On which of the following, digital signatures are based? Each correct answer represents a complete solution. Choose two.

A.
RADIUS

B.
Hashing functions

C.
Symmetric encryption

D.
Asymmetric encryption

Explanation:
Digital signatures are based on hashing functions and asymmetric encryption. Both encryption methods play an important role in signing of digital documents. A digital signature is a technique to authenticate digital documents by using computer cryptography. A digital signature not only validates the sender’s identity, but also ensures that the document’s contents have not been altered. It verifies that the source and integrity of the document is not compromised since the document is signed. A digital signature provides the following assurances:
Authenticity, Integrity, and Non-repudiation. Microsoft Office 2007 Excel and Word provide a feature known as Signature line to insert a user’s digital signature on a document.
What is asymmetric encryption?
Asymmetric encryption is a type of encryption that uses two keys – a public key and a private key pair for data encryption. The public key is available to everyone, while the private or secret key is available only to the recipient of the message. For example, when a user sends a message or data to another user, the sender uses a public key to encrypt the data. The receiver uses his private key to decrypt the data.
Answer option C is incorrect. Digital signatures are not based on RADIUS. What is Remote Authentication Dial In User Service (RADIUS) ? Remote Authentication Dial In User Service (RADIUS) is a networking protocol that provides centralized access, authorization and accounting management for people or computers to connect and use a network service. When a person or device connects to a network often authentication is required. RADIUS is commonly used by ISPs and corporations managing access to the Internet or internal networks employing a variety of networking technologies, including modems, DSL, wireless and VPNs.
Answer option A is incorrect. Symmetric encryption is not used by digital signature.

What is symmetric encryption?
Symmetric encryption is a type of encryption that uses a single key to encrypt and decrypt data. Symmetric encryption algorithms are faster than public key encryption. Therefore, it is commonly used when a message sender needs to encrypt a large amount of data. Data Encryption Standard (DES) uses symmetric encryption key algorithm to encrypt data.