science

Secrecy of correspondence

Secrecy of correspondence 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 Secrecy of correspondence rather than just read about it. In short: The secrecy of correspondence (German: Briefgeheimnis, French: secret de la correspondance) or literally translated as secrecy of letters, is a fundamental legal principle enshrined in the constitutions of several European countries. It guarantees that the content of sealed letters is never revealed, and that letters in transit are not opened by government officials, or any other third party.

Key takeaways

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

Reference excerpt

The secrecy of correspondence (German: Briefgeheimnis, French: secret de la correspondance) or literally translated as secrecy of letters, is a fundamental legal principle enshrined in the constitutions of several European countries. It guarantees that the content of sealed letters is never revealed, and that letters in transit are not opened by government officials, or any other third party. The right of privacy to one's own letters is the main legal basis for the assumption of privacy of correspondence. The principle has been naturally extended to other forms of communication, including telephony and electronic communications on the Internet, as the constitutional guarantees are generally thought to also cover these forms of communication. However, national telecommunications privacy laws may allow lawful interception, i.e. wiretapping and monitoring of electronic communications in cases of suspicion of crime. Paper letters have, in most jurisdictions, remained outside the legal scope of law enforcement surveillance, even in cases of "reasonable searches and seizures". When applied to electronic communication, the principle protects not only the content of the communication, but also the information on when and to whom any messages (if any) have been sent (see Call detail records), and in the case of mobile communication, the location information of the mobile units. As a consequence, in jurisdictions with a safeguard on secrecy of letters, location data collected from mobile phone networks has a higher level of protection than data collected by vehicle telematics or transport tickets.

United States

In the United States, there is no specific constitutional guarantee on the privacy of correspondence. The secrecy of letters and correspondence is derived through litigation from the Fourth Amendment to the United States Constitution. In an 1877 case, the U.S. Supreme Court stated:

No law of Congress can place in the hands of officials connected with the Postal Service any authority to invade the secrecy of letters and such sealed packages in the mail; and all regulations adopted as to mail matter of this kind must be in subordination to the great principle embodied in the fourth amendment of the Constitution. The protection of the Fourth Amendment has been extended beyond the home in other instances. Unlike other jurisdictions it does not protect foreigners abroad. In the Supreme Court case California v. Greenwood, protections similar to those afforded to correspondence have even been argued to extend to the contents of trash cans outside one's house, although it turned out to be unsuccessful. Like all rights derived through litigation, the secrecy of correspondence is subject to interpretation. By Supreme Court precedent, rights derived from the Fourth Amendment are limited by the legal test of a "reasonable expectation of privacy".

See also Black room Data privacy Dead letter Electronic Communications Privacy Act Katz v. United States Lawful interception Letterlocking Postal censorship Telecommunications data retention

References Act on the Protection of Privacy at the Finnish Communications Regulatory Authority site Letter to the House On the Privacy of Outbound U.S. Mail (10/18/2000) by ACLU Anuj C. Desai. The Post Office and the Birth of Communications Privacy

External links Back when spies played by the rules by David Kahn, New York Times – A history of the secrecy of letters

Illustrations

Worked examples

Example 1 — a first encounter with Secrecy of correspondence

Start with the simplest possible case. Write down what Secrecy of correspondence 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 Secrecy of correspondence 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 Secrecy of correspondence 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 Secrecy of correspondence

In research: Secrecy of correspondence 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 Secrecy of correspondence 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: Secrecy of correspondence is common in secondary-school and first-year university syllabi. It links to neighbouring topics Freedom of expression, Postal systems, Privacy, so understanding it makes those chapters shorter.
In everyday life: Look for Secrecy of correspondence 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 Secrecy of correspondence in 20 minutes

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

Frequently asked questions

What is Secrecy of correspondence in simple terms?

Why does Secrecy of correspondence 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 Secrecy of correspondence?

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 Secrecy of correspondence.