science

SOBER

SOBER 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 SOBER rather than just read about it. In short: In cryptography, SOBER is a family of stream ciphers initially designed by Greg Rose of QUALCOMM Australia starting in 1997. The name is a contrived acronym for Seventeen Octet Byte Enabled Register.

Key takeaways

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

Reference excerpt

In cryptography, SOBER is a family of stream ciphers initially designed by Greg Rose of QUALCOMM Australia starting in 1997. The name is a contrived acronym for Seventeen Octet Byte Enabled Register. Initially the cipher was intended as a replacement for broken ciphers in cellular telephony. The ciphers evolved, and other developers (primarily Phillip Hawkes) joined the project. SOBER was the first cipher, with a 17-byte linear-feedback shift register (LFSR), a form of decimation called stuttering, and a nonlinear output filter function. The particular configuration of the shift register turned out to be vulnerable to "guess and determine" attacks. SOBER-2 changed the position of the feedback and output taps to resist the above attacks. S16 was an expansion to 16-bit words rather than bytes, with an expected increase of security.

Adaptions for and since NESSIE For the NESSIE call for new cryptographic primitives, three new versions called the t-class were developed; SOBER-t8 was virtually identical to SOBER-2 but did not have sufficient design strength for NESSIE submission; SOBER-t16 and SOBER-t32 were submitted. t32 was a further expansion to 32-bit words, while both ciphers had a more efficient method of computing the linear feedback. Subsequent to NESSIE, SOBER-128 was designed to take into account what had been learned. The stuttering was dropped because it added too little strength for the overhead, and the nonlinear output function was strengthened. As a stream cipher, SOBER-128 remains unbroken. The message authentication capability that was added at the same time was trivially broken.

Mundja An integrated message authentication feature based on SHA-256 that was designed to be added to stream ciphers such as SOBER-128. Turing Named after Alan Turing, shares the LFSR design of SOBER-128, but has a block-cipher-like output filter function with key-dependent S-boxes, and remains unbroken subject to a minor usage constraint. NLS Short for Non-Linear SOBER, it was submitted to the European eSTREAM project. It uses nonlinearity for the shift register, and simplifies the output filter for increased performance, using Mundja for message authentication. SSS, for Self-Synchronizing SOBER, was also submitted but has very little relationship to the other SOBER ciphers, and was quickly broken. Shannon Named after Claude Shannon, shortens the register to 16 32-bit words, and has completely new feedback and output filter tap positions. It incorporates a new and more efficient message authentication mechanism. Boole Named after George Boole, is a family of combined hash functions and stream ciphers that were developed for submission to the NIST call for development of an advanced hash standard, but were withdrawn when a collision was discovered.

References

External links QUALCOMM Australia Archived 2015-03-22 at the Wayback Machine – info on the whole SOBER family NIST – NIST call for an Advanced Hash Standard

Worked examples

Example 1 — a first encounter with SOBER

Start with the simplest possible case. Write down what SOBER 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 SOBER 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 SOBER 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 SOBER

In research: SOBER 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 SOBER 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: SOBER is common in secondary-school and first-year university syllabi. It links to neighbouring topics Stream ciphers, so understanding it makes those chapters shorter.
In everyday life: Look for SOBER 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.

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How to study SOBER in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what SOBER 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 SOBER out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is SOBER in simple terms?

In cryptography, SOBER is a family of stream ciphers initially designed by Greg Rose of QUALCOMM Australia starting in 1997. The name is a contrived acronym for Seventeen Octet Byte Enabled Register.

Why does SOBER 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 SOBER?

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 SOBER.