# Security+™ Practice Questions

## Cryptographic algorithms

Q5. 3DES (Tripple Data Encryption Standard) is based on which of the following?

A. Hashing algorithm

B. Symmetric key-based algorithm

C. Asymmetric key-based algorithm

D. None of these

Explanation:

There are three types of cryptographic algorithms that are commonly used. They are:

I. Hashing algorithms

II. Symmetric key-based algorithms

III. Asymmetric key-based algorithms

I. Hashing algorithms: Hashing is not an encryption scheme, but ensures that the transmitted data is not tampered with. Common hash algorithms include the following:

1. Secure Hash Algorithm (SHA, SHA-1): Developed by NSA, SHA-1 can generate a 160-bit hash from any variable-length string of data.

2. MD4, MD5: MD series of encryption algorithms generate a hash of up to 128-bit strength out of any length of data.

II. Symmetric algorithms: As the name suggests, symmetric key algorithms use the same key to encrypt as well as decrypt message. Some of the commonly used symmetric key algorithms are:

DES (Data Encryption Standard): DES uses a 56-bit key on each 64-bit chunk of data. It is limited in used due to its short key length.

3DES (Tripple DES): 3DES greatly improves the the security by providing three distinct keys. The total bit strength is 168 bits.

AES (Advanced Encryption Standard): AES is successor to DES, and can create keys from 128-bit to 256-bit length.

Blowfish Encryption Algorithm: It is another flexible, and secure symmetric encryption algorithm. It can perform encryption with encryption key length up to 448 bits. It can encrypt any length of data chunk.

IDEA (International Data Encryption Algorithm): It can encrypt 64-bit blocks of data and uses a 128-bit strength encryption key.

RC5, RC6 (Rivest Cipher): These are the most commonly used encryption security ciphers.

III. Assymetric algorithms: Also known as public key algorithms, these algorithms use asymmetric keys for encoding and decoding a message. Given below are some of the popular asymmetric algorithms:

RSA algorithm: Widely used for encryption and digital signatures. Uses public key and private key for encryption and decryption.
Deffie-hellman Key Exchange: This is one of the early key exchange algorithm.
Elliptic Curve Cryptography (ECC): This another form of asymmetric key algorithm. One advantage of ECC algorithm is that they have very compact, and more efficient compared to RSA