computer science

OpenPuff

OpenPuff is a computer 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 OpenPuff rather than just read about it. In short: OpenPuff Steganography and Watermarking, sometimes abbreviated OpenPuff or Puff, is a free steganography tool for Microsoft Windows created by Cosimo Oliboni and still maintained as independent software. The program is notable for being the first steganography tool (version 1.01 released in December 2004) that: lets users hide data in more than a single carrier file.

Key takeaways

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

Reference excerpt

OpenPuff Steganography and Watermarking, sometimes abbreviated OpenPuff or Puff, is a free steganography tool for Microsoft Windows created by Cosimo Oliboni and still maintained as independent software. The program is notable for being the first steganography tool (version 1.01 released in December 2004) that:

lets users hide data in more than a single carrier file. When hidden data are split among a set of carrier files you get a carrier chain, with no enforced hidden data theoretical size limit (256MB, 512MB, ... depending only on the implementation) implements 3 layers of hidden data obfuscation (cryptography, whitening and encoding) extends deniable cryptography into deniable steganography Last revision supports a wide range of carrier formats:

Images Bmp, Jpg, Png, Tga Audios Aiff, Mp3, Wav Videos 3gp, Mp4, Mpeg I, Mpeg II, Vob Flash-Adobe Flv, Pdf, Swf

Use OpenPuff is used primarily for anonymous asynchronous data sharing:

the sender hides a hidden stream inside some public available carrier files (password + carrier files + carrier order are the secret key) the receiver unhides the hidden stream knowing the secret key The advantage of steganography, over cryptography alone, is that messages do not attract attention to themselves. Plainly visible encrypted messages — no matter how unbreakable — will arouse suspicion, and may in themselves be incriminating in countries where encryption is illegal. Therefore, whereas cryptography protects the contents of a message, steganography can be said to protect both messages and communicating parties. Watermarking is the action of signing a file with an ID or copyright mark. OpenPuff does it in an invisible steganographic way, applied to any supported carrier. The invisible mark, being not password protected, is accessible by everyone (using the program).

Multi-cryptography OpenPuff is a semi-open source program:

cryptography, CSPRNG, hashing (used in password hexadecimal extension), and scrambling are open source Cryptographic algorithms (16 taken from AES, NESSIE and CRYPTREC) are joined into a unique multi-cryptography algorithm:

keys and internal static data are initialized for each algorithm f each data block D [ i ] (128bit) will be encrypted using a different algorithm f [ i ] f [ i ] is chosen with a pseudorandom oracle, seeded with a second independent password 1. Choosing the cryptography algorithm for data block i f [ i ] = rand ( Oracle )

2. Applying cryptography to data block i Cipher ( D [ i ] ) = f [ i ] ( D [ i ] )

Statistical resistance Extensive testing has been performed on the statistical resistance properties of the CSPRNG and multi-cryptography modules, using the ENT, NIST and DIEHARD test suites. Provided results are taken from 64KB, 128KB, ... 256MB samples:

bit entropy test: >7.9999xx / 8.000000 compression test: 0% size reduction after compression chi square distribution test: 40% < deviation < 60% mean value test: 127.4x / 127.5 Monte Carlo test: error < 0.01% serial correlation test: < 0.0001

Steganalysis resistance Security, performance and steganalysis resistance are conflicting trade-offs. [Security vs. Performance]: Whitening

Pro: ensures higher data security Pro: allows deniable steganography Con1: requires a lot of extra carrier bits [Security vs. Steganalysis]: Cryptography + Whitening

Pro: ensure higher data security Con2: their random statistical response marks carriers as more "suspicious" Data, before carrier injection, is encrypted and whitened: a small amount of hidden data turns into a big chunk of pseudorandom "suspicious data". Carrier injection encodes it using a non linear covering function that takes also original carrier bits as input. Modified carriers will need much less change (Con1) and, lowering their random-like statistical response, deceive many steganalysis tests (Con2).

Deniable steganography There will always be a non-negligible probability of being detected, even if the hidden stream behaves like a "natural container" (unpredictable side-effects, being caught in Flagrante delicto, etc.). Resisting these unpredictable attacks is also possible, even when the user is forced (by legal or physical coercion) to provide a valid password. Deniable steganography (a decoy-based technique) allows the user to deny convincingly the fact that sensitive data is being hidden. The user needs to provide some expendable decoy data that he would plausibly want to keep confidential and reveal it to the attacker, claiming that this is all there is.

Illustrations

Worked examples

Example 1 — a first encounter with OpenPuff

Start with the simplest possible case. Write down what OpenPuff claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer 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 OpenPuff 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 OpenPuff 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 OpenPuff

In research: OpenPuff appears in computer 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 OpenPuff 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: OpenPuff is common in secondary-school and first-year university syllabi. It links to neighbouring topics 2004 software, Applications of cryptography, Cryptographic software, so understanding it makes those chapters shorter.
In everyday life: Look for OpenPuff 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 OpenPuff in 20 minutes

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

Frequently asked questions

What is OpenPuff in simple terms?

Why does OpenPuff matter?

Because it connects several computer 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 OpenPuff?

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 OpenPuff.