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Intermediate Topic 18 of 51 Security & Cryptography

SHA Family

Standard cryptographic hash algorithms.

How it works

The Secure Hash Algorithm family, standardized by NIST, includes SHA-1, with 160-bit output and now broken for collisions, the SHA-2 group, SHA-224, SHA-256, SHA-384 and SHA-512, built with the Merkle-Damgard construction, and SHA-3, based on the Keccak sponge construction chosen in a public competition. SHA-256 is the workhorse for certificates, Bitcoin and integrity checking, and SHA-3 offers a different internal design in case SHA-2 is weakened.

Step-by-step walkthrough

  1. Any input of any size goes in.
  2. The data is processed in blocks through many rounds.
  3. A fixed-size digest comes out.
  4. A tiny change in the input flips about half the bits.
  5. It is one-way and collision resistant, and used for integrity checks.

Where it is used

TLS certificates, digital signatures, HMAC, Git, package managers and blockchain proofs of work use SHA functions.

Common pitfall

SHA-1 and MD5 collisions have been demonstrated and exploited, for instance in forged certificates, so migrate away. SHA-2 is vulnerable to length-extension attacks when used naively as a keyed hash; use HMAC or SHA-3. Do not use any plain SHA function for storing passwords. Choose output size to match the security level needed.

Where it fits in the course

SHA Family is topic 18 of 51 in Security & Cryptography, rated Intermediate. It follows Hash Functions. The next topic is Digital Signatures.

Practice and explore

How to study this topic

  1. Read the explanation above and restate the definition in your own words.
  2. Open the interactive lesson and answer its mini quiz.
  3. Read the common pitfall, then write a short example that avoids it.
  4. Check your understanding in the Security & Cryptography quiz, and revisit the topic if you miss a question.

Frequently asked questions

What is SHA Family?
Standard cryptographic hash algorithms. It belongs to Security & Cryptography and is an intermediate-level topic.
Where do people use SHA Family?
TLS certificates, digital signatures, HMAC, Git, package managers and blockchain proofs of work use SHA functions.
What is the most common mistake with SHA Family?
SHA-1 and MD5 collisions have been demonstrated and exploited, for instance in forged certificates, so migrate away.
What should I learn before this topic?
Start with Hash Functions, the topic just before it in Security & Cryptography.
How can I practice it?
Answer the mini quiz in the interactive lesson, then take the Security & Cryptography quiz.
Is SHA Family hard to learn?
It is an Intermediate topic. Be comfortable with the Beginner topics in this area first, then read the common pitfall carefully, since it is where most mistakes happen.
How long does it take to learn SHA Family?
Most learners can read the explanation and finish the interactive lesson in under an hour. Fluency comes from applying the idea, so plan a few short practice sessions with the quiz.
Which topics are related to SHA Family?
Hash Functions, Digital Signatures, RSA are closely connected. The full list is in the related topics section of this page.
What should I study after SHA Family?
Continue with Digital Signatures, the next topic in Security & Cryptography.

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