Last Updated on July 31, 2021 by Admin

## Which type of algorithm encrypts data bit by bit?

- block
- asymmetric
- stream
- symmetric

**Explanation:**

Stream ciphers operate bit by rather on a block of data at a time. Stream and block ciphers are the two main types of symmetric algorithms.

Block ciphers process one block of bits, and stream ciphers process one bit at a time. RC5 and RC6 are block ciphers.

Symmetric ciphers are those that use the same key to encrypt as to decrypt. Symmetric ciphers have modes of operation: ECB, CBC, CTM or CTR, and GCM.

– Electronic Code Book (ECB) mode implements the cipher in its original form.

– Cipher-block Chaining (CBC) mode uses the output of each block and XORs it with the following block to increase diffusion.

– Counter Mode (CTM or CTR) converts a block cipher into a stream cipher.

– Galois Counter Mode (GTM) uses a hash function to further complicate the encryption.

Asymmetric cryptography involves the use of different keys to encrypt and decrypt the data. These keys are referred to as private and public keys, respectively. The public encryption key is used to ensure only the intended recipient the cipher text. 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. ElGamal is an asymmetric public key encryption algorithm based on the Diffie-Hellman key agreement.

Block ciphers operate on a block of data at a time rather than bit by bit.

**Objective**: Cryptography

**Sub-Objective**: Compare and contrast symmetric and asymmetric encryption algorithms