Since secret-key algorithms are mostly used for encrypting the content of the message they are also called content-encryption algorithms. **Symmetric-key algorithms** are a class of algorithms for cryptography that use trivially related, often identical, cryptographic keys for both decryption and encryption.

**Symmetric Encryption** is a type of encryption where the same secret key is used to encrypt and decrypt information. A secret key can be a number or a word or just a string of random characters. Secret key is applied to the information to change the content in a particular way. The other names for Symmetric Encryption are symmetric key encryption, single key encryption, one-key encryption and private key encryption.

## Types of Symmetric Encryption Algorithms

- Stream Ciphers – Stream ciphers encrypt the bits of information one at a time. These are faster and smaller to implement than Block Ciphers. Stream ciphers operate on 1bit of data at a time. If the same key stream is used, attacks may cause the information to be revealed.
- Block Ciphers – Block ciphers encrypt the information by breaking down into blocks. The blocks are of fixed size commonly of 64 bits. The commonly used block ciphers are Triple DES and AES.

### List of Symmetric Encryption Algorithms

- Advanced Encryption Standard (AES) Encryption Algorithm
- Blowfish Encryption Algorithm
- Two fish Encryption Algorithm
- Carliste Adams and Stanfford Tavares
- Data Encryption Standard
- International Data Encryption Algorithm
- Serpent Encryption Algorithm
- Triple Data Encryption Standard etc.

## Advantages and Limitations of Symmetric Encryption Algorithms

- Advantages of Symmetric Encryption Algorithms
- Symmetric Encryption Algorithm provides high security [security is dependent on the length of the key].
- Symmetric Encryption Algorithm encrypts the data at high speeds.
- The Encryption process is simple.

- Limitations of Symmetric Encryption Algorithms
- The shared secret key must be agreed by both the parties.
- Authenticity cannot be proved as the secret key is shared.
- Symmetric key management in symmetric key algorithm is problematic.

There are a few vulnerabilities in **Symmetric Encryption Algorithms**. Breaking symmetric encryption by brute force and cryptanalysis. Exchanging and Storing of Secret keys should be done securely in order to avoid attacks. In case of forgotten passwords, we cannot decrypt the data that you have encrypted.

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