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## Which of the following is the most widely used public key cipher?

- 3DES
- EI Gamal
- RSA
- AES

**Explanation**:

Rivest, Shamir, Adleman (RSA) is the most widely used public key or asymmetric cipher. RSA supports encryption and decryption and secures data with an algorithm that is based on the difficulty of factoring large numbers.

A public key encryption algorithm is sometimes referred to as an asymmetric encryption algorithm. With asymmetric encryption, the public key is shared and used to encrypt information, and the private key is secret and used to decrypt data that was encrypted with the matching public key. Using RSA, messages travelling between two points are encrypted and authenticated. RSA tokens are used to provide a rolling password for one-time use.

Triple DES or 3DES is a symmetric algorithm, which means the key used to encrypt is identical to the key used to decrypt. Triple DES is a later version of Data Encryption Standard (DES) that performs three rounds of encryption. The encryption and decryption process performed by 3ES takes longer due to the higher processing power required.

While EI Gamal is a public key or asymmetric cipher, it is not the most widely used.

AES is a symmetric algorithm that is currently the best encryption algorithm available commercially.

Advanced Encryption Algorithm that is currently the best encryption algorithm available commercially. The Advanced Encryption Standard (AES) uses 128-bit, 192-bit, and 256-bit encryption keys.

**Objective**: Cryptography

**Sub-objective:** Describe the security impact of these commonly used encryption algorithms and secure communications protocols: DES, 33DES, AES, AES256-CTR, RSA, DSA, SSH, SSL/TLS.

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