Question

A cryptographic hash algorithm is a one-way function; information processed with such a hash algorithm cannot later be recovered. Name one use for a cryptographic hash and briefly explain how the hash is used in your example. (There are several uses; I only want one of them.)

Describe what must happen with respect to public keys for a ""man-in-the-middle attack"" to succeed when messages are encrypted using public key cryptography.

Answer 1

A cryptographic hash is used to verify data integrity by comparing the hash value of received data with the expected value. For a 'man-in-the-middle attack' to succeed, the attacker must intercept and replace the public key exchanged between sender and receiver without being detected.

Step-by-step explanation:

One use for a cryptographic hash is to verify the integrity of data. For example, software developers often provide a hash value along with downloadable files. After downloading the file, a user can run a hash algorithm on it to produce a hash value. If this value matches the one provided by the developer, it assures the user that the file has not been tampered with and is exactly as the developer intended.

For a 'man-in-the-middle attack' to succeed in the context of public key cryptography, the attacker must intercept the public key sent from the supposed sender to the intended receiver. The attacker then substitutes it with their own public key without the receiver knowing. When the receiver encrypts a message using the attacker's public key, the attacker can decrypt it, read or modify it, then re-encrypt it with the intended recipient's actual public key and send it on, without either the sender or receiver being aware of the compromise.