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## Which of the following are symmetric encryption algorithms? (Select 3 choices.)

- AES
- RC4
- 3DES
- ECC
- DH
- DSA

**Explanation:**

Advanced Encryption Standard (AES), RC4, and Triple Data Encryption Standard (3DES) are symmetric encryption algorithms. When symmetric encryption algorithms are used, the same encryption key is used to encrypt and decrypt data. In addition, because symmetric encryption algorithms use less complex mathematics than asymmetric encryption algorithms when encrypting and decrypting data, they often perform faster than asymmetric encryption algorithms.

Two types of symmetric encryption algorithms exist: block ciphers and stream ciphers. Block ciphers derive their name from the fact that they encrypt fixedlength blocks of data. For example, AES encrypts 128bit blocks of data. By contrast, stream ciphers are typically faster than block ciphers because stream ciphers can encrypt text of variable length depending on the size of the frame to be encrypted? stream ciphers are not limited to specific block sizes. For example, RC4, a stream cipher, can encrypt data in streams of 8 through 2,048 bits. Other examples of symmetric encryption algorithms include International Data Encryption Algorithm (IDEA), Skipjack, and Blowfish.

DiffieHellman (DH), Digital Signature Algorithm (DSA), and Elliptical Curve Cryptography (ECC) are asymmetric algorithms. DH is an asymmetric key exchange method. DSA and ECC are asymmetric encryption algorithms. Asymmetric encryption, also known as public key encryption, uses a public key to encrypt data and a different, yet mathematically related, private key to decrypt data. Public key infrastructure (PKI) uses a certificate authority (CA) to tie a public key to a user ID to further ensure the confidentiality of data. Other examples of asymmetric encryption algorithms include RSA and ElGamal.

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