Hashing is not only for storing passwords. Because a cryptographic hash produces a short, fixed-size fingerprint that changes drastically when even one bit of input changes, hashes are the standard tool for answering the question "is this data exactly what it was supposed to be?" In this topic you will see that idea applied to downloaded files, messages in transit, and software distributed by vendors.
The key distinction to keep in mind is what each mechanism actually proves. A plain checksum or file hash detects accidental corruption and, if the published hash comes from a trustworthy source, lets you spot a tampered download. An HMAC adds a shared secret key, so only someone holding that key can produce or verify the tag — this gives integrity plus authentication between two parties. A digital signature uses a private key to sign a hash of the message, so anyone with the corresponding public key can verify both integrity and origin, and the signer cannot credibly deny having signed it.
As you watch, look for three things: where the hash function sits in each workflow (what exactly is being hashed), what secret or key material is involved, and what threat each mechanism does and does not defend against. Those three questions are the backbone of the comparison you will be asked to make between checksums, HMACs, and digital signatures.
A concise lesson from the CompTIA Security+ SY0-701 certification course covering hashing and digital signatures. Based on the exam objective it addresses, it should introduce hash functions and their properties, show how hashes are used to confirm that data has not changed, and then explain how signing a hash with a private key produces a digital signature that others verify with the public key. Expect coverage of related concepts such as collisions and salting as they appear in the Security+ objectives.
Professor Messer is a long-established, well-regarded producer of certification training, and this video maps directly onto the integrity-verification and digital-signature subtopics in a tightly organized ten minutes.
This video walks step by step through how public key cryptography and hashing combine to produce a digital signature. Its description indicates a focus on how signing provides authenticity and integrity protection, so expect a walkthrough of the sender hashing a message, signing the hash with a private key, and the recipient verifying with the public key.
It gives a slower, diagram-driven treatment of the signature workflow that complements the faster certification-style overview, reinforcing exactly why the hash step is essential to signing.
A practical, consumer-oriented video on checking file hashes when you download software. It should demonstrate how to compute a hash of a downloaded file, compare it against the value published by the vendor, and explain why a mismatch matters — the everyday application of checksums to software distribution integrity.
This is the hands-on counterpart to the theory videos: it turns the checksum subtopic into something you can actually do, and it surfaces the practical caveats about trusting the published hash.
Together these videos target MO4 most directly: the ThioJoe walkthrough makes checksum-based software distribution verification concrete, while the Professor Messer and LearnCantrill videos build the digital signature half of the picture, including the HMAC and keyed-authentication ideas that support MO3. The Security+ lesson also reinforces MO1 by revisiting core hash properties such as collisions and the role of hashing versus encryption. After watching, you should be able to place checksums, HMACs, and digital signatures on a spectrum of increasing guarantees and justify which one fits a given real-world scenario.
These videos were chosen from YouTube on October 2, 2026. Each has captions; the player turns them on. Videos on YouTube can be changed or removed — if one no longer plays, tell your instructor. If a player does not appear, use its Watch on YouTube link.