science

Hierocrypt

Hierocrypt is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Hierocrypt rather than just read about it. In short: In cryptography, Hierocrypt-L1 and Hierocrypt-3 are block ciphers created by Toshiba in 2000. They were submitted to the NESSIE project, but were not selected.

Key takeaways

Hierocrypt belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Hierocrypt to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hierocrypt from memory before moving on to harder problems.

Reference excerpt

In cryptography, Hierocrypt-L1 and Hierocrypt-3 are block ciphers created by Toshiba in 2000. They were submitted to the NESSIE project, but were not selected. Both algorithms were among the cryptographic techniques recommended for Japanese government use by CRYPTREC in 2003, however, both have been dropped to "candidate" by CRYPTREC revision in 2013. The Hierocrypt ciphers are very similar, differing mainly in block size: 64 bits for Hierocrypt-L1, 128 bits for Hierocrypt-3. Hierocrypt-L1's key size is 128 bits, while Hierocrypt-3 can use keys of 128, 192, or 256 bits. The number of rounds of encryption also varies: Hierocrypt-L1 uses 6.5 rounds, and Hierocrypt-3 uses 6.5, 7.5, or 8.5, depending on the key size. The Hierocrypt ciphers use a nested substitution–permutation network (SPN) structure. Each round consists of parallel applications of a transformation called the XS-box, followed by a linear diffusion operation. The final half-round replaces the diffusion with a simple post-whitening. The XS-box, which is shared by the two algorithms, is itself an SPN, consisting of a subkey XOR, an S-box lookup, a linear diffusion, another subkey XOR, and another S-box lookup. The diffusion operations use two MDS matrices, and there is a single 8×8-bit S-box. The key schedule uses the binary expansions of the square roots of some small integers as a source of "nothing up my sleeve numbers". No analysis of the full ciphers has been announced, but certain weaknesses were discovered in the Hierocrypt key schedule, linear relationships between the master key and some subkeys. There has also been some success applying integral cryptanalysis to reduced-round Hierocrypt variants; attacks faster than exhaustive search have been found for 3.5 rounds of each cipher.

References

External links 256bit Ciphers - HIEROCRYPT Reference implementation and derived code

Worked examples

Example 1 — a first encounter with Hierocrypt

Start with the simplest possible case. Write down what Hierocrypt claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hierocrypt before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hierocrypt ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hierocrypt

In research: Hierocrypt appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Hierocrypt in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Hierocrypt is common in secondary-school and first-year university syllabi. It links to neighbouring topics Block ciphers, so understanding it makes those chapters shorter.
In everyday life: Look for Hierocrypt outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Hierocrypt in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hierocrypt means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Hierocrypt out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hierocrypt in simple terms?

In cryptography, Hierocrypt-L1 and Hierocrypt-3 are block ciphers created by Toshiba in 2000. They were submitted to the NESSIE project, but were not selected.

Why does Hierocrypt matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hierocrypt?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hierocrypt.