Cisco Certified Network Associate (CCNA) Practice Exam

Which hash function produces a 160-bit hash value and is widely used in SSL and IPsec?

1. Message Digest 5 (MD5)

2. Secure Hash Algorithm (SHA)

3. Rivest Hash Function (RH)

4. SHA-256

The correct answer is: Secure Hash Algorithm (SHA)

The correct answer is the Secure Hash Algorithm (SHA), which produces a 160-bit hash value, specifically in the case of SHA-1. This hash function is indeed widely utilized in various security protocols, including SSL (Secure Sockets Layer) and IPsec (Internet Protocol Security). SHA-1 plays a significant role in ensuring data integrity and authenticity in digital communications. When a message is transmitted over a network, the corresponding hash value is calculated and sent along with it. The recipient can then use the same hash function on the received message to verify that the message has not been altered during transmission. While there are other hash functions mentioned, such as MD5, it produces a 128-bit hash value, which is less secure compared to SHA-1's 160-bit output. The Rivest Hash Function is not specifically recognized as a standard hash function used in SSL/IPsec, and SHA-256, while being a member of the SHA family, produces a 256-bit output, which is larger than the specified 160-bit requirement. Thus, SHA stands out as the function that fits the criteria outlined in the question.