Exam JN0-336 Topic 1 Question 37 Discussion

The correct answers are B and D. In VPN cryptography, hashing is used for authentication and integrity checking, not confidentiality. Juniper's IPsec documentation describes MD5 as producing a 128-bit hash, also called a digital signature or message digest, from a message of arbitrary length. It also describes SHA as producing a 160-bit hash from a message of arbitrary length. That directly supports option B because a hash function takes variable-length input and produces a fixed-size digest.
Option D is also correct because Juniper states that the resulting hash is used like a fingerprint of the input to verify content and source authenticity and integrity. Juniper's IPsec overview further explains that Junos compares the calculated message digest against the expected digest to verify that the message has not been tampered with.
Option A is wrong because hashing is not compression; it is one-way digest generation. Option C is wrong because encryption protects confidentiality, while hashing validates integrity and authenticity. In IPsec, algorithms such as AES, DES, and 3DES provide encryption, while MD5, SHA-1, and SHA-2 provide hashing/HMAC-based authentication. Reference topics: IPsec VPN, hashing, HMAC, MD5, SHA, message digest, data integrity.